Chapter 27: Recombination

Recombination

Exchange of genetic information between two chromosomes or other molecules of DNA.

Crossover

Structure formed when the strands of two DNA molecules are broken and joined to each other.

Heteroduplex

A DNA double helix composed of single strands from two different DNA molecules.

Chi site

Specific sequences on the DNA of prokaryotes where crossovers form.

Patch recombinants

DNA double helix with a short patch of heteroduplex due to transient formation of a crossover.

Resolvase

Enzyme that carries out resolution of DNA.

Site-specific recombination

Recombination between two lengths of DNA that are largely unrelated, involving integrases that recognize specific sequences and form crossovers.

Gene conversion

Recombination and repair of DNA during meiosis that leads to replacement of one allele by another, resulting in a non-Mendelian ratio among progeny.

Homologous recombination

Recombination between two lengths of DNA that are identical, or nearly so, in sequence regions of the DNA.

Nonhomologous recombination

Recombination between two lengths of DNA that are largely unrelated, involving specific proteins for crossover formation.

Holliday junction

DNA structure formed during recombination at the crossover point where two DNA molecules are joined.

Resolution (of Holliday junction)

Cleavage of the junction where two DNA molecules are fused together, releasing two separate DNA molecules.

Chi sites

Short DNA sequences that signal the RecBCD enzyme to repair DNA double-strand breaks.

chi site recognition

recognized as single-stranded DNA passes through the tunnel in the RecC subunit

RecA

Protein that binds to a single strand with a free 3’ end and inserts it into another DNA double helix, forming a temporary triple helix.

Lambda phage integration

Process by which bacterial DNA and λ-phage DNA align at 'O' region and undergo double-stranded breaks resolved by integrase and excisionase.

Eukaryotic cell cycle for recombination

Prophase I stage of meiosis where homologous chromosomes pair up, allowing for genetic exchange through crossing over.

Gene conversion mechanism

Leads to replacement of one allele by another during meiosis, resulting in a non-Mendelian ratio among progeny.