Question

5a. You are performing a cross to test if w gene is located on autosomal or sex chromosome. You conduct two reciprocal crosses between w flies and w+ flies.

What outcome would you anticipate if w and w+ alleles were located on an autosomal chromosome?

Make a punnet square to predict the distribution of alleles among the offspring for each cross. Describe what the offspring of different sexes will look like.

5b..What outcome would you anticipate if w and w+ alleles were located on a sex chromosome?

Make a punnet square to predict the distribution of alleles among the offspring for each cross. Describe what the offspring of different sexes will look like.

Answer 1

1)a) let consider is dominant over w allele.(that is red eyecolour dominant over white eye).

so let consider if these genes were located on autosomal chromosome,

Here we are crossing between and (between red and white eyed individuals)

and here the reciprocal cross also same.

so the progenies are , that is red eyed individuals.

now we are crossing between two

Here we are getting red eyed homozygous and heterozygous individuals and white eyed individual.

b) if we are considering this as X linked dominant trait,

then initially we are crossing red eyed female with white eyed male and obtain F1 and F2 and similerly ,

then in reciprocal cross white eyed female with red eyed male.

that is initially then we get progenies as

which is red eyed female

which is red eyed male . So now we are crossing between them.

So here we get homozygous red eyed female, heterozygous red eyed female, red and white eyed male and the genotype as shown above.

Now we are going to perform reciprocal cross, that is the parents are

So the progenies are and .

Now we are crossing these two,

so here we get white eyed female, red eyed female(heterozygous),red and white eyed male.