1. In the housefly red eye color (A) is dominant to green eye color(a). Black bo
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Question
1. In the housefly red eye color (A) is dominant to green eye color(a). Black body colour (B) is dominant to brown body colour(b).
a) Illustrate a cross between a fly homozygous for red eyse andblack body colour and a fly with green eyes and brown body colour.What is the resulting genotype and phenotype of the F1?
b)Illustrate a cross between a fly heterozygous for red eyes andblack body colour and a fly homozygous recessie for bothcharacters. Give the resulting genotypic and phenotypicratios.
c)After predicting the results of the cross in part b), the actualcross between the fly heterozygous for red eyes and black body anda homozygous recessive fly was carried out and resulted in thefollowing numbers of offspring: 174 red-eye-black-bodied flies, 186green-eyed brown-bodied flies, 23 red-eyed brown-bodied flies, and17 green-eyed black-bodied flies. What do these actualresults suggest about the location of the genes for eye coloour andbody colour??
Explanation / Answer
The given data is
Red eye - A
Green eye -a
Black body - B
Brown body - b
A is dominant over a, and B is dominant over b.
A) Genotype of fly homozygous for red eye and black body - AABB
Genotype of fly homozygous for green eyes and brown body - aabb
therefore a cross between these two can be represented as -
AABB X aabb
Therefore, all the flies would have the genotypes as AaBb, with the phenotype as Red eyes and Black body.
B) Genotype of fly heterozygous for red eyes and black body - AaBb
Genotype of fly recessive for both characters - aabb
Therefore, a cross between these would result in the following
Therefore, the genotypes are -
AaBb - Red eyes, Black body
Aabb - Red eyes, Brown body
aaBb - Green eyes, Black body
aabb - Green eyes, Brown body
All phenotypes are in the ratio of 1:1:1:1
C) Since there is a higher percentage of Red eyes-Black bodies, and Green eyes- Brwon bodies, it is sugestive that independent assortment does not take place in the truest sense. There is a high probability that both the genes for eye colour and body colour are linked genes, and they are always inherited together.
ab ab AB AaBb AaBb AB AaBb AaBbRelated Questions
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