Sex Determination in Birds — NEET Biology
📚 Practice ConceptIn order to have a distinction with the mechanism of sex determination described earlier, the two different sex chromosomes of a female bird has been designated to be the Z and W chromosomes. In these organisms the females have one Z and one W chromosome, whereas males have a pair of Z-chromosomes besides the autosomes.
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.
View solution & NCERT explanation
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.
What does NCERT say about order to have distinction?
Has this concept appeared in NEET?
Which chapter is this from?
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