mitotic recombination

Definition

Target type: biologicalprocess

The exchange, reciprocal or nonreciprocal, of genetic material between one DNA molecule and a homologous DNA region that occurs during mitotic cell cycles. [GOC:elh]

Mitotic recombination is a crucial process in eukaryotic cells that involves the exchange of genetic material between homologous chromosomes during mitosis. It plays a significant role in maintaining genomic integrity, generating genetic diversity, and driving evolutionary adaptation. The process begins with the formation of double-strand breaks (DSBs) in the DNA, often induced by exogenous factors such as radiation or internal cellular processes. These breaks are recognized by specialized proteins that initiate the repair process. One key repair pathway involves homologous recombination, where the damaged DNA is repaired using the intact homologous chromosome as a template. The process involves several steps:

1. **Break Recognition and Resection:** DSBs are recognized by proteins such as MRN complex (Mre11, Rad50, and Nbs1), which initiate the resection process. Resection is the degradation of DNA at the 5' end of the break, creating 3' single-stranded DNA tails.

2. **Strand Invasion and Homologous Pairing:** The 3' single-stranded DNA tails invade the homologous chromosome, forming a displacement loop (D-loop). This invasion is facilitated by the RecA/Rad51 recombinase protein, which binds to the single-stranded DNA and promotes its pairing with the homologous template.

3. **DNA Synthesis and Branch Migration:** Once the invading strand is paired with the homologous chromosome, DNA polymerase extends the invading strand using the undamaged template as a guide. This process is called DNA synthesis. The newly synthesized strand then migrates along the homologous chromosome, displacing the original strand.

4. **Holliday Junction Formation and Resolution:** As the invading strand migrates, it eventually encounters the other end of the break on the homologous chromosome. This creates a cross-shaped structure called a Holliday junction. Holliday junctions are resolved by specialized enzymes, leading to the exchange of genetic material between the two chromosomes.

Mitotic recombination can have several consequences:

* **Gene Conversion:** In some cases, the homologous chromosome serves as a template for the repair of the damaged chromosome. This process can lead to the transfer of genetic information from one chromosome to the other, resulting in gene conversion.

* **Crossover:** The exchange of genetic material between homologous chromosomes during mitotic recombination can result in the formation of new combinations of alleles, known as crossovers.

* **Chromosomal Rearrangements:** In rare cases, mitotic recombination can lead to chromosomal rearrangements, such as deletions, duplications, or inversions.

Mitotic recombination is a highly regulated process that is essential for maintaining genome stability. It ensures that any damage to the DNA is accurately repaired, preserving the integrity of the genetic code. Moreover, it contributes to genetic diversity by generating new combinations of alleles, which can be beneficial for adaptation to changing environments.'
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Proteins (3)

Compounds (23)