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प्रश्न
How was it concluded that genes are located on chromosomes?
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उत्तर
Walter Sutton and Theodor Boveri studied the behaviour of chromosomes and genes during meiosis. They observed that the movement of the chromosome and that of the gene was similar. Based on this observation, thy proposed that genes are located on chromosomes.
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संबंधित प्रश्न
Klinefelters’ syndrome is characterized by a karyotype of ____________.
Pataus’ syndrome is also referred to as ____________.
Mention the symptoms of Down syndrome.
Define aneuploidy. How is it different from polyploidy? Describe the individuals having following chromosomal abnormalities.
- Trisomy of 21st Chromosome
- XXY
- XO
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The chromosome number is fixed for all normal organisms leading to species specification whereas any abnormality in the chromosome number of an organism results into abnormal individuals. For example, in humans, 46 is the fixed number of chromosomes both male and female. In males it is '44 + XY' and in females, it is '44 +XX'. Thus the human male is heterogametic, in other words produces two different types of gametes one with '22 + X' chromosomes and the other with '22 + Y' chromosomes respectively. Human female, on the other hand, is homo gametic i.e. produce only one type of gamete with '22 + X' chromosomes only. Sometimes an error may occur during the meiosis of the cell cycle, where the sister chromatids fail to segregate called nondisjunction, leading to the production of abnormal gametes with altered chromosome numbers. On fertilisation, such gametes develop into abnormal individuals. |
(a) State what is aneuploidy. (1)
(b) If during spermatogenesis, the chromatids of sex chromosomes fail to segregate during meiosis, write only the different types of gametes with altered chromosome numbers that could possibly be produced. (1)
(c) A normal human sperm (22 + Y) fertilises an ovum with karyotype '22 +XX'. Name the disorder the offspring thus produced would suffer from and write any two symptoms of the disorder. (2)
OR
(c) Name the best-known and most common autosomal aneuploid abnormality in humans and write any two symptoms. (2)
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:
Broad palm with single palm crease is visible in a person suffering from ______.
Which of the following karyotypes represents Down's Syndrome?
What is the karyotype of Patau Syndrome?
Which autosomal trisomy is characterized by 'rocker-bottom' feet and overlapping fingers?
What is the karyotype of Turner's Syndrome?
Which of the following is a characteristic feature of Turner's Syndrome?
Which type of structural chromosomal abnormality results in the permanent loss of a chromosomal segment?
How many total chromosomes does a human with Down's Syndrome have?
What is the term used to describe the loss of one or more chromosomes due to nondisjunction?
Which type of numerical abnormality is represented by a formula of 2n + 2?
Which trisomy is associated with kidney and lung defects in addition to cardiac abnormalities?
