ümberkombinatsioon

**Ümberkombinatsioon** (also referred to as *recombination* or *crossing-over*) is a fundamental biological process that occurs during meiosis, the type of cell division that produces gametes (sperm and egg cells). It involves the exchange of genetic material between homologous chromosomes, leading to the creation of new combinations of alleles on those chromosomes.

During prophase I of meiosis, homologous chromosomes pair up in a process called synapsis, forming structures known as tetrads or bivalents. At this stage, segments of non-sister chromatids may break and reattach to the corresponding segments of the other chromatid in a reciprocal exchange. This crossover event ensures genetic diversity by shuffling the genetic material between maternal and paternal chromosomes.

Ümberkombinatsioon plays a critical role in increasing genetic variation within populations, which is essential for evolution and adaptation. It also helps repair DNA damage and maintain chromosome stability. The frequency and location of crossovers are influenced by factors such as genetic distance, chromatin structure, and regulatory proteins.

In molecular terms, recombination can occur through different mechanisms, including homologous recombination (precise exchange between similar DNA sequences) and non-homologous recombination (less precise, involving unrelated sequences). Errors in recombination can lead to genetic disorders or chromosomal abnormalities, such as deletions, duplications, or translocations.

Beyond its biological significance, recombination is also a key concept in genetics and evolutionary biology, used to map genes, study inheritance patterns, and understand the genetic architecture of traits. Techniques like genetic linkage analysis rely on recombination frequencies to estimate the relative positions of genes on chromosomes.