How Do Eukaryotes Repair Damaged Dan?

nucleotide excision repair (NER

How does damaged DNA get repaired?

Most damage to DNA is repaired by

removal of the damaged bases followed by resynthesis of the excised region

. Some lesions in DNA, however, can be repaired by direct reversal of the damage, which may be a more efficient way of dealing with specific types of DNA damage that occur frequently.

Where does DNA repair happen in eukaryotic cells?

How is DNA damage detected and repaired?

Breaks in DNA reduce the molecular weight of a single DNA strand, and this may be caused by physical, chemical or enzymatic reagents (6).

DNA breaks and lesions may be detected by PCR or using agarose gel electrophoresis

(7). PCR is one of the most frequently used techniques for detecting DNA damage (7).

How are DNA mutations repaired?

Most of the types of DNA damage that are caused by chemical or physical mutagens (Section 14.1. 1) can only be repaired by

excision of the damaged nucleotide followed by resynthesis of a new stretch of DNA

, as shown in Figure 14.18B.

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 is DNA damage and DNA repair?

At least five major DNA repair pathways—

base excision repair (BER), nucleotide excision repair (NER), mismatch repair (MMR), homologous recombination (HR) and non-homologous end joining (NHEJ)

—are active throughout different stages of the cell cycle, allowing the cells to repair the DNA damage.

What are the DNA repair genes?

Homologous recombination

The

BRCA1 and BRCA2

(Breast Cancer 1 and 2) proteins are involved in this repair pathway. The BRCA1 and BRCA2 genes are tumor suppressor genes and the proteins, together with RAD51, form a complex to repair DNA strand breaks (Duncan et al., 1998; Yoshida and Miki, 2004).

How does DNA get damaged?

DNA damage occurs continuously as a result of various factors—

intracellular metabolism, replication, and exposure to genotoxic agents, such as ionizing radiation and chemotherapy

. If left unrepaired, this damage could result in changes or mutations within the cell genomic material.

What are the steps of eukaryotic DNA replication?

DNA replication in eukaryotes occurs in three stages:

initiation, elongation, and termination

, which are aided by several enzymes.

How do eukaryotes repair UV damage?

In eukaryotes, at least three repair systems are known that can deal with base damage:

photoreactivation, excision repair, and post-replication repair

. Photoreactivation is specific for UV-induced damage and occurs widely throughout the biosphere, although it seems to be absent from placental mammals.

How is DNA replication terminated in eukaryotes?

How is DNA repair signaled in cells?

The DNA repair can be signaled in the cells

by the integrity of genome present in the DNA

. The spatial configuration of helix determines the repair activity and it can be cleared by the molecule that binds and gets clear in which it can be recovered.

What might happen to an organism whose DNA is damaged through mutation?

How can mutations affect organisms? Mutations can affect an organism by changing its physical characteristics (or phenotype) or it can impact the way DNA codes the genetic information (genotype). When mutations occur

they can cause termination (death) of an organism or they can be partially lethal

.

Why is DNA damage repaired before cells enter mitosis?

Ideally, if DNA damage is detected, the cells do not enter mitosis until the damage is repaired. Why is DNA damage repaired before cells enter mitosis?

So that healthy daughter cells are produced, allowing the organism to continue to grow

.

What type of repair is activated when damaged DNA has escaped repair and the distortion disrupts the process of replication?

Nucleotide excision repair

is another pathway used to remove and replace damaged bases. Nucleotide excision repair detects and corrects types of damage that distort the DNA double helix.

What are the two types of DNA repair quizlet?

• spontaneous deamination: C forms U, A forms hypoxanthine, G forms xanthine.
• spontaneous depurination: lose a base entirely and form “AP site”
• oxidizing agents: damage by reactive oxygen species (ROS)
• alkylating agents.

What is direct repair of DNA?

Introduction. Direct repair is defined as

the elimination of DNA and RNA damage using chemical reversion that does not require a nucleotide template, breakage of the phosphodiester backbone or DNA synthesis

.

Which enzymes are responsible for most DNA repair?

A special enzyme,

DNA ligase

(shown here in color), encircles the double helix to repair a broken strand of DNA. DNA ligase is responsible for repairing the millions of DNA breaks generated during the normal course of a cell’s life.