To determine the sequence of nucleotides in the template strand of DNA that could code for the polypeptide sequence Val-His-Thr, let's go through the steps to find the DNA sequence corresponding to the given mRNA codons.
1. Identify the mRNA Codons for the Polypeptide Sequence:
- Val (Valine) -> mRNA codon: GUA
- His (Histidine) -> mRNA codon: CAU
- Thr (Threonine) -> mRNA codon: ACC
2. Understand the Relationship Between mRNA and DNA:
- mRNA codons are complementary to the DNA template strand.
- mRNA codons are read in the 5' to 3' direction, whereas the template strand of DNA is read in the 3' to 5' direction.
3. Determine the Complementary DNA Template Strand:
- mRNA codon GUA (Val) binds to: DNA template strand CAT (G is complementary to C, U is complementary to A, A is complementary to T)
- mRNA codon CAU (His) binds to: DNA template strand GTA (C is complementary to G, A is complementary to T, U is complementary to A)
- mRNA codon ACC (Thr) binds to: DNA template strand TGG (A is complementary to T, C is complementary to G, C is complementary to G)
4. Combine the DNA Sequence:
- From the mRNA sequence GUA-CAU-ACC, the template DNA sequence is:
- GUA -> CAT
- CAU -> GTA
- ACC -> TGG
Therefore, the sequence of nucleotides in the template strand of DNA that could code for the polypeptide sequence Val-His-Thr is:
CAT-GTA-TGG
Hence, the correct option is:
CAT-GTA-TGG
