1. If the proofreading mechanism of the DNA Polymerase fails, what else can the cell do...

1. If the proofreading mechanism of the DNA Polymerase fails, what else can the cell do to fix mistakes?

2. A cell, not during the process of DNA replication, has 2 nucleotides (both T's) that formed a dimer in a single strand. The two dimerized nucleotides aren't base-pairing to the complementary strand.

a) What do you think caused this to occur?

b) what would normally happen in this situation?

C) What if the enzyme, Nuclease, was inactivated in that cell.. what would or wouldn't happen?

d) If there were no nuclease, what would happedn the next time the cell divides ?

Expert Solution

1. If the proofreading mechanism of the DNA Polymerase fails, what else can the cell do to fix mistakes?

Answer: Proofreading is a activity the fucntion of most of the bacterial DNA polymerases. If the proofreading mechanism of the DNA Polymerase fails leads to a thousandfold increase in the rate of spontaneous mutations. But E. coli have an additional mismatch-repair mechanism to check the fidelity of DNA replication by identifying the mispaired nitrogenous bases in newly replicated DNA. Mismatch-repair mechanism determines which strand is to be repaired by distinguishing the newly replicated strand (the one in which an error occurred during replication) from the template strand.

2. a) What do you think caused this to occur?

Answer: This is occured due to exposure of DNA or cell to UV radiation that cuased the formation of thymine dimers.

2. b) what would normally happen in this situation?

Answer: Normally in presence of light the photo-repair mechanism will activate in presence of light and repair the damaged DNA other wise in absence of light the Excision repair mechanism works with the help of nuclease enzyme and remove the dimer and replace it with new nucleotides.

2. C) What if the enzyme, Nuclease, was inactivated in that cell.. what would or wouldn't happen?

Answer: If the Nuclease was inactivated the repair mechanism fails and the dimer structure wouldn't repaired in absence of light by Excision repair mechanism.

d) If there were no nuclease, what would happedn the next time the cell divides ?

Answer: When cell divides leads to misincorporation of wrong nucleotides at the site of thymine dimer and leads to mutation in dividing cells

gladiator answered 2 years ago

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