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let's see how quickly we can cover the
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main ideas found in edexel GCSE biology
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paper 1 this is good for higher end
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Foundation Tier double combined or
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triple separate that's topics 1 to five
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key Concepts cells and control genetics
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natural selection and genetic
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modification and health disease and
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medicines it's a mouthful isn't it I'll
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tell you when some of the bigger
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concepts are just for triple but not for
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higher and Foundation tier because
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there's not a lot of difference to be
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honest we're going to be really moving
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here so pause the video if you need a
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bit more time to get your head around
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something you see let's go all life
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consists of cells we can see cells with
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a normal light microscope and maybe the
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nucleus but the subcellular structures
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won't really be visible using an
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electron microscope however allows us to
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see far finer details so we can see an
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image of the organel as such these
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microscopes have a better resolving
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power and a higher resolution we say we
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can calculate the actual size of a cell
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by knowing the magnification of the
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microscope magnification is equal to
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image size divided by object size
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therefore rearranging this we can
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measure me the size of the image then
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divide by the magnification and that
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gives us the actual cell size we put
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them into two main groups eukaryotic
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cells have a nucleus in which their DNA
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is found that's your plant and animal
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cells for example procaryotic cells
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don't have a nucleus and their DNA is
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found in a ring called a plasmid both
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eukaryotic and procaryotic cells contain
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similar organel or subcellular
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structures the cell membrane keeps
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everything inside the cell but they're
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also semi-permeable which means they
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allow certain substances to pass through
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plant cells and most bacteria have an
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extra cell wall made of cellulose
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providing a rigid structure for them
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cytoplasm is the liquid that makes up
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the cell in which most chemical
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reactions take place mitochondria is
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where respiration takes place releasing
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energy for the cell to function
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ribosomes are where proteins are
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assembled or synthesized plant cells
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also contain chloroplasts which contain
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chlorophyll where photosynthesis takes
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place plant cells also contain a
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permanent vacuo in which sap is stored
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and enzymes are biological catalysts
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some of which break down larger
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molecules into smaller ones that can
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then be absorbed by the Villi and your
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small intestine into the bloodstream to
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be transported to every part of your
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body for example amalay is the enzyme
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that breaks down starch into glucose
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it's found in your small intestine and
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saliva enzymes are specific that is they
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only break down certain molecules for
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example carbohydrases break down
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carbohydrates into simple sugars amalay
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is one of these proteases break down
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proteins into amino acids and liases
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break down lipids that's fats into
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glycerol and fatty acids they're
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specific because they work on a lock and
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key principle the substrate for example
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the starch binds to the enzyme's active
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site we then call this a complex however
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this can only happen if the substrate is
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the right shape in order to fit the
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active site in reality they're
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incredibly complex shapes no pun
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intended these shapes here are just to
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represent them much like a locking key
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it only works if they're the right shape
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for each other the rate of enzyme
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activity increases with temperature due
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to to the molecules having more energy
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that is until the active site changes
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shape and so the substrate no longer
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binds we say the enzyme has denatured
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this maximum rate occurs at the optimum
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temperature Optimum meaning best this is
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similar for pH as well except it can Den
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nature too high or too low PH the
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Practical on this involves mixing amalay
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with starch at different temperatures or
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with different pH buffer Solutions once
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mixed we start timing then every 10
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seconds we remove a couple of drops and
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put in a spot in tile dimple with I in
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to begin with the iodine will turn black
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due to the still being starch present
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but eventually it will stay orange
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showing that all of the starch has been
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broken down calculate the time taken to
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do that then plot these times against pH
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or temperature draw a curved line of
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best fit and the lowest point is where
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the starch would have taken the shortest
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time to be broken down that's the
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optimum temperature or pH however in
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true biology fashion we're technically
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not allowed to interpolate between
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points for some reason so we must only
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say that the optimum pH or temperature
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is between the two lowest points shrug
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food test allow us to identify what
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nutrients are in our grub iodine turns
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from Orange to Black in the presence of
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starch like we just saw Benedict
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solution turns from Blue to Orange in
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the presence of sugars bir's reagent
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turns from Blue to purple with proteins
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cold ethanol will go cloudy with lipids
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that is fats diffusion is the movement
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of molecules or particles from an area
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of high concentration to an area of low
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concentration we say they move down the
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con concentration gradient like a ball
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just rolling down a hill it'll do it by
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itself this doesn't require any energy
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input so we say it's passive this will
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happen across a semi-permeable membrane
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if the holes are large enough for the
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molecules to move through for example
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water can pass through but glucose will
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not at least not by diffusion anyway
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osmosis is the name specifically given
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to the diffusion of water across such a
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membrane for example if there is a
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higher concentration of glucose outside
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a cell the glucose cannot diffuse in to
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balance the concentration so instead the
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water moves out of the cell resulting in
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a decrease in its mass the rate of
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diffusion on osmosis can be increased by
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increasing the difference in
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concentrations increasing the
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temperature or increasing the surface
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area this is why the Villi and your
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small intestinal lumpy as well as
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alveoli in your lungs and R hair cells
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for example too the Practical on osmosis
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goes as follows cut equal size cylinders
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from a potato or other vegetable weigh
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them and place in test tubes with
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varying concentration of sugar solution
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after a day or so we remove them dab the
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excess water off their surface and reway
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we calculate percentage change in mass
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by doing final Mass takeaway initial
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mass divided by the initial mass time
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100 if it's lighter than it was before
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this must be a negative change in mass
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we plot these percentages against sugar
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concentration and we draw a line of best
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fit where this crosses the x- axis is
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what concentration should result in no
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change in mass so no osmosis so this
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means this must be the same as the
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concentration inside the pot glucose and
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other nutrients and minerals can move
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through a membrane by active transport
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where carrier proteins use energy to
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move substances through the membrane as
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there's energy used this can actually
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move them against a concentration
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gradient for example moving mineral ions
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into plant root hair cells eukaryotic
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cell nuclei contain DNA which is stored
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in several chromosomes humans have 23
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pairs of these in every nucleus so we
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call them diploid cells that's not the
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case for gtes though they have half so
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just 23 not 23 pairs so therefore we
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call them haid cells new cells must
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constantly be made for growth and repair
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they do this by duplicating by mitosis
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here's the process the mitosis process
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the genetic material is duplicated and
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the number of ribosomes and mitochondria
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is doubled as well the nucleus breaks
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down and one set of each chromosome pair
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is pulled to opposite sides of the cell
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a new nucleus forms in each of these to
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house the copied chromosomes and we now
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have two identical cells cells
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specialize depending on the function
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they need to fulfill for example nerve
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muscle root hair xylm Flo cells stem
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cells are those that haven't yet
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specialized they're found in human and
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animal embryos and the merry stem of
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plants that's the top of the choot stem
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cells are made in your bone marrow
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throughout your life as well but these
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ones can only specialize into blood
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cells we can use them cells to combat
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conditions like diabetes and paralysis
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in fact right out of the movie the
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island people are now getting clones of
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themselves made then harvesting the stem
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cells as these won't be rejected by the
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patient personally I think this is a
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dystopian man-made horror Beyond
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Comprehension you have to weigh up the
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ethical Arguments for yourself cloning
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plants can be used to prevent species
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from becoming extinct or produce crops
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with specific characteristics our
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nervous system it consists of the CNS
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that's central nervous system that's the
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brain and spinal cord and the pns
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peripheral nervous system the nerves
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that go through the rest of the body a
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receptor for example skin detects a
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change due to a stimulus like a hot hob
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an electrical signal travels to the
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spine through sensory and relay neurons
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nerve cells the signal travels across
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the gap between these neurons called the
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sinapse by a neurotransmitter chemical
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once at the spine the signal can go to
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the brain where you can make the
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conscious decision to act the signal
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then goes back to an affector like the
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muscle in your arm via relay and motor
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neurons so that you move your arm a
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reflex is when the signal bypasses the
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brain and goes straight through the
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spine to the affector this is a reflex
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arc this of course is much faster than a
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con decision glands can also be
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effective which produce specific
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chemicals your body needs depending on
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the situation for example your salivary
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glands in your mouth making saliva when
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you eat food you can investigate into
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reaction Times by holding the bottom of
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a ruler between a person's finger and
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thumb and drop it without warning then
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you measure the distance it falls before
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they catch it do this multiple times and
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take a mean average not too many times
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though as their nervous systems will
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start to get a bit better at reacting to
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this you can introduce an independent
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variable like a stimulant for example
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coffee or a sugary drink or a depressant
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which will have the opposite effect
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although I can't think of any ones that
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are legal for you at the minute to see
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how they decrease or increase Reaction
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Time respectively you could calculate
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the reaction time from the distance
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using suvat S = half a^2 but you'll
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never be expected to do that in this
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paper but it's something you could
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mention if you were asked a six marker
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on this there are three parts of the
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brain you need to know the cerebral
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cortex is responsible for higher level
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functions like memory speech and problem
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solving the arum is responsible for your
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motor skills movement balance and
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coordination the medulla onunga controls
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unconscious actions your body takes you
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don't think about them like your heart
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and breathing rates it's also what
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controls the release of adrenaline MRI
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scans magnetic resonance imaging are a
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way of seeing the activity in your brain
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safely if something goes wrong with your
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brain though it can be very difficult or
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impossible to treat without damaging
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important parts of it your eyes are the
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most mind-bogglingly designed cameras
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ever conceived of a modation is the ey's
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ability to change the shape of the lens
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in order to focus light that comes from
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objects that are different distances
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away on the retina to focus light that
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comes from objects that are far away the
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ciliary muscles relax and the suspensory
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ligaments tighten they're both connected
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to the lens this results in the lens
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becoming thin and that means that light
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is only refracted a little bit and that
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focuses the light on the retina to focus
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on near objects the opposite is true the
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ciliary muscles contract the suspensory
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ligaments slacken and the lens becomes
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fatter or thicker and so that means that
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it becomes more powerful actually so
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light is refracted more which means that
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the light coming from the object still
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converges meets focuses on the retina so
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you can see a clear image the pupil the
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hole in the iris can change size
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depending on the light intensity hitting
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the eye the cornea is the transparent
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outer layer where light enters the eye
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it has a slight lensing effect itself
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while the White surface that covers the
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rest is called the Scara the light is
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focused then on the retina the back of
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the eye which consists of Rod and Cone
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stells which respond to light rods can
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only detect light intensity so no color
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while there are three different types of
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cones which detect green blue or red
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wavelengths of light a mix of which will
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produce the colors we then perceive when
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the signal reaches our brain via the
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optic nerve myopia is the medical term
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for shortsightedness you can't focus on
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Far objects hyperopia is
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long-sightedness glasses or contact
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lenses are usually used to mitigate this
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by slightly converging or diverging the
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light before it enters the eye laser eye
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surgery aims to change the shape of the
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cornea to achieve the same effect in
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order to reproduce sexually gametes sex
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cells must be made this happens by
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meiosis for example in the testes to
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make sperm the chromosomes in a diploid
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cell that is 23 pairs for us are copied
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similar chromosomes then pair up and the
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genes are swapped between them the cell
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then divides to make two diploid cells
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which then divide again along with the
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chromosomes themselves to make make four
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haid cells ready to fuse with another
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gamt which in this case would be an egg
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this is one way that variation occurs in
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Offspring plants do this with pollen and
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egg cells but they can also reproduce
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asexually but as it doesn't evolve
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gametes the daughter cells will be
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genetically identical so a clone of the
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parent is made by mitosis an advantage
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of sexual reproduction is that variation
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occurs which can result in organisms
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becoming better suited to their
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environment more in this in a bit so
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more likely to survive an advantage for
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asexual is that only one paent is needed
00:12:29
so for example a plant on its Lonesome
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can still reproduce in order for the
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species to survive another thing that
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can do both is the parasite that causes
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malaria genome is the term given to all
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the genetic material in an organism this
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code is stored in DNA of course which is
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a two stranded polymer in a double helix
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shape a gene is a section of DNA that
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codes for a specific protein the Human
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Genome Project completed its initial
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goal in 2003 when scientists mapped out
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what every Gene is responsible for
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coding this is powerful because it can
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help us identify what genes cause
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diseases or inherited disorders genotype
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is the term given to what code is stored
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in your DNA specifically well phenotype
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is how that code is expressed in your
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characteristics what proteins are made
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it affects your physiology for triple
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you need to know that the monomers
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between the two strands are called
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nucleotides and they're made from a
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sugar and phosphate group of which there
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are four types A T C and G G you don't
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need to know what the names are but a
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and t always match to each other in the
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sequence as do C and G every three of
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these bases we can call them are a code
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for an amino acid the sequence is copied
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by mRNA this copy is then taken out of
00:13:45
the nucleus to a ribosome in the cell
00:13:47
where amino acids are connected in the
00:13:50
order needed which makes a protein the
00:13:52
shape of which affects His function they
00:13:54
need to be folded as well first harmful
00:13:56
mutations can change a gene so much that
00:13:59
it results in a protein being
00:14:00
synthesized that doesn't do the job it's
00:14:02
supposed to we now know that some DNA
00:14:04
however doesn't directly code for
00:14:06
proteins but it influences how other
00:14:08
genes are expressed this is the realm of
00:14:10
epigenetics and it's changing the way
00:14:12
that we view DNA quite drastically back
00:14:15
to double some characteristics are
00:14:17
controlled by just one gene like color
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blindness these different types of the
00:14:21
same gene are called alals usually
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characteristics are dependent on two or
00:14:25
more genes though and them interacting
00:14:28
dominant Al are those that result in a
00:14:30
characteristic being expressed even if
00:14:32
there is another alil present a
00:14:34
recessive alil for example if you have
00:14:36
the Al's Big B little B for eye color
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Big B being brown little B being blue
00:14:42
you will have brown eyes it's only when
00:14:44
there's no dominant alal in this case
00:14:46
that the recessive alil is expressed so
00:14:49
me having blue eyes I must have the gene
00:14:52
little B little B Big B Big B or little
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B little B are called homozygous as they
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only have one type of alal where whereas
00:14:59
Big B little B is what we call
00:15:00
heterozygous we can use a punet square
00:15:03
to predict the probability of a certain
00:15:05
phenotype my parents have brown eyes but
00:15:07
they both have heterozygous alals for
00:15:10
eye color there are three different
00:15:12
outcomes of these combining with a 25%
00:15:15
chance of making me that's little be
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little be so I'm not so much one in a
00:15:19
million more one in four my sister has
00:15:21
brown eyes but her son has blue eyes so
00:15:23
she must be Big B little B eye color is
00:15:26
by The Bu but sums can result in
00:15:29
disorders being inherited for example
00:15:31
polya extra fingers or toes which is
00:15:34
caused by a dominant alil or cystic
00:15:36
vibrosis which is caused by a recessive
00:15:39
alal even if two parents don't have
00:15:41
cystic fibrosis they could still be
00:15:42
carrying the recessive alil so their
00:15:45
child could have the disorder human DNA
00:15:47
is contain in 23 pairs of chromosomes
00:15:49
but only one pair determines sex if you
00:15:52
have XX chromosomes you are female XY
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you're male the expression of these
00:15:56
genes affects every cell in your body
00:15:59
every aspect of your physiology we can
00:16:01
also make a punet square for these as
00:16:03
you can see there's a 50/50 chance of a
00:16:05
child being male or female variation is
00:16:07
a result of the genes inherited from an
00:16:09
organism's parents and also
00:16:11
environmental factors Charles Darwin's
00:16:13
theory of evolution states that random
00:16:15
variation in Offspring will result in
00:16:17
some being better suited to their
00:16:18
environment than others and so are more
00:16:20
likely to survive and reproduce but like
00:16:22
we've seen we know that our DNA is able
00:16:23
to respond to the environment in order
00:16:25
to turn genes on and off depending on
00:16:27
whether they're needed or not for
00:16:29
example there were some blind
00:16:30
translucent skin mackerel that were
00:16:31
found in a dark cave when they were bred
00:16:33
with normal mackerel in sunlight they
00:16:35
regained fully working eyes and opaque
00:16:37
skin within a few Generations Jean
00:16:39
Baptist Lamar's Theory asserted that
00:16:41
adaptation of variation is Guided by DNA
00:16:44
in response to a changing environment
00:16:46
this was scoffed at but we now know that
00:16:48
there is some truth to this thanks to
00:16:50
the discoveries made in epigenetics
00:16:53
bacterial resistance is largely
00:16:54
considered to be evidence of darwinian
00:16:56
evolution bacteria divid mutations occur
00:16:59
and inevitably a bacterium with an
00:17:01
increased resistance to antibiotics will
00:17:03
be produced that's why we only want to
00:17:05
use them when absolutely necessary it
00:17:07
also means you have to complete the
00:17:08
whole course of antibiotics if you don't
00:17:11
weaker bacteria will have been killed
00:17:12
off but more resistant ones will still
00:17:14
be there and then they'll reproduce and
00:17:17
make you even more ill if organisms are
00:17:19
able to produce fertile offspring we say
00:17:21
they're of the same species tigers and
00:17:23
lions have been known to make lier
00:17:25
Offspring but as they're infertile we
00:17:27
don't consider and lines to be the same
00:17:29
species we can selectively breed living
00:17:32
things with desired characteristics to
00:17:34
enhance these for example breeding dogs
00:17:36
to produ breeds like labrador's
00:17:38
colleagues and if you're into
00:17:40
undesirable characteristics pugs too
00:17:42
just for triple Johan Mendel was one of
00:17:44
the first people to assert that
00:17:45
characteristics were determined by units
00:17:48
that are passed onto Offspring due to
00:17:50
the discovery of genes and chromosomes
00:17:51
he was proven largely correct
00:17:54
advancements in biology over the last
00:17:56
few decades mean that we can also
00:17:58
genetically modify organisms if we don't
00:18:00
want to wait for selective breeding to
00:18:01
do the job or when it can't actually
00:18:03
achieve what we want it to for good or
00:18:05
ill for example scientists have
00:18:07
genetically modified bacteria to produce
00:18:09
insulin which can be harvested and used
00:18:11
to treat people with diabetes
00:18:13
genetically modifying crops is one way
00:18:15
of boosting their yields or nutritional
00:18:18
value for example golden rice has a gene
00:18:20
inserted into it that produces vitamin A
00:18:23
it was developed to combat diets in
00:18:25
certain areas that were lacking in this
00:18:27
other GM crops have been modified to be
00:18:29
more resistant to diseases for example
00:18:32
the process of genetic engineering goes
00:18:34
as follows a gene is chemically cut from
00:18:36
the organism that has the desired
00:18:38
characteristic this is done using
00:18:40
enzymes for example the gene from a
00:18:42
jellyfish that causes it to glow in the
00:18:44
dark this is then inserted into a vector
00:18:47
like a bacteria plasmid or virus that in
00:18:50
turn inserts the gene into another
00:18:52
organism say a bunny rabbit but it must
00:18:54
be done in the early stage of its
00:18:56
development say just after the Y has
00:18:58
been fertilized as this is the only way
00:19:00
you can be sure that the gene will be
00:19:02
present in every cell of the bunny as it
00:19:04
grows by the way I didn't make up this
00:19:06
example this has actually been done
00:19:09
fossils are the remains of organisms
00:19:11
that died a very long time ago the
00:19:12
classic fossils we think about are the
00:19:14
bones that we dig up but they're not
00:19:16
strictly speaking bones anymore in fact
00:19:18
minerals have replaced the organic
00:19:20
material to effectively leave Rock in
00:19:23
exactly the same shape as the bone
00:19:26
sometimes there can still be organic
00:19:27
tissue left behind if the conditions for
00:19:29
Decay are not present Footprints left in
00:19:32
mud that have hardened over time for
00:19:34
example are also considered fossils as
00:19:36
well as any other trace of an organism
00:19:39
it doesn't have to be the organism
00:19:40
itself CBD cardiovascular disease is an
00:19:44
example of a non-communicable disease as
00:19:46
the cause of it comes from inside your
00:19:48
body other examples of such diseases
00:19:51
include autoimmune conditions like
00:19:53
allergic reactions and cancer a
00:19:55
communicable disease must be caused by a
00:19:57
pathogen that enters your body that will
00:19:59
cause a viral bacterial or fungal
00:20:02
infection again more on these in a bit
00:20:04
back to non-communicable diseases
00:20:06
obesity and too much sugar can cause
00:20:08
type 2 diabetes a bad diet smoking and
00:20:11
lack of exercise can affect the risk of
00:20:12
heart disease alcohol can cause liver
00:20:15
diseases smoking lung disease or cancer
00:20:18
a carcinogen is the name given to
00:20:20
anything that increases the risk of
00:20:21
cancer for example ionizing radiation
00:20:24
cancer is a result of damaged cells
00:20:26
dividing uncontrollably lead into tumors
00:20:29
benign cancers don't spread through the
00:20:31
body and they're relatively easy to
00:20:32
treat however malignant cancers are when
00:20:35
these cancerous cells spread through
00:20:37
your body much worse BMI stands for body
00:20:40
mass index it's an indication of whether
00:20:43
or not somebody has a healthy weight or
00:20:45
not relative to their height the
00:20:47
equation is this BMI is equal to weight
00:20:49
well Mass we know don't we divided by
00:20:52
height squared and whatever number you
00:20:53
have will put you into certain bands
00:20:56
will determine whether or not you're a
00:20:57
healthy BMI overweight obese Etc as
00:21:01
mentioned just now communicable diseases
00:21:03
are caused by pathogens that can be
00:21:05
viruses bacteria fungi or protests these
00:21:08
are single celled parasites they all
00:21:10
reproduce in your body and cause damage
00:21:12
but viruses can't reproduce by
00:21:14
themselves a virus is in fact just a
00:21:16
protein casing that surrounds genetic
00:21:18
code that it injects into a cell which
00:21:21
causes the cell to produce more copies
00:21:23
of the virus the cell explodes and the
00:21:26
virus goes on to infect more cells
00:21:28
creepy isn't it HIV is an STD or STI
00:21:31
sexually transmitted disease or
00:21:33
infection that compromises your immune
00:21:35
system this is also called aids for
00:21:37
short it can also be spread by people
00:21:39
sharing needles bacteria on the other
00:21:42
hand release toxins that damage your
00:21:44
body cells fungi do something similar
00:21:47
like athletes foot while protus do all
00:21:49
sorts of different things for example
00:21:50
malaria is caused by a proest that
00:21:52
burrows into red blood cells to multiply
00:21:55
then burst out destroying the red blood
00:21:56
cell in the process it's spread by
00:21:58
mosquitoes so we say mosquitoes are the
00:22:01
vector for the disease our bodies are
00:22:03
excellent at protecting us from these
00:22:05
pathogens though thank goodness skin is
00:22:07
the first barrier to them entering and
00:22:08
if they do enter your nose and trachea
00:22:11
they can be trapped by mucus acid and
00:22:13
enzymes in your digestive system will
00:22:15
destroy them too if they still manage to
00:22:17
enter the bloodstream though white blood
00:22:19
cells are ready to combat them one type
00:22:20
of these are called lymphocytes they
00:22:22
produce antitoxins to neutralize the
00:22:24
poisons pathogens produce and also they
00:22:27
make antibodies which stick to the
00:22:29
antigen on a pathogen and this stops
00:22:31
them from being able to infect more
00:22:32
cells and it makes them Clump together
00:22:35
fago sites are then able to ingest them
00:22:37
and Destroy them an antigen on a
00:22:39
pathogen will have a specific shape so
00:22:41
that means only an antibody that fits it
00:22:43
will neutralize it if pathogens are
00:22:46
unknown to the immune system lymphocytes
00:22:48
will start making all different shapes
00:22:50
until one fits miraculously your immune
00:22:53
system will then store a copy of this
00:22:54
antibody next to a copy of the antigen
00:22:57
so it's ready to stop it from causing an
00:22:59
infection next time you're exposed to it
00:23:01
you now have immunity a vaccine is a
00:23:04
dead or inert version of a pathogen
00:23:06
usually a virus that exposes your immune
00:23:08
system to the pathogen so it can produce
00:23:10
the antibody without it infecting you
00:23:12
for example the flu vaccine you're
00:23:13
injected with the virus that has been
00:23:15
irradiated so the DNA has been damaged
00:23:18
inside so it can't do the job
00:23:20
incidentally the co jab however was
00:23:22
intended to work differently instead
00:23:23
you're injected with the DNA technically
00:23:26
mRNA needed to trick your cells into
00:23:28
synthesizing part of the virus including
00:23:31
the antigen it was the first widely used
00:23:33
jab that used this mRNA technology just
00:23:36
for triple bacteria multiply by binary
00:23:39
fision so the number doubles every say
00:23:41
10 minutes so if we started with one
00:23:43
bacterium after an hour we'd have 2 to
00:23:46
the^ of 6 that's 64 after 6 hours that's
00:23:49
36 lots of 10 minutes so in theory we'd
00:23:52
have 2 to ^ of 36 that's in standard
00:23:55
form 6.87 * 10 10 we can do a itical on
00:23:58
this by producing a culture on agar in a
00:24:01
Petra dish using aseptic technique that
00:24:03
is making sure nothing else contaminates
00:24:05
the culture we lift the lid of the dish
00:24:07
towards a flame which causes other
00:24:09
microbes in the air to move away and
00:24:10
upwards from the dish and it destroys
00:24:12
them too using sterilized equipment we
00:24:14
can either put a drop of bacteria
00:24:16
culture in the middle or spread it all
00:24:17
around and put spots of different
00:24:19
antibiotics on top instead we put a few
00:24:21
bits of tape around the dish to hold the
00:24:23
lid on but not all the way around
00:24:25
otherwise air will not get in and the
00:24:26
bacteria will respire an aerobically we
00:24:29
then incubate it at 25° once the culture
00:24:32
has grown we can either calculate the
00:24:33
size of the culture from an initial drop
00:24:35
or the area in which bacteria did not
00:24:37
grow or were killed by an antibiotic to
00:24:39
then compare with others in both cases
00:24:41
we use Pi r^ squ or pi d^2 over 4 to
00:24:44
calculate the area of the circles
00:24:46
antibiotics kill bacteria they don't
00:24:49
kill viruses penicillin was the first
00:24:51
one there are good bacteria in our body
00:24:53
so antibiotics are designed to be as
00:24:56
specific as possible because you don't
00:24:57
want to damage those or your body cells
00:24:59
either problem is as bacteria mutate
00:25:02
they can become resistant to them so the
00:25:04
more you use them the less effective
00:25:05
they become drugs used to be extracted
00:25:08
from plants and other organisms for
00:25:10
example aspirin comes from willow trees
00:25:12
penicillin from a mold now synthesizing
00:25:14
drugs is one of the biggest industries
00:25:16
on the planet they have to be trial to
00:25:18
see how effective they are and to check
00:25:20
for side effects first we do lab trials
00:25:22
on Cell tissue than trials on animals
00:25:25
next human trials we give the drug to a
00:25:27
group of people but we also give a
00:25:29
placebo to a control group without
00:25:31
telling them say a pill that's just
00:25:33
sugar not the actual drug this is what
00:25:35
we call a blind trial because the test
00:25:38
subjects don't know what they're taking
00:25:40
a double blind trial is when even those
00:25:42
analyzing the results from the tests
00:25:44
aren't aware of which group is which and
00:25:47
that's to eliminate any bias just for
00:25:49
triple this is a crazy one monoclonal
00:25:52
antibodies they're made from clones of a
00:25:54
cell which is able to produce a specific
00:25:56
antibody to combat a disease
00:25:58
this is achieved by combining
00:26:00
lymphocytes from me tumor cells and this
00:26:02
makes a hybridoma cell this is then
00:26:05
cloned to produce a lot of antibodies
00:26:07
ready to treat a patient these
00:26:09
monoclonal antibodies can also be used
00:26:10
for medical diagnosis pathogen detection
00:26:13
in a lab or even just identifying
00:26:15
molecules in tissue by binding them to a
00:26:18
dye so they glow when grouped together
00:26:21
because they'll be designed to bind to a
00:26:23
specific molecule the downside to these
00:26:25
is that the side effects are turning out
00:26:26
to be worse than scientists expected so
00:26:29
I hope you found that helpful leave a
00:26:30
like if you did and pop any questions or
00:26:32
comments below and hey after you've done
00:26:34
the exam come back here and tell us all
00:26:35
how you found it we'd love to know click
00:26:37
on a card to go to the playlist for all
00:26:39
six papers I'll see you in the next
00:26:41
video best of luck
