Question

Bulky lesions: Which of the following is the region of distorted DNA double helix signaling the need for nucleotide excision repair?

1) Region of disorted DNA double helix signaling need for nucleotide excision repair
2) Another term for the chromosome puffs observed in the polytene chromosomes
3) The shape of the RNA polymerase tail following phosphorylation
4) The temporary separation of a base from its complement to allow close inspection by repair enzymes

Answer 1

The region of distorted DNA signaling the need for nucleotide excision repair is where DNA damage has caused helix-distorting lesions, prompting repair enzymes to remove and replace damaged sections with correct nucleotides.

Step-by-step explanation:

The region of the distorted DNA double helix signaling the need for nucleotide excision repair (NER) is where the DNA damage occurs, leading to lesions that can disrupt the helical structure. This process specifically targets helix-distorting damage such as thymine dimers, commonly caused by UV light, and larger scale single-strand breaks.

During NER, enzymes such as the UvrABC endonuclease complex recognize the distortion, make incisions on both the 5' and 3' sides of the lesion, remove the damaged section, and then a DNA polymerase and DNA ligase work together to fill in the gap with correct nucleotides and seal the backbone. This repair mechanism is essential for maintaining the integrity of the DNA and preventing mutations that could lead to diseases such as cancer.

The region of distorted DNA double helix signaling the need for nucleotide excision repair is known as bulky lesions. This type of repair mechanism is employed when UV exposure causes the formation of pyrimidine dimers. In this process, enzymes replace incorrect bases by making a cut on both the 3' and 5' ends of the incorrect base and the segment of DNA is removed and replaced with the correctly paired nucleotides.