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Questions
Mention the symptoms of Down syndrome.
Mention any six symptoms of disorder caused by trisomy of 21 chromosome.
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Solution
- Mental retardation, either mild or moderate.
- Skeletal underdevelopment.
- Unique facial characteristics, such as a small mouth, ears, and head.
- Usually round and flat, with an open mouth and a flat nose.
- Protruding tongue.
- The inner corner of the eyes is covered by an epicanthal skin fold.
- Slanting eyes.
- Broad palms with a single Palmer crease; flat hands with stubby fingers.
Notes
Students should refer to the question according to their questions and preferred marks.
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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)
Which autosomal trisomy is characterized by 'rocker-bottom' feet and overlapping fingers?
What is the karyotype of Turner's Syndrome?
What is the formula for trisomy?
Which sex chromosome aneuploidy affects males with an extra Y chromosome?
What type of structural abnormality is represented by a chromosomal segment that detaches and reattaches in reverse orientation?
Which structural chromosomal abnormality is exemplified by the Philadelphia chromosome associated with Chronic Myeloid Leukaemia?
What condition is characterized by the presence of the Philadelphia chromosome?
Which type of numerical abnormality is represented by a formula of 2n + 2?
What does the term 'hypogonadism' refer to in Klinefelter's Syndrome?
