CBSE Class 12 Biology Principles Of Inheritance And Variation Minds Map

Important Questions for NCERT Class 12 Biology Principles of Inheritance and Variation

Ques. What is the genetic disorder in which an individual has an overall masculine development, gynaecomastia and is sterile?
(a) Down’s syndrome
(b) Turner’s syndrome
(c) Klinefelter’s syndrome
(d) Edward syndrome 

Answer: C

Ques. A woman has an X-linked condition on one of her X chromosomes. This chromosome can be inherited by
(a) only daughters
(b) only sons
(c) only grandchildren
(d) both sons and daughters. 

Answer: D

Ques. Thalassemia and sickle cell anaemia are caused due to a problem in globin molecule synthesis. Select the correct statement.
(a) Both are due to a quantitative defect in globin chain synthesis.
(b) Thalassemia is due to less synthesis of globin molecules.
(c) Sickle cell anaemia is due to a quantitative problem of globin molecules.
(d) Both are due to a qualitative defect in globin chain synthesis. 

Answer: B

Ques. A disease caused by an autosomal primary nondisjunction is
(a) Klinefelter’s syndrome
(b) Turner’s syndrome
(c) Sickle cell anaemia
(d) Down’s syndrome. 

Answer: D

Ques. If a colour-blind man marries a woman who is homozygous for normal colour vision, the probability of their son being colour-blind is
(a) 0 (b) 0.5
(c) 0.75 (d) 1.

Answer: A

Ques. Pick out the correct statements.
(1) Haemophilia is a sex-linked recessive disease.
(2) Down’s syndrome is due to aneuploidy.
(3) Phenylketonuria is an autosomal recessive gene disorder.
(4) Sickle cell anaemia is an X-linked recessive gene disorder.
(a) (1), (3) and (4) are correct.
(b) (1), (2) and (3) are correct.
(c) (1) and (4) are correct.
(d) (2) and (4) are correct. 

Answer: B

Ques. Which of the following most appropriately describes haemophilia?
(a) Chromosomal disorder
(b) Dominant gene disorder
(c) Recessive gene disorder
(d) X-linked recessive gene disorder

Answer: D

Ques. A colour blind man marries a woman with normal sight who has no history of colour blindness in her family. What is the probability of their grandson being colour blind ?
(a) Nil (b) 0.25
(c) 0.5 (d) 1

Answer: B

Ques. An abnormal human baby with ‘XXX’ sex chromosomes was born due to
(a) fusion of two ova and one sperm
(b) fusion of two sperms and one ovum
(c) formation of abnormal sperms in the father
(d) formation of abnormal ova in the mother.

Answer: D

Ques. A man whose father was colour blind marries a woman who had a colour blind mother and normal father. What percentage of male children of this couple will be colour blind?
(a) 25% (b) 0%
(c) 50% (d) 75% 

Answer: C

Ques. A human female with Turner’s syndrome
(a) has 45 chromosomes with XO
(b) has one additional X chromosome
(c) exhibits male characters
(d) is able to produce children with normal husband. 

Answer: A

Ques. Select the incorrect statement with regard to haemophilia.
(a) It is a dominant disease.
(b) A single protein involved in the clotting of blood is affected.
(c) It is a sex-linked disease.
(d) It is a recessive disease. 

Answer: A

Ques. If both parents are carriers for thalassaemia, which is an autosomal recessive disorder, what are the chances of pregnancy resulting in an affected child?
(a) 25% (b) 100%
(c) No chance (d) 50% 

Answer: A

Ques. Which one is the incorrect statement with regard to the importance of pedigree analysis?
(a) It confirms that DNA is the carrier of genetic information.
(b) It helps to understand whether the trait in question is dominant or recessive.
(c) It confirms that the trait is linked to one of the autosome.
(d) It helps to trace the inheritance of a specific trait. 

Answer: A

Ques. Down’s syndrome in humans is due to
(a) three ‘X’ chromosomes
(b) three copies of chromosome 21
(c) monosomy
(d) two ‘Y’ chromosomes. 

Answer: B

Ques. A normal-visioned man whose father was colourblind, marries a woman whose father was also colour-blind. They have their first child as a daughter. What are the chances that this child would be colour-blind?
(a) 100% (b) Zero percent
(c) 25% (d) 50%

Answer: B

Ques. Which one of the following conditions correctly describes the manner of determining the sex?
(a) Homozygous sex chromosomes (ZZ) determine female sex in birds.
(b) XO type of sex chromosomes determine male sex in grasshopper.
(c) XO condition in humans as found in Turner’s syndrome, determines female sex.
(d) Homozygous sex chromosomes (XX) produce male in Drosophila.

Answer: B

Ques. Select the incorrect statement from the following.
(a) Galactosemia is an inborn error of metabolism.
(b) Small population size results in random genetic drift in a population.
(c) Baldness is a sex-limited trait.
(d) Linkage is an exception to the principle of independent assortment in heredity. 

Answer: C

Ques. Sickle-cell anaemia is
(a) caused by substitution of valine by glutamic acid in the beta globin chain of haemoglobin
(b) caused by a change in a single base pair of DNA
(c) characterized by elongated sickle like RBCs with a nucleus
(d) an autosomal linked dominant trait.

Answer: B