AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

FACTORS AFFECTING THE MAPPING

• Genetic map can be constructed only with the help of crossing over percentage. The crossing over percentage is highly modified by Interference and Coincidence.

Interference

• One chiasma formation reduces the probability of another chiasma formation at other points immediately adjacent to the part of the chromosome . This is called Interference.
• The interference is inversely proportional to the crossing over percentage.

Coincidence

• The coincidence is an inverse measure of interference.
• It is a ratio between actual number of double cross overs and the expected number of double cross overs
• If the actual number of double cross overs is zero, then coincidence is zero and interference is complete.
• If the actual number of double cross over is the same as the expected number, coincidence is one and interference is nil .
• When, interference decreases, coincidence increases.
• Coincidence + Interference = 1.0
• So coincidence ranges from 0 to 1.