Question

HELP PLEASE In the following cross, assume simple dominance and independent assortment for each trait. What proportion of the progeny will be expected to phenotypically resemble the second parent?

AABB x Aabb

1. 1/4

2. 1/8

3. 3/4

4. 3/8

Answer 1

In a cross between AABB and Aabb, to find the proportion of progeny resembling the second parent Aabb, we calculate the individual probabilities for genes A and B (3/4 for A and 1/2 for B) and multiply them together, resulting in 3/8 of the progeny showing the Aabb phenotype.

Step-by-step explanation:

When looking at a cross involving simple dominance and independent assortment, like the cross AABB x Aabb, we can predict the phenotypic ratio of the offspring using both the sum and product rules. To find the proportion of progeny that will phenotypically resemble the second parent (Aabb), we need to calculate the proportion for each gene separately and then apply the product rule.

For gene A, the second parent is heterozygous Aa, so offspring can be Aa or AA to have the dominant phenotype, the chances of which are 3/4 (1/2 heterozygous Aa + 1/4 homozygous AA). For gene B, the parent is homozygous for the recessive b allele, so all offspring must receive a b from this parent, resulting in a 1/2 chance for Bb (heterozygous).

Using the product rule, we multiply the individual probabilities together to find the overall proportion. Therefore, for offsprings to resemble the Aabb parent, we calculate the chance of having A dominant (3/4) and B heterozygous (1/2). The calculation will be 3/4 * 1/2 = 3/8.

Answer 2

0

Step-by-step explanation:

This question involves two genes; A and B. According to the question, two parents are crossed as follows: AABB × Aabb. The parents will produce the following gametes:

AABB- AB, AB, AB, AB

Aabb - Ab, Ab, ab, ab

Using these gametes in a punnet square (see attached image), the offsprings in the following proportion will be produced:

AABb = 4/16 = 1/4

AaBb = 4/16 = 1/4

Therefore, none (0) of the offsprings will resemble the phenotype of the second parent (Aabb).