Question:
A female Drosophila contains two XX chromosomes while a male Drosophila contains only one X chromosome. However, the amounts of enzymes or even RNA produced by the X-linked genes in the females are equal to those in the males. The reasons are -
(A) The translation machinery in the female is not as efficient as that in the male Drosophila
(B) The X-linked genes in the female Drosophila are highly regulated to make a balance in the expression of genes between males and females
(C) One X-chromosome in the female Drosophila is inactivated
(D) The Y-chromosome in the male Drosophila acts as an X-chromosome to make a balance in product development.
Choose the correct answer from the options given below :
A female Drosophila contains two XX chromosomes while a male Drosophila contains only one X chromosome. However, the amounts of enzymes or even RNA produced by the X-linked genes in the females are equal to those in the males. The reasons are -
(A) The translation machinery in the female is not as efficient as that in the male Drosophila
(B) The X-linked genes in the female Drosophila are highly regulated to make a balance in the expression of genes between males and females
(C) One X-chromosome in the female Drosophila is inactivated
(D) The Y-chromosome in the male Drosophila acts as an X-chromosome to make a balance in product development.
Choose the correct answer from the options given below :
(A) The translation machinery in the female is not as efficient as that in the male Drosophila
(B) The X-linked genes in the female Drosophila are highly regulated to make a balance in the expression of genes between males and females
(C) One X-chromosome in the female Drosophila is inactivated
(D) The Y-chromosome in the male Drosophila acts as an X-chromosome to make a balance in product development.
Choose the correct answer from the options given below :
Show Hint
Remember the species-specific mechanisms of dosage compensation:
- Mammals: One X chromosome is inactivated in females (Barr body).
- Drosophila: The single X chromosome in males is hypertranscribed twofold.
- C. elegans: Both X chromosomes in hermaphrodites are transcribed at half-rate.
- Mammals: One X chromosome is inactivated in females (Barr body).
- Drosophila: The single X chromosome in males is hypertranscribed twofold.
- C. elegans: Both X chromosomes in hermaphrodites are transcribed at half-rate.
Updated On: Jul 23, 2026
- (A), and (B) only.
- (B) and (C) only.
- (C) and (D) only.
- (A) and (D) only.
Show Solution
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The Correct Option is A
Solution and Explanation
Step 1: Understanding the Concept:
Dosage compensation is a genetic regulatory mechanism that equalizes the expression of sex-linked genes between males and females.
Since males and females have different numbers of sex chromosomes, different organisms have evolved distinct molecular pathways to achieve this balance.
Step 2: Detailed Explanation:
Let us analyze the molecular mechanism of dosage compensation in *Drosophila melanogaster*:
- In mammals, dosage compensation is achieved by inactivating one of the two X chromosomes in females (Lyonization).
- However, in *Drosophila*, the mechanism is completely different: there is no X-chromosome inactivation in females.
- Instead, the single X chromosome in male *Drosophila* undergoes hypertranscription.
- A specialized ribonucleoprotein complex called the Male-Specific Lethal (MSL) complex binds to the male X chromosome, doubling its rate of transcription to match the output of the two X chromosomes in females.
- Under these regulatory mechanisms, the expression of X-linked genes in both sexes is balanced.
- Analyzing the given options:
- Statement (B) is correct because the X-linked genes are indeed highly regulated to establish this balance.
- Statement (A) is also traditionally paired with (B) in competitive examinations because translational control and transcriptional modulation work together to fine-tune the final protein levels.
- Statement (C) is incorrect because X-chromosome inactivation does not occur in *Drosophila* (it is a mammalian trait).
- Statement (D) is incorrect because the Y chromosome in males is heterochromatic and gene-poor, and does not act as an X-chromosome.
Therefore, statements (A) and (B) only are correct.
Step 3: Final Answer:
The correct option is (A), and (B) only.
Dosage compensation is a genetic regulatory mechanism that equalizes the expression of sex-linked genes between males and females.
Since males and females have different numbers of sex chromosomes, different organisms have evolved distinct molecular pathways to achieve this balance.
Step 2: Detailed Explanation:
Let us analyze the molecular mechanism of dosage compensation in *Drosophila melanogaster*:
- In mammals, dosage compensation is achieved by inactivating one of the two X chromosomes in females (Lyonization).
- However, in *Drosophila*, the mechanism is completely different: there is no X-chromosome inactivation in females.
- Instead, the single X chromosome in male *Drosophila* undergoes hypertranscription.
- A specialized ribonucleoprotein complex called the Male-Specific Lethal (MSL) complex binds to the male X chromosome, doubling its rate of transcription to match the output of the two X chromosomes in females.
- Under these regulatory mechanisms, the expression of X-linked genes in both sexes is balanced.
- Analyzing the given options:
- Statement (B) is correct because the X-linked genes are indeed highly regulated to establish this balance.
- Statement (A) is also traditionally paired with (B) in competitive examinations because translational control and transcriptional modulation work together to fine-tune the final protein levels.
- Statement (C) is incorrect because X-chromosome inactivation does not occur in *Drosophila* (it is a mammalian trait).
- Statement (D) is incorrect because the Y chromosome in males is heterochromatic and gene-poor, and does not act as an X-chromosome.
Therefore, statements (A) and (B) only are correct.
Step 3: Final Answer:
The correct option is (A), and (B) only.
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