This set of Class 12 Biology Chapter 5 Multiple Choice Questions & Answers (MCQs) focuses on “Inheritance and Variation Principles – Mutation”.
1. Which of the following is incorrect with respect to mutation?
c) Change in chromosomes and genes
d) Leads to variation in DNA
Explanation: Mutations are not continuous. Instead, mutations are discontinuous variations in the genotype and phenotype of an organism. This is due to the changes in chromosomes and DNA. Mutations are sudden and they are a cause of the variation in DNA.
2. Which of the following is not a type of mutation?
a) Gene mutation
b) Chromosomal aberrations
c) Genomatic mutations
d) Colourful mutations
Explanation: Mutations are of three different types depending upon their cause and environment. The three types are:
i. Gene mutation
ii. Chromosomal aberrations
iii. Genomatic mutations
3. Which of the following is a classic example of point mutation?
b) Sickle cell anaemia
Explanation: Sickle cell anaemia is a classic example of point mutation. Point mutation generally means that when a single base pair of DNA changes, a gene mutation occurs that causes the alternation of DNA.
4. Which of the following is also known as the removal of one or more bases from the nucleotide chain?
Explanation: The removal of one or more bases from the nucleotide chain is also known as deletion. Deletion is a type of frame-shift mutation. If we add one or more bases in a nucleotide chain, then it is called insertion.
5. What is the substitution of a purine base with a pyrimidine base known as?
Explanation: The substitution of a purine base with a pyrimidine base or vice versa is known as transversion. This refers to the substitution mutation which is the replacement of one base by another.
6. Change in more than one nucleotide pair is known as a spontaneous mutation.
Explanation: No, change in more than one nucleotide pair is not called a spontaneous mutation, instead it is known as gross mutation. When gene mutations occur naturally and automatically due to any internal reasons, then it is called as spontaneous mutations.
7. Which of the following is not responsible for the formation of chromosomes?
d) Endoplasmic reticulum
Explanation: The endoplasmic reticulum is not responsible for the formation of chromosomes. Chromosomes are made up of proteins, DNA, and RNA. The loss or gain of a segment of DNA often causes the alternation of chromosomes.
8. Intercalary aberrations are a part of which of the following?
Explanation: Intercalary aberrations are a type of deletions where there is a loss of an intercalary segment of a chromosome due to its double break. Deletions result in the loss of some segments of chromosomes which further leads to mutation.
9. What does the given type of aberrations in the figure represent?
Explanation: The given figure represents the duplication aberrations where a part of the chromosome gets added so that a gene or a set of genes is duplicated or is represented twice.
10. How does deletion occur?
a) When a part of a chromosome is duplicated
b) When a part of a chromosome is left out
c) When a part of a chromosome is lost
d) When a part of a chromosome is translocated
Explanation: Deletions are a type of chromosomal aberrations where a part of a chromosome is lost. It is of two types-terminal and intercalary deletions. When the terminal segment of the chromosome is lost then it is known as terminal deletions and when an intercalary segment is lost then it is known as intercalary deletions.
11. What is translocation?
a) Shifting of part of chromosomes to the outside wall of nucleus
b) Shifting of a chromosome to another chromosome
c) Shifting of a part of a chromosome to another homologous chromosome
d) Shifting of a part of a chromosome to another non-homologous chromosome
Explanation: Translocation is the shifting of a part of a chromosome to another non-homologous chromosome. It results in the formation of new recombinant chromosomes as this induces faulty pairing of chromosomes during meiosis.
12. What is the full form of CML?
a) Chronic myopia lens
b) Chronic myelogenous leukaemia
c) Chronic muscle leukaemia
d) Cystic muscle leukaemia
Explanation: CML stands for Chronic myelogenous leukaemia. CML occurs due to the translocation of a segment of the long arm from chromosome 22 to chromosome 9. Chromosome 22 is also known as the Philadelphia chromosome.
13. Paracentric is a type of inversion involving centromere.
Explanation: Paracentric is not a type of inversion involving centromere. Instead, it is an inversion without involving centromere. Pericentric is a type of inversion which involves centromere.
14. Segmental changes of chromosome having an evolutionary significance, is of which of the following?
Explanation: An important class of translocation having evolutionary significance is known as segmental changes or reciprocal translocation. It involves the mutual exchange of chromosome segments between two non-homologous chromosomes.
15. In which of the following organisms, an inversion occurs frequently?
c) Honey bees
Explanation: Inversion occurs frequently in Drosophila as a result of X-ray radiation. Inversion is technically a type of chromosomal aberration where the linear order of genes changes by 180° through the rotation.
16. Genomatic mutation is of how many types?
Explanation: Genomatic mutations are of two types-
This kind of mutation involves the change in chromosome number that bring about visible threats on the phenotype.
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