How to Read a Codon Chart

00:07:49
https://www.youtube.com/watch?v=LsEYgwuP6ko

摘要

TLDRThe video explains how to read codon charts, focusing on the relationship between mRNA codons and the amino acids they code for. It covers the basics of codons, the importance of using the correct codon chart, and common mistakes to avoid. The video also provides examples using both rectangular and circular codon charts, demonstrating how to find the corresponding amino acids for given codons. It emphasizes the significance of practice in mastering the use of codon charts.

心得

  • 🧬 Codons are groups of 3 RNA bases that code for amino acids.
  • 📊 Use the mRNA codon, not the tRNA anticodon, when reading codon charts.
  • 🔍 Rectangular and circular codon charts are common representations.
  • 🚀 AUG is a start codon that codes for methionine.
  • 🛑 UAA is a stop codon that signals the end of protein synthesis.
  • ⚠️ Common pitfalls include using the wrong codon and not practicing enough.
  • 💡 Practice is essential for mastering codon charts.
  • 🔄 Codons AAA and AAG code for lysine.
  • 🔢 Six codons code for serine: UCU, UCC, UCA, UCG, AGU, AGC.

时间轴

  • 00:00:00 - 00:07:49

    This video provides a detailed introduction to reading a codon chart, assuming prior knowledge from previous videos on DNA vs RNA and Protein Synthesis. It explains the structure of codons, the transition from DNA to mRNA, and the significance of codons in determining amino acid sequences which contribute to human and other organism traits. It discusses the two types of codon charts: rectangular and circular, and illustrates how to use them with examples. Moving through the codon examples, the importance of using the correct mRNA codon and understanding potential pitfalls in reading codon charts is emphasized. Practice is encouraged, with activities to identify codons for specific amino acids.

思维导图

视频问答

  • What is a codon?

    A codon is a sequence of three RNA bases that codes for a specific amino acid.

  • How do you read a codon chart?

    To read a codon chart, identify the first, second, and third bases of the codon and find their intersection in the chart.

  • What is the significance of understanding codons?

    Understanding codons helps in comprehending how amino acids are coded, which is essential for understanding human traits and biological functions.

  • What are the common types of codon charts?

    The most common types of codon charts are rectangular and circular charts.

  • What is a start codon?

    A start codon, such as AUG, signals the beginning of protein synthesis and codes for the amino acid methionine.

  • What are stop codons?

    Stop codons signal the end of protein synthesis and do not code for any amino acid.

  • What are some common pitfalls when reading codon charts?

    Common pitfalls include not using the mRNA codon, getting stuck on the rectangular chart, and not practicing enough.

  • How many codons code for lysine?

    The two codons that code for lysine are AAA and AAG.

  • Which codons code for serine?

    The mRNA codons that code for serine are UCU, UCC, UCA, UCG, AGU, and AGC.

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  • 00:00:00
    Captions are on! Click CC at bottom right to turn off!
  • 00:00:04
    Ah, codons.
  • 00:00:05
    If you chose to watch this short video, you are perhaps searching for a little additional
  • 00:00:10
    help to read a codon chart.
  • 00:00:12
    And you’ve come to the right place.
  • 00:00:13
    We’re going to assume you already have the background from our DNA versus RNA video and
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    our Protein Synthesis video.
  • 00:00:20
    If not…you might want to check those out first or otherwise jumping right into this
  • 00:00:24
    isn’t going to make much sense.
  • 00:00:27
    Oh, and in addition, we have a video companion handout to this video which can be helpful.
  • 00:00:32
    Expand this video’s details for the link as you may want to download it first.
  • 00:00:36
    So if you had this DNA template strand here, you’d have this mRNA built.
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    I know this because of how RNA bases pairs with DNA bases.
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    Notice how these mRNA bases are written here in groups of 3?
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    Each is a codon.
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    Bases are read in threes so a codon is how these bases will be “read.”
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    In this example, there are a total of 5 codons.
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    15 individual RNA bases.
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    By reading a codon chart, you can determine the amino acids that will be brought in by
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    the tRNAs.
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    You can determine the sequence of amino acids that make up a protein.
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    And if you’re wondering why this matters---understanding how amino acids are coded for helps us understand
  • 00:01:20
    human traits and how changes in amino acids have the potential to alter those traits.
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    Not just for humans either but all living organisms!
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    The codons and their corresponding amino acids have been discovered by scientists.
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    There are many ways you can represent the information in a chart.
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    The most common ways are the rectangular codon chart and the circular codon chart.
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    Let’s get started.
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    The first codon---remember codons have three bases and codons are on the mRNA---is AUG.
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    That means the tRNA anticodon will be UAC, and we know that because of the base pairing
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    rules.
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    Now, which amino acid will that tRNA carry?
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    Time to use the codon chart!
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    We’ll use a rectangular one, and remember, it’s the mRNA codon that we look at.
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    Not the tRNA anticodon.
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    So notice on the left side of the chart, it is for the first base.
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    The top is for the second base.
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    And the right side is for the third base.
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    We’re looking at the codon AUG.
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    We go in order.
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    First base letter: A. We isolate this row here and only this row.
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    Second base letter: U.
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    We isolate this column here and only this column.
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    We’ve narrowed it down to this area here where they intersect.
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    Third base letter: G.
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    Here!
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    The codon AUG codes for the amino acid methionine.
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    Fun fact: methionine is commonly the starting amino acid for many polypeptide chains as
  • 00:02:54
    AUG is a start codon.
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    Next codon is CCA.
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    That means the anticodon for the tRNA will be GGU.
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    Now, what amino acid will that tRNA carry?
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    Time to use the codon chart!
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    This time, we’re going to ask you to pause the video while you try to determine which
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    amino acid this tRNA would be carrying.
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    Again, don’t forget to use the mRNA codon.
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    Not the tRNA anticodon.
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    So, in slow motion, let’s go through this chart.
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    First base letter: C. That narrows down this row.
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    Second letter C. That narrows down this column, and therefore this area here where they meet.
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    Third letter A. The amino acid proline!
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    Aright, the third codon.
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    GUC.
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    This time, we need you to determine the tRNA anticodon, and also, the amino acid that tRNA
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    would be carrying.
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    Pause the video to determine those.
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    The anticodon, based on the base pairing rules, would be CAG.
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    But we use the mRNA codon for this codon chart, and when you used it---showing this in slow
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    motion here--- you should have gotten the amino acid valine.
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    Now, with those three codons, we used a rectangular codon chart.
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    We mentioned that there are other ways to represent the information, and the circular
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    chart is common to find as well.
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    The circular codon chart typically works by starting on the inside and moving outward.
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    So, this fourth codon we have here is UUC.
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    That means the tRNA anticodon would be AAG, but again we’re going to use the mRNA codon
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    in the chart.
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    So, we start with the center.
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    First letter U, which isolates to this area.
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    Then we move out one to the second letter which isolates further: U.
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    Finally, we move one more time to the C.
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    This is the amino acid phenylalanine.
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    Your turn now to use the circular codon chart with this last codon.
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    UAA.
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    What does the mRNA codon UAA stand for?
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    [PAUSE] In slow motion, you can see that we get “stop.”
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    This does not code for an amino acid; instead, it is generally at the end of a sequence for
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    a polypeptide.
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    And, well, this signals the end of reading the codon chart…for this little chain of
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    amino acids anyways.
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    In reality, polypeptides tend to have many more amino acids than this and proteins tend
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    to be made of one or more of these polypeptide chains.
  • 00:05:34
    We hope this was helpful, but before we go, we want to mention just a few pitfalls with
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    reading codon charts.
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    Pitfall #1: Not using the mRNA codon.
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    Unless it specifies otherwise, the mRNA codon is what you want to use for the codon chart.
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    Some students will accidentally try to use the tRNA anticodon.
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    Some students will try to use the original DNA template.
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    Now while there are charts that exist for the tRNA anticodon or DNA, unless it specifically
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    says otherwise, you should assume it’s for the mRNA codon.
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    Pitfall #2: Getting stuck on the standard rectangular chart.
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    Pinky has noticed students tend to have more challenges with the rectangular one.
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    We suggest going slowly, and even using a highlighter if you’re able to---that way
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    you can see where the first base isolates the row, the second base isolates the column,
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    and third base finishes in isolating the amino acid.
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    Remember to go carefully in order.
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    Pitfall #3: Not practicing.
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    You got to practice; that’s why this video has a video companion.
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    So let’s do some more practice by going backwards!
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    So using this circular codon chart, can you tell me the two codons that code for lysine?
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    Go ahead and pause the video for a moment.
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    So, using this circular codon chart, we can see the codons AAA and AAG code for lysine.
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    Let’s use this rectangular codon chart here now.
  • 00:07:05
    Which six mRNA codons could code for the amino acid serine?
  • 00:07:13
    The mRNA codons that code for serine are UCU, UCC, UCA, UCG, AGU, and AGC.
  • 00:07:22
    Phew that’s a lot of codons!
  • 00:07:25
    Well, that’s it for the Amoeba Sisters, and we remind you to stay curious!
标签
  • codons
  • mRNA
  • amino acids
  • codon chart
  • protein synthesis
  • DNA
  • RNA
  • genetics
  • biological functions
  • Amoeba Sisters