The following is data from a cross of a heterozygous drosophila female and a hom
ID: 65672 • Letter: T
Question
The following is data from a cross of a heterozygous drosophila female and a homozygous recessive male. The data is examining three linked genes. Use the data to determine:
1) The order of the genes on the chromosome.
2) The pattern of the genes on the female’s pair of chromosomes.
3) The map distances between the genes.
Table 1 Drosophila Cross data 1000 F1 progeny scored for 3 linked loci
Trait
number
Smooth abdomen(sa)
3
Lobe Eye(le) and withered wings (ww)
2
Lobe eye (le)
87
withered wings and smooth abdomen
76
Wild type(+, +, +)
390
Lobe eyes, withered wings and smooth abdomen
344
Withered wings
45
Lobe eyes and smooth abdomen
53
Trait
number
Smooth abdomen(sa)
3
Lobe Eye(le) and withered wings (ww)
2
Lobe eye (le)
87
withered wings and smooth abdomen
76
Wild type(+, +, +)
390
Lobe eyes, withered wings and smooth abdomen
344
Withered wings
45
Lobe eyes and smooth abdomen
53
Explanation / Answer
1. From the double crossover we can say that the order of genes is ww, sa, le.
2.
Trihybrid cross
S. No.
Genotype
Number
Progeny type
1
Smooth abdomen(sa)
3
Double crossover
2
Lobe Eye(le) and withered wings (ww)
2
Double crossover
3
Lobe eye (le)
87
Single cross over
4
withered wings and smooth abdomen
76
Single cross over
5
Wild type(+, +, +)
390
Parental
6
Lobe eyes, withered wings and smooth abdomen
344
Parental
7
Withered wings
45
Single cross over
8
Lobe eyes and smooth abdomen
53
Single cross over
1). From the double crossover, we can say that these genes are in the order of ww sa le.
3). The gene distance between ww and sa loci is = (3+45+53+2/1000) *100 = 10.3 m.u.
Distance between le and ww loci = (3+ 87+ 76 +2/ 1000)* 100 = 16.8 = 16.8 m.u (map units).
Now, the distance between ww and le loci = 10.3 + 16.8 = 27.1 map units
S. No.
Genotype
Number
Progeny type
1
Smooth abdomen(sa)
3
Double crossover
2
Lobe Eye(le) and withered wings (ww)
2
Double crossover
3
Lobe eye (le)
87
Single cross over
4
withered wings and smooth abdomen
76
Single cross over
5
Wild type(+, +, +)
390
Parental
6
Lobe eyes, withered wings and smooth abdomen
344
Parental
7
Withered wings
45
Single cross over
8
Lobe eyes and smooth abdomen
53
Single cross over
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.