Question

In some bees, thin stripes (S) are dominant over thick stripes (s) and black eyes (B) are dominant over gray eyes (b). Complete a dihybrid cross for parents with the genotypes: SsBB × ssBb and answer the following in complete sentences.

1. Describe how you would set up a Punnett square for this cross.
2. List the likelihood of each possible offspring genotype.
3. List the likelihood of each possible offspring phenotype.
(5 points)

Answer 1

There are three parts of this question:

1:Describe how you would set up a Punnett square for this cross.

For making a punnet square we need to cross the given parent details:

P1: SsBB × ssBb

Gametes: SB: sB : sb

Now we will easily draw a cross which is depicted in attached image.

2. List the likelihood of each possible offspring genotype.

As it is mentioned in the question that , thin stripes (S) are dominant over thick stripes (s) and black eyes (B) are dominant over gray eyes (b). Now we see below genotypes in below mentioned ratio:

Genotype: SsBB: ssBB: SsBb: ssBb

Ratio: 4 : 4 : 4 : 4

It means that Likelihood genetic occurences is as:

SsBB: 25 % , ssBB: 25 %, SsBb:25 % and ssBb:25 %

3: Likelihood of phenotypic ratio is as:

• thin striped black eye : 50%
• thick striped black eye : 50%

Hope it helps!