Chromosome Mapping In EUKARYOTES (2)

Question 1

Gene linkage

Answer 1

The chromosome (not the gene) is the unit of transmission during meiosis.

Linked genes are not free to undergo independent assortment (keep in mind 2 or more different traits are what undergo independent assortment)

Question 2

T.H. Morgan’s work

Answer 2

1st to discover X linkage.
Studied the SOURCE of gene separation and FREQUENCY:

Proposed 3 things:

• chiasmata = Pt of genetic exchange.
• crossover caused unique phenotypes to occur (aka the recombinant gametes).
• genes close together are less likely to have a chiasma form and crossover.

Question 3

Sturtevants work

Answer 3

He realized that Morgan’s proposal could be used to map the sequence of linked genes.

Suggested that recombinant frequencies between linked genes are additive. This is how you could map positions.

Question 4

What is interference in relation to crossing over

Answer 4

The INFLUENCE that a crossover has of INTERFERING with an ADJACENT region of the chromosome

Question 5

Where does crossing over occur?

Answer 5

On NON sister chromatids at the chiasma