Three Point Linkage Analysis

Question 1

What is Three-point linkage?

Answer 1

Method used to determine the loci of three genes in an organisms genome.

More accurate system compared to two-point linkage

Question 2

How does three-point linkage differ from two-point linkage?

Question 3

How do we perform three-point linkage?

Question 4

How do you calculate recombinant distance? (from %)

Answer 4

RC% R(I) = ((SCO(RI) + DCO)/ total) x 100

RC% R(II) = ((SCO(RII) + DCO)/ total) x 100

Distance is in cM or m.u.

Question 5

What is interference?

Answer 5

Interference is the phenomenon that reduces the probability of another chiasma forming in the vicinity that one chiasma has already formed in, i.e., it reduces the probability of a double crossover from occurring.

This is thought to be due to the physical inability of the chromatids to bend back upon themselves within certain minimum distances.

Interference is higher near the centromere and telomere.

Question 6

How do we calculate interference?

Answer 6

Coefficient of coincidence is the measure of interference.

Interference= 1-CC
(CC= Obs. DCO/ Expected DCO)

Obs DCO- from the given number of org. values
Expected DCO- product of the two single crossovers