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Multiple Choice
Which of the following sequences of nucleotides are possible in the template strand of DNA that would code for the polypeptide sequence Phe–Leu–Ile–Val?
A
5′–TTG–CTA–CAG–TAG–3′.
B
5′–AUG–CTG–CAG–TAT–3′.
C
3′–AAA–AAT–ATA–ACA–5′.
D
3′–AAA–GAA–TAA–CAA–5′.
Verified step by step guidance
1
Understand that the template strand of DNA is complementary to the mRNA strand, which is used during translation to form a polypeptide chain.
Identify the mRNA codons that code for the amino acids Phe, Leu, Ile, and Val using the codon chart. Phe is coded by UUU or UUC, Leu by UUA, UUG, CUU, CUC, CUA, or CUG, Ile by AUU, AUC, or AUA, and Val by GUU, GUC, GUA, or GUG.
Convert the mRNA codons to the corresponding DNA template strand. Remember that in DNA, adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). Uracil (U) in RNA is replaced by thymine (T) in DNA.
For the polypeptide sequence Phe–Leu–Ile–Val, the mRNA sequence could be UUU–UUA–AUU–GUU. Convert this to the DNA template strand: AAA–AAT–TAA–CAA.
Verify the sequence by checking each codon conversion: UUU (Phe) to AAA, UUA (Leu) to AAT, AUU (Ile) to TAA, and GUU (Val) to CAA. This matches the correct answer provided.