Question

1. How would a mutation in the poly(A)-binding protein gene affect translation? How would an electron micrograph of polyribosomes from such a mutant differ from the normal
pattern?

2. Eukaryotes have repair systems that prevent mutations due to copying errors and exposure to mutagens. What are the three excision-repair systems found in eukaryotes, and
which one is responsible for correcting thymine-thymine dimers that form as a result of UV light damage to DNA?

3. What is the name given to the process that can repair DNA damage and generate genetic diversity? Briefly describe the similarities and differences of the two processes.

Answer 1

1.Restriction digestion analysis of isolated band previously subjected to reverse transcription and PCR amplification in vitro shows that mutation of the poly (A) inhabited removal of last intron during splicing,but not the removal of intron upstream .

2.Enzyme based repair mechanism prevent and repair mutation and damage to DNA in Eukaryotes

• DNA polymerase proofreading:-If any nucleotide is mismatchedly insearted during replication.It is corrected 3prime-5 exonuclease activity.
• Nucleotide excision repair:- Damaged region of DNA is unwind and removed by specialized protein .New DNA is synthesized by DNA polymerse.
• Photoreactivation:-Photolyse enzyme is activated by UV light and splitt abnormal base dimer apart.It is also called light repair

demethylating DNA repair enzyme:-Repair damage of DNA by alkylation .

3.DNA repairing process is called proof reading of DNA.Recombination of genome is called genetic diversity.

One differences between both is that DNA repair occurs in the newly syntheized DNA but genetic recombination occurs between homologous chromosome .