If both parents are carriers for thalassaemia, which is an autosomal recessive disorder, what are the chances of pregnancy resulting in an affected child?

A \(0.25\)
B \(1\)
C No chance
D \(0.5\)

Verified Solution

Answer & Solution

Correct Answer

(A) \(0.25\)

Step-by-step Solution

Detailed explanation

(a): Thalassaemia is an autosomal recessiveblood disorder. In the given case, both the partners are unaffected carriers for the gene \(i.e.\), have heterozygous genotype \(Tt\). Persons homozygous for the autosomal recessive gene of \(\beta\)-thalassaemia suffer from severe haemolytic anaemia. Heterozygous persons are also not normal, but show the defect in a less severe form (thalassaemia minor).

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 List I with List II related to muscular/skeletal system :

List I	List II
A. Tetany	I. Inflammation of joints
B. Arthritis	II. Autoimmune disorder affecting neuromuscular junction
C. Myasthenia gravis	III. Wild contraction in muscle due to low \(Ca ^{++}\)in body fluid
D. Muscular dystrophy	IV. Progressive degeneration of skeletal muscle

Choose the correct answer from the options given below :

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