Question

How many different types of gametes can be formed by individuals of the following genotypes? What are they in each case? (a) \(A a B b\) (b) \(A a B B\) (c) \(A a B b C c\) (d) \(A a B B c c\) (e) \(A a B b c c,\) and (f) \(A a B b C c D d E e ?\)

Short answer

(a) Genotype: AaBb Answer: 4 gametes: AB, Ab, aB, and ab. (b) Genotype: AaBB Answer: 2 gametes: AB and aB. (c) Genotype: AaBbCc Answer: 8 gametes: ABC, ABc, AbC, Abc, aBC, aBc, abC, and abc. (d) Genotype: AaBBcc Answer: 2 gametes: ABc and aBc. (e) Genotype: AaBbcc Answer: 4 gametes: ABc, Abc, aBc, and abc. (f) Genotype: AaBbCcDdEe Answer: 32 gametes. The different combinations of alleles can be determined systematically using the law of independent assortment.

Step-by-step solution

(a) Genotype: AaBb

There are two possibilities for each gene: A or a and B or b. To determine the number of gametes, we can use the formula \(2^n\), where n is the number of heterozygous gene pairs. Here, n=2. Number of gametes = \(2^2 = 4\) The possible gametes are: AB, Ab, aB, and ab.

(b) Genotype: AaBB

There are two possibilities for the first gene: A or a and only one possibility for the second gene: B. In this case, n=1. Number of gametes = \(2^1 = 2\) The possible gametes are: AB and aB.

(c) Genotype: AaBbCc

There are two possibilities for each gene: A or a, B or b, and C or c. Here, n=3. Number of gametes = \(2^3 = 8\) The possible gametes are: ABC, ABc, AbC, Abc, aBC, aBc, abC, and abc.

(d) Genotype: AaBBcc

There are two possibilities for the first gene: A or a, one possibility for the second gene: B, and one possibility for the third gene: c. In this case, n=1. Number of gametes = \(2^1 = 2\) The possible gametes are: ABc and aBc.

(e) Genotype: AaBbcc

There are two possibilities for the first gene: A or a and two possibilities for the second gene: B or b. Here, n=2. Number of gametes = \(2^2 = 4\) The possible gametes are: ABc, Abc, aBc, and abc.

(f) Genotype: AaBbCcDdEe

There are two possibilities for each of the five genes, meaning n=5. Number of gametes = \(2^5 = 32\) The possible gametes can be systematically determined using the law of independent assortment, resulting in 32 different combinations of alleles.