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CBSE 12th Standard Biology Subject Principles of Inheritance and Variation Ncert Exemplar 2 Marks Questions 2021

Published on: 25/05/2021

QB365 Provides the updated NCERT Examplar Questions for Class 12 Biology, and also provide the detail solution for each and every ncert examplar questions , QB365 will give all kind of study materials will help to get more marks

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Questions:

Generic 2

5 x 2 = 10

A woman of 47 years delivered an abnormal child with a flattened nasal bridge and mouth partially open with a large protruding tongue. Name this genetic abnormality. What causes this condition?

Linkage and crossing over of genes are alternatives of each other. Justify with the help of an example.

The pedigree chart given below shows a particular trait which is absent in parents but present in the next generation irrespective of sexes.
Draw your conclusion on the basis of the pedigree.

In our society, a woman is often blamed for not bearing a male child.Do you think it is right? Justify

If a father and son are both defective in red-green colour vision, is it likely that the son inherited the trait from his father? Comment.

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Answers Key:

Generic 2

5 x 2 = 10

(i) This genetic disorder is called Down's syndrome.
(ii) This condition is caused due to trisomy of chromosome number 21 (an additional copy of chromosome 21).

Linkage is the tendency of certain loci or alleles (genes) to be inherited together while, crossing over is the segregation of genes, e.g.the genes on a chromosome either follow linkage path or cross over, to form the gametes during gametogenesis in human.

It is an autosomal recessive trait that is not found in the parents, but has appeared irrespective of sex in the offspring. It this case, both the parents are heterozygous for the trait.

In our society a woman is often blamed for not bearing a male child.It is wrong because sex of child is determined by gametes formed by man who is heterogametic for sex chromosomes whereas woman is homogametic.

- No, the son never inherits colour blindness from his father.

- The gene for colour-blindness is present on the x-chromosome, but a son receives Y-chromosome from his father.

- Since a male receives the X-chromosome from his mother, he ihherits the disease from his mother only.