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प्रश्न
What is Down’s syndrome? Give its symptoms and cause. Why is it that the chances of having a child with Down’s syndrome increases if the age of the mother exceeds forty years?
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उत्तर
Down’s syndrome is a human genetic disorder caused due to trisomy of chromosome no. 21. Such individuals are aneuploid and have 47 chromosomes. (2n + 1) The symptoms include mental retardation, growth abnormalities, constantly open mouth, dwarfness etc. The reason for the disorder is the non-disjunction (failure to separate) of homologous chromosome of pair 21 during meiotic division in the ovum. The chances of having a child with Down’s syndrome increase with the age of the mother (+ 40) because ova are present in females. since their birth and therefore older cells are more prone to chromosomal non-disjunction because of various physico-chemical exposures during the mother’s life-time.
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संबंधित प्रश्न
Females with Turners’ syndrome have
How was it concluded that genes are located on chromosomes?
Define aneuploidy. How is it different from polyploidy? Describe the individuals having following chromosomal abnormalities.
- Trisomy of 21st Chromosome
- XXY
- XO
Match List I with List II.
| List I | List II | ||
| A. | Down’s syndrome | I. | 11th chromosome |
| B. | α-Thalassemia | II. | ‘X’ chromosome |
| C. | β-Thalassemia | III. | 21st chromosome |
| D. | Klinefelter’s syndrome | IV. | 16th chromosome |
Choose the correct answer from the options given below:
Which of the following statements are correct about Klinefelter’s Syndrome?
- This disorder was first described by Langdon Down (1866).
- Such an individual has overall masculine development. However, the feminine development is also expressed.
- The affected individual is short statured.
- Physical, psychomotor and mental development is retarded.
- Such individuals are sterile.
Choose the correct answer from the options given below:
What is the karyotype of Patau Syndrome?
What is the karyotype of Turner's Syndrome?
Which of the following is a characteristic feature of Turner's Syndrome?
Which type of aneuploidy results in a total of 45 chromosomes?
What is the formula for trisomy?
Which sex chromosome aneuploidy affects males with an extra Y chromosome?
Which structural chromosomal abnormality involves a chromosomal segment being copied and repeated?
Which structural chromosomal abnormality is exemplified by the Philadelphia chromosome associated with Chronic Myeloid Leukaemia?
What is the term used to describe the loss of one or more chromosomes due to nondisjunction?
In which parent does nondisjunction most commonly occur to cause Down's Syndrome?
What is the incidence of Edwards Syndrome in relation to other trisomies?
Which type of numerical abnormality is represented by a formula of 2n + 2?
What does the term 'hypogonadism' refer to in Klinefelter's Syndrome?
