To determine which sequence of nucleotides in the template strand of DNA could code for the polypeptide sequence Val-Asp-Ser, we follow these steps:
1. Identify the mRNA codons for each of the amino acids in the polypeptide sequence:
- Val (Valine)
- Asp (Aspartic acid)
- Ser (Serine)
2. Utilize the provided codon table to find the corresponding mRNA codons for each amino acid.
- For Valine (Val), the possible mRNA codons are:
[tex]\[
\text{GUU, GUC, GUA, GUG}
\][/tex]
- For Aspartic acid (Asp), the mRNA codons are:
[tex]\[
\text{GAU, GAC}
\][/tex]
- For Serine (Ser), the mRNA codons are:
[tex]\[
\text{UCU, UCC, UCA, UCG, AGU, AGC}
\][/tex]
3. Select one codon for each amino acid. From the given protein sequence, we choose:
[tex]\[
\text{GUU for Val, GAU for Asp, and AGC for Ser}
\][/tex]
Hence, the mRNA sequence is:
[tex]\[
\text{GUU-GAU-AGC}
\][/tex]
4. Convert this mRNA sequence to the corresponding DNA sequence. Remember, in DNA, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C). Therefore, we take the complementary DNA sequence.
The mRNA sequence:
[tex]\[
\text{GUU-GAU-AGC}
\][/tex]
The complementary DNA sequence (which is the template strand from which the mRNA would be transcribed) is:
[tex]\[
\text{CAA-CTA-TCG}
\][/tex]
5. Verifying the given options, we also have:
[tex]\[
\text{GTT-GAT-AGC}
\][/tex]
Since transcription involves creating a complementary mRNA sequence from the DNA template strand by pairing bases (A with T/U and C with G), converting back from mRNA to DNA:
- G from mRNA with C from DNA
- U from mRNA with A from DNA
- A from mRNA with T from DNA
Thus:
- GUU from mRNA corresponds with CAA from DNA template
- GAU from mRNA corresponds with CTA from DNA template
- AGC from mRNA corresponds with TCG from DNA template
So, the matching sequence of nucleotides in the template strand of DNA to code the polypeptide sequence Val-Asp-Ser is:
[tex]\[
\text{GTT-GAT-AGC}
\][/tex]
Therefore, the final sequence in the template strand of DNA that codes for the polypeptide sequence Val-Asp-Ser is:
[tex]\[
\text{GTT-GAT-AGC}
\][/tex]
