Class 12: Principles of Inheritance and Variation MCQs: Inheritance is the term given to the process by which characters are passed from parents to offspring which forms the basis of heredity. Heredity is the process of passing down genetic traits from parents to offspring. The degree of difference in characters between a parent and offspring is called variation. All these are studied under genetics which deals with the study of inheritance and variation of characters passed from parents to offspring. The first proper documented study of this inheritance and variation was done by G.J. Mendel which is why he is considered the father of genetics.
Class 12 Biology Principles of Inheritance and Variation MCQ with Answer
Q1. Which of the following statements is the most appropriate for sickle cell anaemia?
- It cannot be treated with iron supplements.
- It is a molecular disease.
- It confers resistance to acquiring malaria.
- All of the above.
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Ans: 4. All of the above.
Sickle cell anaemia: It is molecular disease, autosomal recessive disorder, an example of pleitropy, it cannot be treated with iron
supplements and it confers resistance to acquiring malaria.
Q2. From a cross AABb × aaBb, the genotypes AaBB : AaBb : Aabb will be obtained in the ratio:
- 1 : 1 : 2
- 1 : 2 : 1
- 2 : 1 : 1
- 2 : 1 : 2
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Ans: 2. 1 : 2 : 1
Q3. If a genetic disease is transferred from a phenotypically normal but carrier female to only some of the male
progeny, the disease is:
- Autosomal dominant.
- Autosomal recessive.
- Sex-linked dominant.
- Sex-linked recessive.
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Ans: 4. Sex-linked recessive.
Sex-linked recessive disease- A genetic disease is transferred from a phenotypically normal but carrier female to only some of the
male progeny.
Q4. If a haemophilic woman marries a normal man:
- All their children will be normal.
- All their sons will be haemophilic.
- All their daughters will be haemophilic.
- 50% sons and 50% daughters will be haemophilic.
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Ans: 2. All their sons will be haemophilic.
Q5. A woman with normal vision has a colorblind father. She marries a colourblind man. What proportion of their
children will be colourblind?
- 0%
- 25%
- 50%
- 100%
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Ans: 3. 50%
Q6. Two genes ‘A’ and ‘B’ are linked. In a dihybrid cross involving these two genes, the F heterozygote is crossed with
homozygous recessive parental type (aa bb). What would be the ratio of offspring in the next generation?
- 1 : 1 : 1 : 1.
- 9 : 3 : 3 : 1.
- 3 : 1.
- 1 : 1.
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Ans: 4. 1 : 1.
Q7. In the F2 generation of a Mendelian dihybrid cross the number of phenotypes and genotypes are:
- Phenotypes – 4; genotypes – 16.
- Phenotypes – 9; genotypes – 4.
- Phenotypes – 4; genotypes – 8.
- Phenotypes – 4; genotypes – 9.
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Ans: 4. Phenotypes – 4; genotypes – 9.
Q8. The inheritance pattern of a gene over generations among humans is studied by the pedigree analysis. Character
studied in the pedigree analysis is equivalent to:
- Quantitative trait.
- Mendelian trait.
- Polygenic trait.
- Maternal trait.
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Ans: 2. Mendelian trait.
The pattern of inheritance of Mendelian disorders can be traced through pedigree analysis.
Q9. A Across between two tall plants resulted in offspring having few dwarf plants. What would be the genotypes of
both the parents?
- TT and Tt.
- Tt and Tt.
- TT and TT.
- Tt and tt
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Ans: 2. Tt and Tt.
Q10. In a certain taxon of insects some have 17 chromosomes and the others have 18 chromosomes. The 17 and 18
chromosome-bearing organisms are:
- Males and females, respectively.
- Females and males, respectively.
- All males.
- All females.
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Ans: 1. Males and females, respectively.
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Ans: 3. Haemophilia and red-green colour blindness.
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Ans: 2. It is an autosomal recessive trait.
Q13. All genes located on the same chromosome:
- Form different groups depending upon their relative distance.
- Form one linkage group.
- Will not from any linkage groups.
- Form interactive groups that affect the phenotype.
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Ans: 1. Form one linkage group.
Q14. ZZ/ ZW type of sex determination is seen in:
- Platypus.
- Snails.
- Cockroach.
- Peacock.
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Ans: 4. Peacock.
This type of sex determination is seen in birds. The female has a ZW combination while the male has ZZ combination.
Q15. Mendel’s Law of independent assortment holds good for genes situated on the:
- Non-homologous chromosomes.
- Homologous chromosomes.
- Extra nuclear genetic element.
- Same chromosome.
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Ans: 2. Homologous chromosomes
Q16. Person having genotype IA IB would show the blood group as AB. This is because of:
- Pleiotropy.
- Co-dominance.
- Segregation.
- Incomplete dominance
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Ans: 2. Co-dominance.
Q17. In sickle cell anaemia glutamic acid is replaced by valine. Which one of the following triplets codes for valine?
- G. G. G.
- A. A. G.
- G. A. A.
- G. U. G.
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Ans: 4. G. U. G.
Q18. Distance between the genes and percentage of recombination shows:
- A direct relationship.
- An inverse relationship.
- A parallel relationship.
- No relationship
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Ans: 1. A direct relationship.
Q19. Which of the following will not result in variations among siblings?
- Independent assortment of genes.
- Crossing over.
- Linkage.
- Mutation.
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Ans: 3. Linkage.
Linkage happens in all cases whenever two genes are located on the same chromosome and are close to each other. Thus, linkage has
nothing to do with variation.
Q20. For question two statements are given-one labelled Assertion and the other labelled Reason. Select the correct
answer to these questions from the codes (a), (b), (c) and (d) as given below.
- Both assertion and reason are true and reason is the correct explanation of assertion.
- Both assertion and reason are true but reason is not the correct explanation of assertion.
- Assertion is true but reason is false.
- Both assertion and reason are false.
Assertion: Codominant alleles lack dominant recessive relationship.
Reason: Codominant alleles show incomplete dominance.
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Ans: 3. Assertion is true but reason is false