BIO-315 Class exercises October 2017 1) The sequence of nucleotides in an mRNA i

Question

BIO-315 Class exercises October 2017 1) The sequence of nucleotides in an mRNA is 5'-AUGACCCAUUGGUCUCGUUAG-3' a) Assuming that ribosomes could translate this mRNA, how many amino acids long would you expect the resulting polypeptide chain to be? b) Hydroxylamine is a mutagen that results in the replacement of an A-T base pair for a G c base pair in the DNA; that is, it induces a transition mutation. When hydroxylamine was applied to the organism that made the mRNA molecule shown in part a), a strain was isolated in which mutation occurred at the 11th position of the DNA that coded for the mRNA. How many amino acids long would you expect the polypeptide made by this mutant to be? Why? 2) DNA damage by mutagens has serious consequences for DNA replication. Without specific base pairing, the replication enzymes cannot specify a complementary strand, and gaps are left after the passing of a replication fork. What response has E.coli developed to large amounts of DNA damage by mutagens> How is this response coordinately controlled?

Explanation / Answer

1.

Given mRNA sequence: 5'-AUG ACC CAU UGG UCU CGU UAG-3'

Protein sequence: H2N-Met-Thr-His-Trp-Ser-Arg-COOH

Number of amino acids in the peptide = 5

WT mRNA sequence: 5'-AUG ACC CAU UGG UCU CGU UAG-3'

Mutant mRNA sequence: 5'-AUG ACC CAU UAG UCU CGU UAG-3'

Protein sequence = H2N-Met-Thr-His-COOH

The conversion of G to A leads to the formation of a premature termination codon.

2.

DNA repair systems in E coli

1. Direct reversal of DNA damage

2. Excision repair (BER/NER)

Both these are replication-coupled repair systems.

The third repair system is known as post-replication repair.

Related Questions

Navigate

• Browse (All)
• Browse B
• Subjects

---

---

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