KCET · BIOLOGY · STD 12 - 4. Principles of Inheritance and Variation

A human male is heterozygous for autosomal genes 'A' and 'B'. He is also hemizygous for haemophilic gene 'h'. What percentage of sperms will carry 'abh' genotype?

A 25%
B 50%
C 75%
D 0%

Verified Solution

Answer & Solution

Correct Answer

(A) 25%

Step-by-step Solution

Detailed explanation

(A) 25%,
The genotype of human male should be \(AaBb X ^{ h } Y\). Thus, \(2 \times 2 \times 2=8\) types of gametes would be formed that included \(AB X ^{ h }, ABY , aB X ^{ h }, aB Y , Ab X ^{ h }, AbY , ab X ^{ h }, abY\). Clearly only \(1 / 8^{\text {th }}\) proportion that is \(25 \%\) of his sperms would be \(a b h\).

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

Match the type of immunity listed in column-I with the examples listed in column-II. Choose the answer that gives the correct combination of alphabets of the two columns:

Column-I (Types of immunity)	Column-II (Example)
A. Natural active	p. Immunity developed by heredity
B. Artificial passive	q. From mother to foetus through placenta
C. Artificial active	r. Injection of antiserum to travellers
D. Natural passive	s. Fighting infections naturally
	t. Induced by vaccination

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