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Principles Of Inheritance And Variation

Question
CBSEENBI12046931
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XO-chromosomal abnormality in human beings causes

  • Turner's syndrome

  • Down's syndrome

  • Klinefelter's syndrome

  • None of these

Solution

A.

Turner's syndrome

Turner's syndrome is characterised by the monosomy of XO type. It is characterized by a lack of ovaries and menstrual cycle. Affected women are sterile and lack secondary sexual characteristics, although the external genitalia are present. The syndrome is named after the US endocrinologist H. H. Turner (1892- 1970).

Down's syndrome is a congential form of mental retardation due to a chromosome defect in which there are three copies of chromosome no. 21 instead of the usual two (XXX). The affected individual has a short broad face and slanted eyes (as in the Mongolian races), short fingers, and weak muscles. It can be detected before birth by amniocentesis. It is named after the British physician John Down ( 1828- 96).

Klinefelter's syndrome is characterised by trisomy (XXY). These are male individuals, who are phenotypically fairly normal but have a fairly low sperm count and are therefore sterile.

Some More Questions From Principles of Inheritance and Variation Chapter

Give one example of genetic trait for each of the following in humans : (i) Lethality (ii) Multiple allelism.

What for symbols AA and Aa stand ?

Mention the phenomenon of pleiotropy by giving an example.

Name the plant that shows incomplete dominance in respect of the colour of its flower.

Write the genotypes of man with blood group A.

What is Mendel’s monohybrid phenotypic ratio ?

Write down Mendel’s dihybrid Phenotypic ratio 

Who were the rediscoverers of Mendelism ?

What are the real determinants of what an organism will become ?

What is the unique feature of F1 generation ?

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