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प्रश्न
Explain the mechanism of sex determination in humans with a suitable chart.
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उत्तर
Sex Determination in human being:
- The chromosomal mechanism of sex determination in human beings is of the XX – XY type. The human diploid cell has 23 pairs of chromosomes.
- Out of these, 22 pairs of chromosomes are called autosomes, and one pair of chromosomes is called sex chromosomes that are responsible for the determination of sex.
- The human female has a pair of XX, homomorphic sex chromosomes while the male has XY, heteromorphic sex chromosomes.
- A human male has 44 autosomes + XY sex chromosomes, whereas a female has 44 autosomes + XX sex chromosomes.
- During gamete formation in males, the diploid germ cells in testis undergo spermatogenesis to produce two types of haploid sperms, 50% of sperms contain 22 autosomes and X chromosome while 50% of sperms contain 22 autosomes and the Y chromosome.
- In females, the diploid germ cells in ovaries undergo oogenesis to produce only one type of egg. All eggs contain 22 autosomes and an X chromosome.
- Thus human male is heterogametic and the female is homogametic.
- If sperm containing the X chromosome fertilizes the egg (ovum), the diploid zygote formed after fertilization grows into a female child.
- If sperm containing the Y chromosome fertilizes the egg, then the diploid zygote formed after fertilization grows into a male child.
- The sex of a child depends on the type of sperm fertilizing the egg and hence the father is responsible for the determination of the sex of the child and not the mother.
संबंधित प्रश्न
Write notes on sex determination in the unborn baby.
There are two sets of chromosomes in the zygote.
Fill in the following blank with suitable word :
Genes always work in ................ .
Does genetic combination of mother play a significant role in determining the sex of a new born baby?
- E is the gene for brown eye colour and e is the gene for blue eye colour. Which gene is (i) recessive, and (ii) dominant?
- Both father and mother have the genes Ee in their cells. What colour are their eyes?
- Which combination of genes in the zygote will produce children with blue eyes?
- Which combinations of genes in the zygote will produce children with brown eyes?
A couple with a newborn baby is troubled that the child does not resemble either of them. Suspecting that a mixup occurred at the hospital, they check the blood type of the infant. It is type O. Because the father is type A and the mother type B, they conclude that a mixup has definitely occurred. Are they correct? Give reason for your answer.
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?
Name any two genetic in humans.
________ shows haplo-diploid type of sex-determination.
Define the following:
Sex-linked characters
Complete the following sentence with appropriate word:
______are the alternative forms of a gene producing different effects.
Brief about female heterogamety.
Read the following statements and select the correct option.
i. If sperm containing Y chromosome fertilizes the ovum, then diploid zygote is formed that grows into a male child.
ii. If sperm containing X chromosome fertilizes ovum, then diploid zygote is formed, that grows into a female child.
Sex is determined in human beings ______.
Grasshopper is an example of XO type of sex determination in which the males have ______.
A zygote which has an X-chromosome inherited from the father will develop into a ______.
The maleness of a child is determined by ______
The two versions of a trait (character) which are brought in by the male and female gametes are situated on
How is the sex of a newborn individual determined in different species of animals? Give three examples to support your answer.
In the XX–XY sex determination system, if a female (XX) is fertilized by an X-bearing sperm, what is the resulting genotype of the offspring?
