Chapter 5- Homologous Recombination

Two ways meiosis contribute to genetic diversity through

1) Independent Assortment

2) Crossing Over

Each pair of homologous chromosomes segregate freely from each other.

-Unlinked genes

Independent Assortment

Two homologous chromosomes exchange portions of DNA

-Linked genes

Crossing Over

The production of new allelic combinations through genetic exchange between homologous chromosomes is called

Recombination

Chromosomes that carry a mix of alleles derived from different homologous are called

Recombinants

Type of recombination that happens on 2 homologous non-sister chromatids

Holiday Model

What protein initiates recombination

Spo11

How does Spo11 initate recombination

By breaking phosphodiester bonds of both strands on one chromatid

5’ ends of each broken strand are degraded by what enzyme to create a 3’ single strand

Exonuclease

What protein helps the 3’ single strand trail invades non-sister chromatid to form heteroduplex

DMC1 (strand invasion)

Once the second holiday junction forms what 3 things happen

1) Second heteroduplex forms

2) DNA synthesis takes over

3) DNA ligase reseals the DNA backbone

How is the heteroduplex lengthen

Branch migration

The holiday junction is resolved by what type of cuts

Horizontal & Vertical Cuts

What enzyme make these horizontal & vertical cuts

Resolvase

Enzyme that disentangles the invading strand from the non sister chromatid preventing Holiday Junction from forming

Anti crossover helicase

Holiday junctions are nearly random

True

Site specific recombination promotes breakage and rejoining of DNA molecules shorter than

200 bp

Enzyme that catalyzes all breakage and joining steps in site-specific recombination

Recombinase

CRISPR-CAS-9

Uses RNA for case site-specific recombination at genetic locations.

Naturally occurring

FLP/FRI & Cre recombinase / lox p

Scientist manipulated recombination

Artificially occurring

Breakage and rejoining of DNA strands to produce separate chromatids at the end of recombination is called

Resolution

During recombination, the DNA strand displaced by an invading strand forms a

D-loop

As a result of strand invasion, a DNA segment is formed from one strand from each non-sister chromatid. This type of DNA segment is called a

Heteroduplex

During resolution of a double Holiday Junction intermediate __ breaks DNA strands at each junction and __ joins them

Resolvase, DNA Ligase

Movement of a Holiday junctions away from each other is called

Branch Migration

Which of the following can lead to gene conversion during recombination

Mismatch repair of a heteroduplex