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प्रश्न
In humans, males are heterogametic and females are homogametic. Explain. Are there any examples where males are homogametic and females heterogametic?
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उत्तर
The term homogametic and heterogametic refer to the organism depending upon whether all the gametes contain one type of sex chromosome (Homo = same) or two different types of sex chromosomes (Hetero = different) Humans show XX/XY type of sex determination i.e. Females contain 2 copies of X chromosome and males contain 1 X and 1 Y chromosome. Therefore, ova produced by females contain the same sex chromosome i.e. X. On the other hand, the sperms contain 2 different types of chromosomes i.e. 50% sperms have X and 50% have Y chromosome open from half the autosomes (Meiosis) Therefore, the sperms are different with respect to the composition of sex chromosome. In case of humans, females are considered to be homogametic while males are heterogametic. Yes, there are examples where males are homogametic and females are heterogametic. In some birds, the mode of sex determination is denoted by ZZ (males) and ZW (females).
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संबंधित प्रश्न
Answer the following questions related to sex determination in human beings:
i. What is sex chromosome?
ii. How many pairs of chromosomes are present in human beings?
iii. How is the sex of the human offspring determined?
iv. Draw a diagram depicting sex determination in man.
Name the species used in sericulture. Name the stages in the life cycle of a silk moth in cyclic form.
Explain the mechanism of 'sex determination' in birds. How does it differ from that of human beings?
Which of the following combinations of sex chromosomes produce a male child : XX or XY?
In a human, how many chromosmes are present in a skin cell?
The exchange of genetic material takes place in :
(a) vegetative reproduction
(b) asexual reproduction
(c) sexual reproduction
(d) budding
The number of pair(s) of sex chromosomes in the zygote of humans is ______.
Name two animals which have nineteen pairs of chromosomes.
Define the following:
Sex chromosomes
Choose the correct answer :
Human sex chromosomes are __________
In which livings, female decides the sex? Give two examples.
Explain the mechanism of sex determination in humans with a suitable chart.
ZW-ZZ system of sex determination occurs in
Brief about female heterogamety.
In human males all the chromosomes are paired perfectly except one. This/these unpaired chromosomes is/are ______.
- large chromosome
- small chromosome
- Y-chromosome
- X-chromosome
The number of pairs of sex chromosomes in the zygote of a human being is ______
A zygote which has an X-chromosome inherited from the father will develop into a
Some dinosaurs had feathers although they could not fly but birds have feathers that help them to fly. In the context of evolution this means that
The belief that the mother is completely responsible for the sex of the child is wrong because the child
Sex in honey bee is determined by ______.
The chromosomal constitution of a human female can be written as ______
Name the two types of gametes produced by men.
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.
A zygote which has Y chromosome inherited from the father will develop into a ______.
Twins are born to a family that lives next door to you. The twins are a boy and a girl. Which of the following must be true?
Which biological mechanism establishes whether an individual develops as male or female based on genetic or chromosomal factors?
Which term describes organisms where male and female reproductive organs are present in separate individuals?
