Question

3. Initial cross: Now become familiar with the phenotype of Cy/Pm D/Sh fties and with the phenot of the mutant stock of flies your instructor has chosen for you to identify as to linkage group To locate the selected mutant gene in its linkage group or chromosome, roceed as follows: Select virgin females homozygous for the mutant gene arbitrarily designate the allele as m) that you are to locate. Mate such virgin mutant females to Cy/Pm D/Sb males. 4. What phenotypes can be expected in the Fi generation, assuming the mutant gene (m to be án autosomal récessive gene? a. Will different F1, results be obtained if m is X-linked rather than What will be the Fi phenotypes if the mutant gene is a Dominant? b. 5. What Fi phenotypes were actually observed?

Answer 1

Q4)

Answer:-

There are three possibilities:-

1) Autosomal dominant condition ( All the F₁ flies will show mutation )

2) Autosomal recessive condition ( Only if the genes are present in recessive condition i.e both the alleles are homozygous and recessive )

3) Sex-linked mutation ( Mostly it can be recessive if all the males are affected and no female is affected )

Q4.a)

Answer:-

As already stated, mutant allele will be present on the X-chromosome. It will be definitely expressed in the males. In case of females, presence of mutant gene in recessive state will indicate mutation. (X-linked recessive).

​​​​​​Q4.b)

Answer:-

If the mutant gene is dominant:-

1) It will be expressed in all the offspring of F₁ generation. ( Autosomal dominant )

2) It will be expressed in half of the progeny ( If there is heterozygous genotype of M/M )

3) Possibility to be considered is presence of that gene as X-linked. It will be seen in all the offsprings.

Q5)

Answer:-

Possible phenotypes

1) Cy Pm+/m m (Curly)

2) Cy+ Pm/m m (plum eye)

3) D+ Sb/m m (Stubble)

4) D Sb+/m m (Dichaete)