Question:
Why is the gene for 'Hypertrichosis of ear' not inherited by daughters?
Why is the gene for 'Hypertrichosis of ear' not inherited by daughters?
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Holandric (Y-linked) traits pass directly from father to all sons.
Daughters never receive a Y chromosome and therefore can never express or transmit Y-linked genes.
Daughters never receive a Y chromosome and therefore can never express or transmit Y-linked genes.
Updated On: Sep 4, 2026
- Because it is a sex-influenced trait
- Because it is a sex-limited trait
- Because it is a Y-linked trait
- Because it is an X-linked recessive trait
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The Correct Option is C
Solution and Explanation
Concept:
Human sex-chromosomal traits are transmitted differently depending on whether the locus is located on the X chromosome or the Y chromosome.
Genes residing exclusively on the non-homologous differential region of the Y chromosome are known as Y-linked or holandric genes.
This question asks for the genetic reason explaining why hypertrichosis of the ear pinna does not appear in female progeny.
Step 1: Mechanism of Y-Linked Inheritance:
Hypertrichosis of the pinna of the ear (excessive hair on the outer ear rim) is a classic example of a Y-linked (holandric) trait.
The gene responsible for this morphological trait is situated on the non-homologous portion of the Y chromosome.
Step 2: Chromosomal Segregation During Fertilization:
Human chromosomal sex determination dictates that:
- Males carry one X and one Y chromosome ($XY$).
- Females carry two X chromosomes ($XX$).
During reproduction, a father passes his single Y chromosome exclusively to his sons, whereas daughters always receive the paternal X chromosome.
Because females completely lack the Y chromosome in their normal karyotype, they never inherit Y-linked traits.
Step 3: Final Answer:
Hypertrichosis of the ear is a Y-linked trait and is transmitted strictly along patrilineal lines from father to son.
Therefore, Option (C) is the correct answer.
Human sex-chromosomal traits are transmitted differently depending on whether the locus is located on the X chromosome or the Y chromosome.
Genes residing exclusively on the non-homologous differential region of the Y chromosome are known as Y-linked or holandric genes.
This question asks for the genetic reason explaining why hypertrichosis of the ear pinna does not appear in female progeny.
Step 1: Mechanism of Y-Linked Inheritance:
Hypertrichosis of the pinna of the ear (excessive hair on the outer ear rim) is a classic example of a Y-linked (holandric) trait.
The gene responsible for this morphological trait is situated on the non-homologous portion of the Y chromosome.
Step 2: Chromosomal Segregation During Fertilization:
Human chromosomal sex determination dictates that:
- Males carry one X and one Y chromosome ($XY$).
- Females carry two X chromosomes ($XX$).
During reproduction, a father passes his single Y chromosome exclusively to his sons, whereas daughters always receive the paternal X chromosome.
Because females completely lack the Y chromosome in their normal karyotype, they never inherit Y-linked traits.
Step 3: Final Answer:
Hypertrichosis of the ear is a Y-linked trait and is transmitted strictly along patrilineal lines from father to son.
Therefore, Option (C) is the correct answer.
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