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प्रश्न
Explain the mechanism of 'sex determination' in birds. How does it differ from that of human beings?
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उत्तर
- The sex chromosomes in birds are determined as Z and W. The male is homomorphic (ZZ) and the female is heteromorphic (ZW).
- W chromosome carries female sex-determining genes and duplication of Z chromosome indicates male sex.
- So, in case of chicks, the sex is determined by the egg and not by the sperms.
- The difference between sex mechanisms of humans.
- birds is that the male is homomorphic (ZZ) and the female is heteromorphic (ZW) in birds, whereas the male is heteromorphic (XY) and female is homomorphic (XX) in humans.
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संबंधित प्रश्न
In a human, how many chromosmes are present in a sperm in the testes?
Both father and mother have the genes Ee in their cells. What colour are their eyes?
The person A has only B chromosomes in all its gametes. On the other hand, another person C has chromosome D in half of gametes and chromosome E in the other half of gametes. When chromosomes B and D combine during fertilisation, a female zygote results. On the other hand, combination of B and E chromosomes produces a male zygote.
(a) What are chromosomes (i) B (ii) D, and (iii) E?
(b) Out of B, D and E, which two chromosomes are of the same type?
(c) Which chromosome is smaller in size?
(d) What is the general name of chromosomes such as B and E?
(e) Out of the two persons A and C, which one is (i) male, and (ii) female?
Distinguish between heterogametic and homogametic sex determination systems.
A man with blood group A marries a woman having blood group O. What will be the blood group of the child?
Which of the following determines the sex of a child?
The maleness of a child is determined by
Which of the following statements is not true with respect to variation?
All human chromosomes ate not paired. Most human chromosomes have a maternal and a paternal copy, and we have 22 such pairs. But one pair called the sex chromosomes, is odd in not always being a perfect pair. Women have a perfect pair of sex chromosomes. But men have a mismatched pair in which one is normal sized while the other is a short one.
(a) In humans, how many chromosomes are present in a Zygote and in each gamete?
(b) A few reptiles rely entirely on environmental cues for sex determination. Comment.
(c) "The sex of a child is a matter of chance and none of the parents are considered to be responsible for it." Justify it through flow chart only.
OR
(c) Why do all the gametes formed in human females have an X chromosome?
What is the probability of a girl or a boy being born into a family? Justify your answer.
