Question

the chart shows how each mrna codon corresponds to an amino acid.
select all the dna codons that code for aspartic acid.
a. cag
b. cta
c. ctg
d. gac
e. gau

Explanation:

Step1: Understand DNA - mRNA relationship

DNA is transcribed to mRNA. The mRNA codon for aspartic acid is GAU or GAC. Using the base - pairing rules (A - U, T - A, C - G, G - C for DNA to mRNA transcription), if mRNA is GAU, then the DNA codon is CTA (since G in mRNA pairs with C in DNA, A in mRNA pairs with T in DNA, U in mRNA pairs with A in DNA). If mRNA is GAC, then the DNA codon is CTG (G in mRNA pairs with C in DNA, A in mRNA pairs with T in DNA, C in mRNA pairs with G in DNA).

Step2: Check each option

• Option A: CAG. Transcribing CAG to mRNA gives GUC (C - G, A - U, G - C), which does not code for aspartic acid.
• Option B: CTA. Transcribing CTA to mRNA gives GAU (C - G, T - A, A - U), which codes for aspartic acid.
• Option C: CTG. Transcribing CTG to mRNA gives GAC (C - G, T - A, G - C), which codes for aspartic acid.
• Option D: GAC. Transcribing GAC to mRNA gives CUG (G - C, A - U, C - G), which does not code for aspartic acid.
• Option E: GAU. Transcribing GAU to mRNA gives CTA (G - C, A - U, U - A), but GAU is an mRNA codon, not a DNA codon.

Answer:

B. CTA, C. CTG