Question

6. How would nucleotide excision repair be affected if one of the following proteins was missing? Describe the condition of the DNA if the repair was attempted in the absence of the protein. a) UvrA b) Uvrc c) UvrD d) DNA polymerase

Answer 1

Ans 6)

1. UvrA – If the DNA repair took place in absence of UvrA is that it will not be able to detect the damage properly. When there is damage, it is located by the UvrA protein as it runs along the DNA strand. When the UvrA protein is absent, it is not able to recognize the damage and hence the repair cannot be done.
2. UvrC – The protein after the recognition of the damage is recruited on the DNA and it helps in cleaving the DNA. It cleaves the DNA at 4^th or 5^th phosphate 3’ and also at the 8^th phosphate from the 5’-end site. This helps in cleaving so that the repair and correction can be made. If this is missing, the repair cannot be made due to lack of excision.
3. UvrD – It helps in removing the oligonucleotide and hence gradually the gap is filled with help of the polymerase I. When UvrD is not present, it is not able to remove the oligonucleotides that need to be removed after the excision.
4. DNA polymerase – After finding the part that needs to be excised and removed, it is important that once it is removed, the new nucleotides are filled or added with help of DNA polymerase. Without this, it will not be able to add the new nucleotides.