Class 12 · Principles of Inheritance and Variation

Sex Determination in Chicks — NEET Biology

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📖 NCERT Source

Is the sperm or the egg responsible for the sex of the chicks?

NCERT Biology · Class 12 · Chapter 4 · Paragraph 73
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Which of the above statements are correct? S1: In the XY type of sex determination system, the male is homogametic and produces two types of gametes, namely X and Y. S2: Females in birds possess one Z and one W chromosome, making them responsible for determining the sex of their progeny. S3: Grasshoppers exhibit an XO type sex determination system where females have two X chromosomes and males have a single X chromosome. S4: In organisms with ZW sex determination, the total number of chromosomes is generally different in males and females. S5: An ovum carrying a Y-chromosome is formed in human females, which upon fertilization with an X-sperm, results in a male child.

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Correct answer: C S2 and S3

The question pertains to different sex determination mechanisms as described in NCERT Chapter 4. S1: In the XY type of sex determination (e.g., humans, Drosophila), males are heterogametic, producing two types of gametes (X and Y), while females are homogametic (XX), producing only X gametes. Thus, S1 is incorrect. S2: In birds, the ZW sex-determination system is observed where females are heterogametic (ZW) and males are homogametic (ZZ). Since females produce two types of gametes (Z and W), they determine the sex of the offspring. Thus, S2 is correct. S3: Grasshoppers are an example of the XO type of sex determination. In this system, females have a pair of X-chromosomes (XX), and males have only one X-chromosome (XO). Thus, S3 is correct. S4: NCERT states that in birds, which have ZW sex determination, the total number of chromosomes is the same in both males and females. Thus, S4 is incorrect. S5: Human females produce only one type of ovum, which carries an X-chromosome. The ovum never carries a Y-chromosome. Thus, S5 is incorrect. Therefore, only statements S2 and S3 are correct.

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Is the sperm or the egg responsible for the sex of the chicks?
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Principles of Inheritance and Variation, Class 12 NCERT Biology.

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