Chapter 22 - Homologous Recombination

What is homologous recombination?

Exchange of DNA between homologous DNA sequences

When does homologous recombination occur in meiosis?

During crossing over (chiasma formation)

What role does homologous recombination play in DNA repair?

Fixes double-strand breaks using a homologous template

What is intramolecular recombination?

Recombination within a single DNA molecule

What is intermolecular recombination? 

Recombination between two different DNA molecules

What enzyme complex begins the RecBCD pathway?

The RecBCD protein (RecB, RecC, RecD)

What type of damage does the RecBCD pathway repair?

Double-strand DNA breaks

What is the Chi site sequence?

5’GCTGGTGG-3’

What does RecA do?

Promotes strand invasion and searches for homology

What structure forms after strand invasion?

The D-loop

What is a Holliday junction?

A four-stranded DNA structure formed during recombination

Which proteins drive branch migration?

RuvA and RuvB

Which protein resolves the Holliday junction?

RuvC

What is gene conversion? 

Non-reciprocal transfer of genetic information 

When does gene conversion occur?

During homologous recombination (e.g., meiosis)

What can gene conversion lead to?

Correction of mismatched bases or reversal of muatations

What enzyme cuts and inserts DNA-only transposons?

Transposase

What are the two types of DNA-only transposon movement?

Cut-and-paste and replicative

What type of genome do retroviruses have?

RNA genome

What enzyme do retroviruses use to make DNA from RNA?

Reverse transcriptase

What happens after retroviral DNA is made?

It integrates into the host genome

What happens after integration?

Host transcribes viral DNA → viral RNA produced