DNA damage repair by non-homologous end joining (NHEJ)

a. occurs during gene conversion.

b. is responsible for the repair of O6meG adducts.

c. is absent in Xeroderma pigmentosum (XP)

d. result in the loss of genetic information.

e. repair spontaneous DNA depurination.

d. result in the loss of genetic information.

Explanation:

Breaks in the two strands of the same DNA molecule occur in cells under various circumstances and constitute a major threat to genome integrity because they result in the loss of genetic information. If not repaired, they can cause cell death and, in multicellular organisms, can cause cancer. A wide variety of exogenous agents, including ionizing radiation and a considerable number of chemotherapeutic agents (such as bleomycin), cause such breakdowns as well as endogenous agents, such as free radicals.

The main mechanism of repair of these double breaks, which commonly occurs in mammals, is called non-homologous extremity union. In this mechanism, the ends of a DNA molecule, although missing some nucleotides by spontaneous degradation, are juxtaposed to recombine. The same enzyme complex carries out the binding process between the two ends. In this way, the original DNA sequence ends up being changed.