What are DNA repair mechanisms?

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 is DNA replication repair and recombination?

Recombination repair is a mechanism for generating a functional DNA molecule from two damaged molecules. It is an essential repair process for dividing cells because a replication fork may arrive at a damaged site, such as a thymine dimer, before the excision repair system has eliminated damage.

What is the most common DNA repair mechanism?

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.

How is DNA replication related to DNA repair?

DNA replication is a fundamental and stringently regulated cellular process that ensures the accurate propagation of the cell’s genetic material. DNA repair, like all major cellular functions, including transcription and DNA replication, is a tightly regulated process.

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. For example, in a process called photoreactivation, pyrimidine bases fused by UV light are separated by DNA photolyase (a light-driven enzyme).

What is direct repair of DNA?

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.

What are the 4 steps of replication?

What are the 4 steps of DNA replication?

• Step 1: Replication Fork Formation. Before DNA can be replicated, the double stranded molecule must be “unzipped” into two single strands.
• Step 2: Primer Binding. The leading strand is the simplest to replicate.
• Step 3: Elongation.
• Step 4: Termination.

What are the two types of DNA repair?

There are two general classes of DNA repair; the direct reversal of the chemical process generating the damage and the replacement of damaged nucleotide bases. DNA encodes the cell genome and is therefore a permanent copy of a structure necessary for the correct functioning of a cell.

What can go wrong during DNA replication?

While most DNA replicates with fairly high fidelity, mistakes do happen, with polymerase enzymes sometimes inserting the wrong nucleotide or too many or too few nucleotides into a sequence. But some replication errors make it past these mechanisms, thus becoming permanent mutations.

What is direct DNA repair?

What are the three steps in DNA repair?

How are DNA replication, recombination and repair related?

As the carrier of genetic information, DNA in a cell must be duplicated (replicated), maintained and passed down accurately to the daughter cells. Three distinct processes are designed for this purpose. The ‘three Rs’ of DNA-replication, recombination, and repair. There are certain common features between the three Rs. I.

How is replication carried out in a cell?

DNA is the genetic material. When the cell divides, the daughter cells receive an identical copy of genetic information from the parent cell. Replication is a process in which DNA copies itself to produce identical daughter molecules of DNA Replication is carried out with high fidelity which is essential for the survival of the species.

How are enzymes involved in the replication fork?

The replication fork moves along the parent DNA as the daughter DNA molecules are synthesized. These enzymes bind to both the DNA strands at the replication fork. Helicases move along the DNA helix and separate the strands. Their function is comparable with a zip opener. Helicases are dependent on ATP for energy supply.

How does DNA replication produce two daughter molecules?

Both the strands undergo simultaneous replication to produce two daughter molecules. Each one of the newly synthesized DNA has one-half of the parental DNA (one strand from original) and one-half of new DNA (Fig. 3.2). This type of replication is known as semiconservative since half of the original DNA is conserved in the daughter DNA.