Two Point Linkage Analysis

Question 1

What can Recombinant % be converted into to represent distance?

Answer 1

From % to cM (centimorgan) or m.u. (mapping unit)

Question 2

What is a Genetic Map?

Answer 2

Chromosome maps indicating the order of genes along the chromosome and distances between them in cM or mapping units.

1% recombination = 1 mapping unit or  1 cM

Question 3

What is a Physical Map?

Answer 3

Complete sequencing of genomes have resulted in physical maps of chromosome.

These indicate the order of genes along a chromosome and distances between genes in base pairs.

Question 4

What is Two-point linkage mapping?

Answer 4

This is based on a method of mapping genes two at a time and putting them all together in a map.

Question 5

What is the problem with two point linkage mapping?

Answer 5

It is accurate for short distances but if the distance between genes are greater than 10 cM, it tends to underestimate the distance.

Longer the unmarked distance between genes greater the probability of a double crossover occurring in that region

Double crossovers results in parental type gametes and hence goes un-noticed in the calculation of RC % and hence m.u.

Under-estimation of map distances increases as the distance between gene increases.