1 In watermelons Bitter Fruit B is dominant over sweet b and

1. In watermelons Bitter Fruit (B) is dominant over sweet (b) and Yellow spots (Y) is dominant over no spots (y). Give the gametes for the following melons.

a) BbYy

b) Bbyy

c) bbyy melons can only make gametes that have a genotype of by. Why does this still follow the 2ⁿ formula?

2. How many possible gametes are there if following 3 genes, each with 2 alleles?

3. In Drosophia, red eyes (E) are dominant over white (e) and normal wings (W) are dominant over shriveled wings (w).

What is the genotype of a fruit fly with white eyes and shriveled wings?______

Draw the Punnett Square for a cross between Eeww and EeWw.

What proportion of the offspring have white eyes and shriveled wings?________

Solution

a.BbYy genotype: gametes- BY, By, bY, by

b. Bbyy genotype: ganetes- By, by

c.bbyy genotype according to the 2ⁿ formula should 2² or 4 types of gametes; but due to independent assortment, the only type of gametes being formed is by. (All the four possibilities of gametes being formed is by).

2. According to the 2ⁿ formula, number of possible gametes following 3 genes, each with 2 alleles are 2³ or 8.

3. Genotype of a fruit fly with white eyes and shriveled wings is eeww.

Eeww…..X……….. EeWw

Gametes: Ew, ew…………………EW, eW, Ew, ew

Gametes

EW

Ew

eW

ew

Ew

EEWw (red eye, normal wing)

EEww (red eye, shriveled wing)

EeWw (red eye, normal wing)

Eeww (red eye, shriveled wing)

ew

EeWw (red eye, normal wing)

Eeww (red eye, shriveled wing)

eeWw (white eye, normal wing)

eeww (white eye, shriveled wing)

1/8 or 12.5% of the flies have white eyes and shriveled wings.