Question

"These are the results of a three point test cross in Drosophila for the three loci cv f v: cv + + = 234, cv f + = 23, + f + = 199, cv f v = 610, cv + v = 315, + + v = 62, + f v = 278, + + + = 338. The map distance between the cv and v loci is 28.99 cM. The map distance between the v and f loci is 29.09 cM. Calculate the Interference correct to 2 decimal places. "

Answer 1

interference =1-coefficent of coincidence

coefficent of coincidence=observed Double cross over/expected Double cross over

expected Double cross over=probability of single cross over between cv and v *probability of single cross over between v and f* total no. of individuals in progeny

map distance is in % so probability of single cross over between cv and v is 0.2899 and 0.2909 in v and f

=0.2899*0.2909*2059=173.639

observed double cross over =62+23=85 genotype with least progeny

coefficent of coincidence=85/173.639=0.4895

interference=1-0.4895=0.5105

it tells us about the Double cross over frequency that will not be observed