Question

DNA Repair

1. Most mutations are deleterious. However, in the right environment, mutations can be advantageous. Describe an example where this is the case.

2. Define mutation.

3. What are the three types of mutations that can result from modifications to the nucleotides of the DNA?

4. How are mutated nucleotides repaired?

5. Describe the process of DNA mismatch repair.

6. Why use the old strand of DNA to correct errors during DNA mismatch repair as opposed to the new strand? What may happen if the new strand was utilized instead?

7. What are the two strategies for repairing double-strand DNA breaks? How are they different and how are they similar?

8. Could double-strand DNA breaks ever be advantageous? How can they contribute to speciation?

9. What is the role of homologous recombination in crossing-over?

10. What is the role of mutation in natural selection?

Answer 1

1. The example where the muatation is useful in a particular environment is Sickle cell anemia.The African people who are heterozygous of Sickled gene are protected against the attack of malaral parasite Plasmodium.

2.Mutation is defined as sudden heritable change in the nucleotide sequence of DNA.

3.The three types of mutations that can result from the modification of nucleotides are Transitions (substitution of purines by purines or pyrimidines by pyrimidines), transversions (substitution of purines by pyrimidines or vice versa) and deletions (where a part of sequnce is deleted)

4.Mutated nucleotides are removed by base excision repair process. The DNA Pol.II and Pol.III are involved in this proof reading process during replication..