Question

In Drosophila melanogaster, the recessive mutant genes are: sable (sb), echinus (ec), and wider (wd) were found to be linked on chromosome 1. The numbers of phenotypes from a trihybrid test cross are shown below: wild type sable, echinus, wider 1050 1065 sable 82 wider, echinus 101 echinus 2317 wider, sable 2285 wider 379 sable, echinus 372 What is the interference value? O 65.4% There is no interference. 5.2% 3.6% O 34.6%

Answer 1

Answer is 34.6%

The greater number are of parental type and the lowest number are of double cross over.

double cross over wild type sb+ ec+ wd+ 1050 sable, echinus, widersb ec wd 1065 sable sb ec+ wd+ 82 wider, echinus sb+ ec wd 101 echinus sb+ ec wd+ 23177 wider, sable sb ec+ wd 2285 wider sb+ ec+ wd 379 sable, echinus sb ec wd+ 372 parental

The middle gene is swapped between the homologous chromosome during double cross over.

Please look in the image for solution;

sht ec fud ) sht e c wd ol Sb ect wit 82 ASCO Sb ect (ca (Parental Double cross over (D.Co) • wel gene is in middle Order is sh, wd cc. . Gene distance blwn sh and wd is (SCO+DCO JX 100 r sbt wd ect 319 . • sbt wat cc . Total (379+372 +01+82)com sb wd ect 4 sb wd te c 312 ( 7651 = 12. 2016 M Gene distance blwn wel and ec is sbt wateco sb wd ec 1065 (1050+1065 +101782\x" oso 1 165 sb wd ect 8 h 8b+ wat ect 1050 sbt wat ect 1050 2 =2288 x 100 = 30-352 cocfficient of coincidence = observed 0.0 / expected Do Expected DCO 12-207 X30.035 2 x 765 / 100 X 100 = 280.51 cocfficient of coincidence = 101+82-183 280-51280-51 = 0.6523 Interference = \ - coefficient of coincidence = 1-0.65 23 = 0.347 in %. = 0.347X100 = 34-70).

Answer is 34.6%