What are the three major mechanisms of DNA repair?

There are three types of repair mechanisms: direct reversal of the damage, excision repair, and postreplication repair. Direct reversal repair is specific to the damage.

What are the types of DNA damage?

DNA damage can be subdivided into two types: (1) endogenous damage caused by reactive oxygen species (ROS) that are derived from metabolic byproducts and (2) exogenous damage caused by radiation (UV, X-ray, gamma), hydrolysis, plant toxins, and viruses.

How many types of excision repair systems are known?

Three different types of excision repair have been characterized: nucleotide excision repair, base excision repair, and mismatch repair.

What is the most common mechanism for repairing damage to DNA?

Consequently, the various types of excision repair are the most important DNA repair mechanisms in both prokaryotic and eukaryotic cells. In excision repair, the damaged DNA is recognized and removed, either as free bases or as nucleotides.

What are the 4 types of point mutations?

Types of Point Mutations. We are going to focus on the following point mutations: frameshift, silent, nonsense, and missense. Let’s start with a frameshift mutation, where there’s an insertion or deletion of one or more bases.

What is the purpose of a DNA primer?

The synthesis of a primer is necessary because the enzymes that synthesize DNA, which are called DNA polymerases, can only attach new DNA nucleotides to an existing strand of nucleotides. The primer therefore serves to prime and lay a foundation for DNA synthesis.

What are the two types of DNA repair?

There are two main mechanisms for repairing double strand breaks: homologous recombination and classical nonhomologous end joining. Homologous recombination involves the exchange of nucleotide sequences to repair damaged bases on both strands of DNA through the utilization of a sister chromatid.

What are 3 types of point mutations?

These groupings are divided into silent mutations, missense mutations, and nonsense mutations.

What are the 5 types of gene mutations?

Summary

• Germline mutations occur in gametes. Somatic mutations occur in other body cells.
• Chromosomal alterations are mutations that change chromosome structure.
• Point mutations change a single nucleotide.
• Frameshift mutations are additions or deletions of nucleotides that cause a shift in the reading frame.

What is NER and BER?

NER and BER are two types of DNA excision repair processes found in cells. BER is able to repair small damages caused endogenously while NER is able to repair damage regions up to 30 base pair length caused mostly by exogenously.

What is the difference between mismatch repair and nucleotide excision repair?

Nucleotide excision repair repairs the modified nucleotide damages, typically those significant damages of the DNA double helix which happen due to exposure to U.V irradiation and chemical adducts. Mismatch repair proteins recognize the wrong nucleotide, excise it and replace it with correct nucleotide.

What enzymes are used in DNA repair?

DNA nucleases catalyze the cleavage of phosphodiester bonds. These enzymes play crucial roles in various DNA repair processes, which involve DNA replication, base excision repair, nucleotide excision repair, mismatch repair, and double strand break repair.

Which enzyme is responsible for BER?

BER is typically initiated by recognition and excision of a base damage (indicated as a black residue) by a DNA glycosylase. Such enzymes include uracil DNA glycosylase (UNG) and endonuclease VIII-like 1 protein (NEIL1).

What is the NER pathway?

Nucleotide excision repair (NER) is the main pathway used by mammals to remove bulky DNA lesions such as those formed by UV light, environmental mutagens, and some cancer chemotherapeutic adducts from DNA. Deficiencies in NER are associated with the extremely skin cancer-prone inherited disorder xeroderma pigmentosum.