Question

Problem A disease attacks honeybee larvae in the cells of the hive. Honeybees exhibit two genetically controlled behaviors to stop the spread of the disease. Both behaviors are controlled by a single gene, and both are recessive. The uncap trait causes a worker bee to remove the cover of a cell containing a diseased larva. The remove trait causes a worker bee to remove the larva from the hive. A worker bee possessing both traits will perform both tasks. Show the results of a mating between a queen (female) honeybee and a drone (male) who are both heterozygous for both traits. What is the phenotype ratio in this cross? Be sure to include the behaviors associated with each genotype!

Answer 1

Let “U” be the allele for the dominant uncap trait and “u” be the allele for the recessive uncap trait

Let “R” be the allele for the dominant remove trait and “r” be the allele for the recessive remove trait.

Given, both queen honey bee and drone honey bee are heterozygous for the traits.

So, the genotype of the queen bee and drone honey bee for the traits is UuRr. Gametes that can be formed from the genotype include- UR, Ur, uR, ur.

Punnett square for the cross is as follows:

	UR	Ur	uR	ur
UR	UURR	UURr	UuRR	UuRr
Ur	UURr	UUrr	UuRr	Uurr
uR	UuRR	UuRr	uuRR	uuRr
ur	UuRr	Uurr	uuRr	urur

Dominant traits for both uncap and remove trait (UURR, UURr, UuRR, UuRr) = 9

The behavior of worker bees with this trait is that the bee can neither remove the cover of a cell containing a diseased larva nor can remove the diseased larva from the hive.

Dominant trait for uncap trait and recessive trait for remove trait (UUrr, Uurr) = 3

The behavior of the worker bees with this trait is that they cannot remove the cover of a cell containing a diseased larva but they can remove the diseased larva from the hive.

Recessive trait for uncap trait and dominant trait for remove trait (uuRR, uuRr) = 3

The behavior of the worker bees with this trait is that they can remove the cover of a cell containing a diseased larva but they cannot remove the diseased larva from the hive.

Recessive traits for both uncap and remove trait (uurr) = 1

The behavior of the worker bees with this trait is that they can remove the cover of a cell containing a diseased larva and also they can remove the diseased larva from the hive.

So, the phenotypic ratio is 9:3:3:1