The recessive scute bristles (s) and ruby eyes (rb) identify two autosomal linke

Question

The recessive scute bristles (s) and ruby eyes (rb) identify two autosomal linked genes of flies. When female heterozygous for the genes were crossed with scute-bristled, ruby-eyed males, the following classes and number of progeny (out of 1000) were obtained:

Wildtype bristles, wildtype eyes

188

Scute bristles, wildtype eyes

307

Wildtype bristles, ruby eyes

313

Scute bristles, ruby eyes

192

Do the genes for wildtype bristles and scute bristles assort independently? Your null hypothesis would be: The genes for bristle texture are not linked but assort independently. Do you accept or reject the null?

Wildtype bristles, wildtype eyes

188

Scute bristles, wildtype eyes

307

Wildtype bristles, ruby eyes

313

Scute bristles, ruby eyes

192

Explanation / Answer

Answer: the Null hypothesis is rejected.

Explanation:

scute bristles = s = recessive trait

ruby eyes = rb = recessive trait

Parental cross: s/+ rb/+ X s/+ rb/+

If both genes are unlinked, the phenotypic ratio would be

+_ +_ = WT bristles and WT eyes = 9 = (1000/16) X 9 = 562.5

ss +_ = Scute bristles and WT eyes = 3 = (1000/16) X 3 = 187.5

+_ rbrb = WT bristles and ruby eyes = 3 = (1000/16) X 3 = 187.5

-/- -/- = Scuty bristles and Ruby eyes = 1 = (1000/16) X 1 = 62.5

However, the given values are completely different. Hence the null hypothesis is rejected i.e. both the genes are linked.

Please rate the solution. Your efforts are highly appreciated. Thank you.

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