BIOL1020 MOD4 WEEK3

What are Linked Genes and how does it work?

Genes that are very close together (shared or adjacent loci) are called linked genes.

Because of the close physical distance between certain genes, inheritance patterns becomes non-independent.

What is crossing over and recombinant?

During prophase I and Meiosis, chromosomes condense, pair up, and exchange pieces of DNA.

When chromosomes cross over, it creates new combinations called recombinant.

How does linkage affect recombinations?

If two genes are located close together (inked), they are very likely to move together during recombination.

Still possible to seperate linked genes by recombination, however it is rare.

How do recombination rates change with linked genes?

When genes are linked, there will always be a lower frequency of recombinant genotype.

Tightly linked genes:

• recombinant = rare

• Parental = abundant

Weakly linked genes:

• Recombinant = uncommon

• Parental = common

Unlinked Genes:

• Equal frequency of both

• Independent assortment

How would you test for Linkage?

Dihybrid test cross -

• a cross between an F1 individual and a homozygous recessive parent.

• Can solve for recombination frequency, which also equals the distance of genes

• Recomb freq% = number of recomb / total number of progeny

How high can a recombination frequency go?

Recombination frequency can never go higher than 50%.