1. You want to determine the linear order and genetic distance between three gen
ID: 161942 • Letter: 1
Question
1. You want to determine the linear order and genetic distance between three genes on chromosome II in Drosophila. The recessive mutant alleles are g, m, and o. You cross heterozygous females to homozygous recessive males, score the phenotypes of progeny and obtain the following:
540 g m +
560 + + o
162 + m +
170 g + o
245 g + +
240 + m o
46 g m o
37 + + +
a) Determine the orientation of mutant vs. wild type alleles on the female parent’s chromosomes and then determine the gene order.
b) Calculate the distance between the three genes and draw the genetic map.
d) Calculate interference and provide a brief verbal interpretation of your result.
Explanation / Answer
a) The female is heterozygous and the maximum no. of offsprings are in the combination g m + and ++ o. So these are the parental types. Hence the orientation of mutant and wild type alleles on the female parent's chromosome is that the mutant allele g and m are present on the same chromosome and the o allele on the other.
parental type g m + 540
+ + o 560 Total 1100 Total no. of all the progenies together = 2000
C.O between +++ 37
m and o+ gmo 46 Total 83 Recombination percentage 83.100/2000 =4.1
C.O between g + + 245
g and o+ + m o 240 Total 485 " 485.100/2000 = 24.25
C.O between g + o 170
g and m + m + 162 Total 332 " 332.100/2000 =16.6
As C.O percentage between m and o is least, so they are closest. so the gene order is g m o.
b)Distance between g and m is 16.6 map distance. Distance between m and o is 4.1 map distance. distance between g and o is 24.25 map distance.
g m o
The genetic map -------------------------------------
----16 unit-----------/---4.1 unit
----------------24.25 unit-------
c) Interference is negative. Actual percentage of double c.o is more than expected .
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.