47. A well-known genetic disorder is carried by a woman. She marries a normal man and her all female child are alive but she tost all male child. Such a disorder must be-
(1) X-linked dominant
(2) X-linked recessive
(3) Y-linked dominant
(4) Autosomal recessive

Introduction
In this pedigree-style question, a woman carrying a well-known genetic disorder marries a normal man; all her daughters survive but all her sons die, which strongly points to a lethal X‑linked recessive disorder where hemizygous males are affected and die, while heterozygous daughters are only carriers. Understanding how X‑linked recessive inheritance works, and why other inheritance patterns do not fit this scenario, is crucial for solving such CSIR/NEET level genetics questions.​

Core genetic reasoning

• A “carrier woman” for a sex‑linked condition almost always refers to a heterozygous female with one normal X and one mutant X.​

• She marries a normal man (genotype XY with normal X), so daughters receive the father’s normal X and one of the mother’s X chromosomes, while sons receive the mother’s X and the father’s Y.​

• In an X‑linked recessive lethal disorder, any son who inherits the mutant X is affected and may die before or soon after birth, whereas daughters inheriting the mutant X are typically carriers but usually survive.​

In the question, “all female child are alive but she lost all male child” exactly matches the expectation that male hemizygotes are non‑viable while carrier females survive, so the disorder must be X‑linked recessive.

Correct answer: (2) X-linked recessive.

Why option (2) X-linked recessive is correct

• In X‑linked recessive inheritance, males with a single mutant allele on their only X chromosome are affected because they lack a second normal copy.​

• A carrier female (X⁺Xᵈ) crossed with a normal male (X⁺Y) typically produces: 25% normal daughters (X⁺X⁺), 25% carrier daughters (X⁺Xᵈ), 25% normal sons (X⁺Y) and 25% affected sons (XᵈY).​

• If the disorder is lethal in hemizygous males, all affected sons (those with XᵈY) will die, while carrier daughters (X⁺Xᵈ) and normal daughters survive, fitting the observation that all daughters live and all sons are lost.​

Examples of such patterns include severe X‑linked immunodeficiencies or metabolic defects where affected male fetuses may not survive, although specific disease names are not required to solve the question.​

Why option (1) X-linked dominant is incorrect

• In X‑linked dominant inheritance, a single mutant allele on the X chromosome produces the disorder in both males and females.​

• A heterozygous affected woman (X⁺Xᴰ) with a normal man (X⁺Y) would have: 50% affected daughters (XᴰX⁺), 50% affected sons (XᴰY), and 50% normal children, not “all normal surviving daughters and all lost sons.”​

• Moreover, if the allele were fully dominant and lethal in males, many affected heterozygous females could also show serious disease or lethality, so the pattern “carrier woman, all daughters alive” is not typical phrasing for an X‑linked dominant condition.​

Thus X‑linked dominant inheritance does not best fit the described scenario.

Why option (3) Y-linked dominant is incorrect

• Y‑linked (holandric) traits are transmitted exclusively from father to son because only males carry a Y chromosome.​

• A Y‑linked dominant disorder in a normal man would be absent, and in any case a carrier or affected woman cannot exist because women lack a Y chromosome.​

• Since the question clearly states that “a woman carries the disorder,” a Y‑linked trait is impossible, so option (3) is ruled out immediately.​

Why option (4) Autosomal recessive is incorrect

• Autosomal recessive conditions appear when an individual is homozygous for a mutant allele on an autosome; carriers are heterozygous and typically unaffected.​

• If the woman is a carrier (Aa) and the man is normal (AA), none of their children (AA or Aa) would be affected, and both sons and daughters would be equally likely to be carriers or normal; there is no reason for only males to die.​

• Even if both parents were carriers (Aa × Aa), affected individuals (aa) would be produced among both sexes in equal proportion, not limited to males, so the observed pattern “all male children lost, all female children alive” cannot be explained by autosomal recessive inheritance.​

Therefore, the inheritance pattern that uniquely explains a carrier woman whose all sons die while all daughters live is X‑linked recessive, making option (2) the correct choice.