Principles of Inheritance and Variation MCQ

Ans: (a) check heterozygous in F1-generation

Explanation: Crossing of F1 which having dominant phenotype with the homozygous recessive parent is known as test cross and descendant of test cross is known as test cross progeny. Test cross was devised by Mendel to prove F1 obtained by crossing 2 pure breeding parents is heterozygous or hybrid. If the unknown genotype is homozygous, half of the descendants will show the dominant trait and the other half will show the recessive trait. Therefore, a test cross is used to check heterozygous in F1-generation. 

Ans: (b) Mirabilis

Explanation: Carl Correns reported the problem of incomplete dominance in Antirrhinum majus and Mirabilis Jalapa. In both these cases, there are two types of flower colours in pure state, which are red and white. When two types of plants are crossed, the hybrid of plants of F1-generation of pink colour flowers. The pink colour appears when we mix red and white colours with incomplete dominance.

Ques 3. Which of the following characteristics represent ‘Inheritance of blood groups in humans?

1. Dominance
2. Codominance
3. Multiple alleles
4. Incomplete dominance
5. Polygenic inheritance

a) 1, 4 and 5

b) 1, 2 and 3

c) 2, 3 and 4

d) 1, 3 and 5

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Ques 4. Independent assortment means 

1. Separation of characters of one parent
2. Non separation of characters of one parent
3. Combination of parental characters
4. Separation of parental characters

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Ques 5. Chromosomal theory of inheritance was proposed by

1. Sutton and Boveri
2. Bateson and Punnett
3. TH Morgan
4. Watson and Crick

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Ques 6. Which of the following will not result in the variation among siblings? 

1. Independent assortment of genes
2. Crossing over
3. Linkage
4. Mutation

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Ques 7. A pleiotropic gene

1. Controls a trait only in combination with another gene
2. Controls multiple sheets in an individual
3. Is expressed only in primitive plants
4. Is a gene involved evolved during Pliocene

Ans: (c) Controls multiple sheets in an individual

Explanation: The ability of a gene to have multiple phenotypic effects because it influences on the number of characters simultaneously is known as pleiotropy. The gene which has multiple phenotypic effects because of its capability to control expression of two or more characters is called pleiotropic gene. In humans, pleiotropy shows syndromes like Sickle cell anaemia and phenylketonuria.

Ans: (b) Phenylketonuria

Explanation: Phenylketonuria is the best example of fluid therapy. In Phenylketonuria, a single gene mutation that codes for enzyme phenylalanine hydroxylase can be seen. The manifest itself through phenotypic expression characterised by the mental retardation, reducing hair and skin pigmentation. It is a genetic disorder which is caused by slowing metabolism of amino acids phenylalanine in the cells of the body.

Ans: (a) Males are heterogametic

Explanation: In XX-XY types of determination of sex, males are considered as heterogametic. This is because males produce two types of sperms with X and Y. But the females are considered as homogametic, as they produce only single types of ova with X. In moths, ZO-ZZ type of determination of sex occurs where males are homogametic.

Ans: (b) Tt & Tt

Explanation: If we tend to make a cross between two tall plants which results in a few dwarf offspring, then the parental genotypes are Tt and Tt. This can be explained with the help of the following example:

The F1 plants of genotype, Tt are self-pollinated.

Phenotypic ratio: Tall: Dwarf if 3:1 

Genotypic ratio: Pure tall: Hybrid tall: Pure dwarf will be 1:2:1