Question

use complementary base pairing and this codon chart to answer the question.
write the amino acid using its three - letter abbreviation. write stop for a stop codon.
dna sequence: cag
mrna codon:
irma anticodon:
amino acid:

Explanation:

Step1: Find mRNA codon from DNA

DNA sequence is CAG. In transcription, DNA's C pairs with G, A with U, G with C? Wait, no: DNA to mRNA is complementary base pairing, with T (but DNA here has C, A, G; mRNA uses U instead of T). So DNA C (cytosine) pairs with G? No, wait: DNA template strand to mRNA: A-U, T-A, C-G, G-C. Wait, the DNA sequence given is CAG (coding strand? Or template? Wait, usually, mRNA is transcribed from DNA template, but if the DNA is the coding strand (same as mRNA except T instead of U), but here the DNA is CAG, so mRNA codon would be CAG's complement? Wait no, maybe the DNA is the coding strand, so mRNA is same as DNA but T→U. Wait, no, the DNA sequence here is CAG, so mRNA codon: C (DNA) → G? No, I think I got it wrong. Wait, complementary base pairing: DNA (template) to mRNA: A→U, T→A, C→G, G→C. But if the DNA given is the coding strand (non-template), then mRNA is same as coding strand but T→U. But the problem says "DNA sequence CAG", so let's assume that the DNA is the template? Wait, no, maybe the DNA is the coding strand, so mRNA codon is CAG (but with U instead of T? No, CAG has no T. Wait, DNA has C, A, G. So mRNA codon: C (DNA) pairs with G? No, I'm confused. Wait, the standard is: DNA template strand: 3'-...-5', mRNA is 5'-...-3', with A-U, T-A, C-G, G-C. So if DNA is CAG (let's say 5'-CAG-3' coding strand), then mRNA is CAG (but with U? No, CAG has C, A, G. So mRNA codon would be CAG? Wait, no, maybe the DNA is the template strand: 3'-CAG-5', then mRNA is 5'-GUC-3'? Wait, no, 3'-CAG-5' (template) would transcribe to 5'-GUC-3' (mRNA). Wait, but the problem's codon chart is for mRNA. So let's check the codon chart. The codon chart has U, C, A, G in the center. Wait, maybe I made a mistake. Wait, the DNA sequence is CAG, so to get mRNA, we do complementary base pairing: C (DNA) → G? No, A (DNA) → U, T (DNA) → A, C (DNA) → G, G (DNA) → C. Wait, DNA is CAG: C, A, G. So mRNA codon: C (DNA) → G? No, that can't be. Wait, maybe the DNA is the coding strand, so mRNA is CAG (since there's no T, so mRNA is CAG? But CAG has C, A, G. Wait, the codon chart is for mRNA, so the mRNA codon is what we use to look up the amino acid. Wait, maybe the DNA sequence CAG is the template, so mRNA is GUC? Wait, no, let's take an example. If DNA is CAG (template: 3'-CAG-5'), then mRNA is 5'-GUC-3' (since C (3' end) pairs with G (5' mRNA), A pairs with U, G pairs with C). Wait, but the codon chart has U, C, A, G. Let's look at the codon chart. The center of the chart has U, C, A, G (maybe the first base), then the next ring, then the outer. Wait, the codon chart is a wheel: first base (center), second (middle ring), third (outer ring). Wait, the center has U, C, A, G (maybe the first base of the codon). Wait, looking at the chart, the center is U, C, A, G (divided into four: U, C, A, G? Wait, the center has G, U, A, C? Wait, the center of the wheel: the four quadrants are G (red), U (purple), A (blue), C (yellow)? Wait, no, the center has G, U, A, C? Wait, the center of the wheel: the four main sections are G (red), U (purple), A (blue), C (yellow)? Wait, the center has "G", "U", "A", "C" in four quadrants? Wait, the center is divided into four: top red is G, right purple is U, bottom blue is A, left yellow is C? Wait, no, looking at the image: the center has "G" (red), "U" (purple), "A" (blue), "C" (yellow) in four quadrants. Then the next ring (middle) has letters: around the center, the middle ring has A, G, U, C? Wait, no, the middle ring (second layer) has A (blue), G (red), U (purple), C (yellow) in each quadrant? Wait, maybe the codon is read as first base (center), second base (middle ring), third base (outer ring). Wait, let's take an example. For example, if the codon is GUC: first base G (center, red), second base U (middle ring, purple), third base C (outer ring, yellow). Then the amino acid would be Valine (Val). Wait, but let's get back. The DNA sequence is CAG. Let's find mRNA codon. Let's assume that DNA is the template strand: DNA template is CAG (3'-CAG-5'), so mRNA is 5'-GUC-3' (since C (DNA) pairs with G (mRNA), A (DNA) pairs with U (mRNA), G (DNA) pairs with C (mRNA)). So mRNA codon is GUC. Now, let's use the codon chart. First base of mRNA codon: G (center, red quadrant). Second base: U (middle ring, purple quadrant). Third base: C (outer ring, yellow quadrant). Now, look at the chart: the outer ring has amino acids. Let's find the section for first base G, second base U, third base C. Wait, the first base is G (center, red), second base U (middle ring, purple), third base C (outer ring, yellow). Looking at the chart, the outer ring (amino acids) for G (first), U (second), C (third): let's see the positions. Wait, the outer ring has Valine (Val), arginine (Arg), serine (Ser), etc. Wait, when first base is G, second base U, third base C: let's check the chart. The center is G (red), middle ring (second base) U (purple), third base C (yellow). The corresponding amino acid: looking at the outer ring, the section for G (first), U (second), C (third) is Valine (Val)? Wait, no, maybe I messed up the mRNA codon. Wait, maybe the DNA sequence CAG is the coding strand, so mRNA is CAG (since DNA has C, A, G, so mRNA is CAG, with U instead of T, but CAG has no T, so mRNA is CAG? Wait, that can't be, because CAG in mRNA would be first base C, second A, third G. Let's check the chart for first base C (yellow, left), second base A (blue, bottom), third base G (red, top). Wait, first base C (yellow, center left), second base A (blue, middle ring), third base G (red, outer ring). Looking at the outer ring, that section is Glutamine (Gln)? Wait, the outer ring has "Glutamine (Gln)"? Wait, the left side of the chart: the outer ring has "Glutamine (Gln)"? Wait, the problem says "Write the amino acid using its three-letter abbreviation". Let's re-express:

If DNA is CAG, then mRNA codon: DNA (coding strand) → mRNA is CAG (since DNA has C, A, G; mRNA has C, A, G (no T, so same as DNA but T→U, but CAG has no T). Wait, that makes sense. So mRNA codon is CAG. Now, let's use the codon chart: first base C (yellow, center left), second base A (blue, middle ring), third base G (red, outer ring). Looking at the outer ring, the section for first base C, second A, third G: let's see the amino acids. The outer ring has "Glutamine (Gln)"? Wait, the left side of the chart: the outer ring has "Glutamine (Gln)"? Wait, the problem's chart: looking at the outer ring, the left side (first base C, second A, third G) – let's check the labels. The outer ring has labels like "Glutamine (Gln)", "Valine (Val)", "Arginine (Arg)", "Serine (Ser)", "Threonine (Thr)", "Asparagine (Asn)", "Lysine (Lys)", "Aspartic acid (Asp)", "Glutamic acid (Glu)", "Glycine (Gly)", "Alanine (Ala)", "Proline (Pro)", "Leucine (Leu)", "Isoleucine (Ile)", "Methionine (Met)", "Phenylalanine (Phe)", "Tyrosine (Tyr)", "STOP", "Cysteine (Cys)", "Tryptophan (Trp)", "Leucine (Leu)", "Proline (Pro)", etc. Wait, let's parse the chart:

- First base C (yellow, center left), second base A (blue, middle ring), third base G (red, outer ring): the corresponding amino acid is Glutamine (Gln)? Wait, no, let's check the standard codon table. The standard codon table: CAG is Glutamine (Gln). Yes! Because CAG in mRNA is the codon for Glutamine (Gln). So that's the amino acid.

Wait, let's confirm:

Standard codon table:

Codon CAG: Glutamine (Gln)

Yes, because:

- First base C

- Second base A

- Third base G

So CAG → Gln.

So the amino acid is Glutamine, three-letter abbreviation Gln.

Step2: Verify with the chart

Looking at the codon chart: first base C (yellow, center left), second base A (blue, middle ring), third base G (red, outer ring). The outer ring in that section should be Glutamine (Gln). So that's correct.

Answer:

Gln