Final answer:
After transcription of the template DNA strand into RNA and translation into amino acids, the polypeptide sequence encoded by the given gene is Met-Ala-Ser-Cys-Lys-Gly. This matches option (b).
Step-by-step explanation:
The student's DNA sequence needs to be transcribed into mRNA and then translated into a polypeptide chain. Transcription involves rewriting the DNA code into RNA, where the DNA base 'A' pairs with 'U' in RNA, 'T' pairs with 'A', 'C' pairs with 'G', and 'G' pairs with 'C'. The DNA sequence given is 5'…CCCAGCCTAGCCTTTGCAAGAGGCCATATCGAC…3', but we should use the template strand (3'…GGGTCGGATCGGAAACGTTCTCCGGTATAGCTG…5') to transcribe into mRNA because transcription uses the template strand of DNA.
Transcription will yield the following mRNA sequence: 5'…CCAGUCCUAGCCUUUGCAAGAGGCCAUAUCGAC…3' (removing the initial 'GGG' since we're told to include only the sequence with start and stop codons). The start codon is AUG, so we look for a sequence that starts with AUG after transcription. This gives us the mRNA sequence AUG (start codon) CAAGAG (Gln, Glu) GCCAUA (Ala, Ile) U (stop codon).
Finally, we translate this mRNA sequence into a polypeptide sequence. According to the genetic code, we get:
- Met (start codon AUG)
- Ala (GCU)
- Ser (UCG)
- Cys (UGC)
- Lys (AAA)
- Gly (GGG)
Therefore, the correct polypeptide sequence encoded by this gene is Met-Ala-Ser-Cys-Lys-Gly, which corresponds to option (b).