15. UV rays can create thymidine dimers. This type of DNA damage is typically fi

Question

15. UV rays can create thymidine dimers. This type of DNA damage is typically fixed by which DNA repair system (circle one). a. Base Excision Repair (BER) b. Nucleotide Excision Repair (NER) c. Proofreading d. Mismatch Repair e. None of the above, replication would be blocked and the cell would die. 6. Replication slippage can occur during replication. If this error in DNA replication is not fixed what type of permanent mutation will be created (circle one)? a. Indel b. Inversion C. Transition d. Transversion e. Translocation Oxygen Radical Damage can cause a guanosine (G) base to be modified to an 8- oxoG (G'). This modified base pairs with Adenine (A). If G* is not fixed, what type of permanent mutation will be created (circle one)? a. Indel b. Inversion c. Transition d. Transversion e. Translocation

Explanation / Answer

15). Three type of excision repair removes the damaged or incorrect sequences. They include Base excision, Nucleotide excision and Mismatch repair.

Base excision repair removes stretch of DNA aided by specific enzymes. Mismatch repair only can correct the Watson-Crick mismatched base pairs.

Thymine dimers are caused by UV rays. This type of DNA damage is typically fixed by Nucleotide excision repair.

Thus the answer is

b). Nucleotide excision repair.

16). Replication slippage, if not fixed, leads to the insertion or deletion of a nucleotide in the DNA strand. This leads to the formation of Indel.

Thus, the answer is

a). Indel

17). If oxoG (G*) is not fixed , then it leads to the G to T permanent mutation. Guanine is a purine while Thymine is a pyrimidine. Mutation leading to the change from Purine to Pyrimidine is called Transversion.

Thus the answer is

d). Transversion

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