The sequence of a portion of a gene is presented below: 5-AGCAATGCATGCATCGTTATGG

Question

The sequence of a portion of a gene is presented below:

5-AGCAATGCATGCATCGTTATGG-3 sense strand

3-TCGTTACGTACGTAGCAATACC-5 antisense strand

Assuming that transcription starts with the first T in the template strand of the DNA, and continues to the end, what would be the sequence of the transcribed mRNA?

5-AGCAAUGCAUGCAUCGUUAUGG-3

Identify the initiation codon in this mRNA.

5-AGCAAUGCAUGCAUCGUUAUGG-3

(c) Would there be an effect on translation of changing the first C in the template strand to a G? If so, what effect? No, because a it is before the start codon

(d) Would there be an effect on translation of changing the third G in the template strand to a T? If so, what effect? Yes, because GCA codes for Alanine changing the codon to TCA

(e) Would there be an effect on translation of changing the last A in the template strand to a C? If so, what effect?

(f) Would there be an effect on translation if pyrrolysine were present?

Explanation / Answer

Sequence of the transcribed mRNA is 5-AGCAAUGCAUGCAUCGUUAUGG-3

Initiation codon in this mRNA is AUG

(c) No. The first C is in the 5-untranslated region (5-UTR) of the mRNA. Changing it to a G would not have a direct effect on the translation; i.e., the amino acid sequence would be the same.

(d) Yes. This would change GCA which codes for alanine, to GAA which codes for glutamine.

(e) Yes. This would change UGG which codes for tryptophan, to UAG which is a stop codon.

(f) Yes. The UAG codon in some instances can trigger incorporation of pyrrolysine (the 22nd amino acid) rather than termination.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.