DNA Repair Mechanisms

These flashcards cover key concepts related to DNA repair mechanisms, including types of DNA damage, repair processes, and their implications for genetic integrity and disease.

What is the primary purpose of DNA repair mechanisms?

To correct DNA damage and maintain the integrity of the genetic information.

What are the three main stages of DNA repair mechanisms?

1. Excision of damaged part, 2. Resynthesis of new segment, 3. Ligation of newly synthesized DNA.

What is Base Excision Repair (BER)?

A DNA repair process that removes and replaces damaged bases, involving enzymes like DNA glycosylases and DNA polymerase.

What causes depurination in DNA?

The spontaneous loss of purine bases (adenine or guanine) from the DNA.

What is the result of deamination in DNA?

The conversion of cytosine to uracil, which can lead to mutations if not repaired.

Which DNA repair mechanism is specifically involved in correcting mispaired bases after DNA replication?

Mismatch Repair (MMR) corrects replication errors that escape proofreading.

What are the two major types of repair for double-strand breaks?

Nonhomologous End Joining (NHEJ) and Homologous Recombination (HR).

What is Xeroderma Pigmentosum?

A genetic disorder caused by the inability to repair UV-induced DNA damage due to defects in nucleotide excision repair.

What are the consequences of failing to repair DNA damage?

Loss of genetic integrity can lead to diseases like cancer, with mutations accumulating over time.

What is the significance of DNA repair in the context of aging and cancer?

As the efficiency of DNA repair declines with age, the likelihood of mutations increases, leading to a higher incidence of cancer.

What is Nucleotide Excision Repair (NER)?

A major DNA repair pathway that removes bulky DNA lesions, such as those caused by UV radiation or chemical mutagens, by excising a segment of DNA around the damage.

What is the role of DNA ligase in DNA repair?

DNA ligase joins the newly synthesized DNA segment to the existing DNA strand, sealing the nicks in the phosphodiester backbone.

How does Nonhomologous End Joining (NHEJ) repair double-strand breaks?

NHEJ directly ligates the broken DNA ends together without the need for a homologous template, often resulting in small deletions or insertions.

How does Homologous Recombination (HR) repair double-strand breaks?

HR uses a homologous DNA molecule (like a sister chromatid) as a template to accurately repair the break, ensuring no loss of genetic information.

What is the function of DNA glycosylases in Base Excision Repair (

The conversion of cytosine to uracil, which can lead to mutations if not repaired.