a. in drosophila\'s autosomal gene T there are two alleles: T and t. when the re

Question

a. in drosophila's autosomal gene T there are two alleles: T and t. when the reccecive t allele is homozygous, it turns female drosophila (XX) into male (phenotypeically only). all those "males" are futile. allele t has no effect on XY male. an hybridization is conducted between heterozygote female for T gene and homozygote male to the reccecive gene at the same locus. what is the ration of all the siblings in F2?

b. in an autosomal gene A in drosophila there are 2 alleles: A, a. this gene is lethal when alleles are homozygote. drosophila has also an autosomal gene B which is indipendent on A. when B dominant allele is homozygote, it prevents the death of AA siblings only. what will be the siblings ration on the following hybridization: AaBb x AaBB

c. explain what does "Mendelian traits" means

Explanation / Answer

a- Genotype for heterozygote female for T gene and homozygote male to the recessive gene at the same locus are XXTt & XYtt respectively.

XXTt................X.........................XYtt

Gametes: XT, Xt.............................Xt, Yt

F1: XXTt (female)..................XXtt (female that converts into male)............XYTt (male)............XYtt (male)

Phenotypic ratio= male: female = 3:1

Genotypic ratio= XYtt:XYTt: XXTt:XXtt = 1:1:1:1

For F2, the cross needs to be specified

b- AaBb X AaBB

Gametes: AB, Ab, aB, ab...............................AB, aB

The ones whose genotypes are written in bold dies off as AABB can only survive if A or a allele is homozygote.

Genotypic ratio= AABB: AaBB: AaB = 1:2:2

c- A mendelian trait is a trait that is controlled by a single gene & it follows Medelian Laws of inheritance. Ex- Point mutation that converts Glutamate to Valine in Sickle cell anemia is a Mendelian trait

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