Class 20: Homologous Recombination

What is homologous recombination?

A process that requires homologous sequences, allowing for genetic exchange between similar DNA sequences.

What are homologous sequences?

DNA sequences that share high levels of sequence identity with one another.

Give an example of homologous sequences.

Maternal and paternal copies of a chromosome or sister chromatids after replication.

What is the significance of anti-parallel strands in homologous recombination?

They can base pair with one another, facilitating genetic exchange.

Why is homologous recombination essential during meiosis 1?

It leads to crossing over, which results in genetic diversity in gametes.

What is crossing over?

The exchange of genetic material between homologous chromosomes during meiosis.

How does homologous recombination contribute to genetic variation in offspring?

It creates different combinations of alleles in gametes.

What is the role of Rad51 in homologous recombination?

It catalyzes the base pairing between homologous chromosomes.

What initiates homologous recombination during meiosis?

Double-strand breaks in the DNA.

What is branch migration in homologous recombination?

The movement of the crossover site along the DNA during recombination.

What happens during mismatch repair in meiosis?

The repair mechanism corrects mismatches in base pairing by cutting and filling in the gaps.

How does the presence of heteroduplex regions affect genetic diversity?

Heteroduplex regions can have mismatches that lead to variations in alleles.

What occurs at the double-strand break during homologous recombination?

Exonucleases remove nucleotides to create three-prime overhangs for base pairing.

What is the end result of ligation in homologous recombination?

Formation of covalently bonded connected chromosomes.

Explain the significance of the X's in the diagram of crossing over during meiosis.

They represent the points where genetic material is exchanged between homologous chromosomes.