Class 12 Biology MCQ Chapter 5 Principles of Inheritance and Variation
Unlock the fundamentals of genetics with our Class 12 Biology MCQ Chapter 5 Principles of Inheritance and Variation English Medium collection. This article provides a rich set of multiple-choice questions (MCQs) with answers, specially designed for AHSEC Higher Secondary students who want to strengthen their understanding of heredity and genetic variation.
The chapter Principles of Inheritance and Variation introduces students to the laws of inheritance and the mechanisms through which traits are passed from one generation to the next. Important topics covered include Mendel’s experiments, inheritance patterns, dominance, segregation, independent assortment, chromosomal theory of inheritance, sex determination, mutations, genetic disorders, and sources of variation. These concepts form the foundation of modern genetics and are among the most important topics in Class 12 Biology.
All MCQs are prepared according to the latest AHSEC syllabus and examination pattern, ensuring that students receive relevant and exam-oriented practice. Solving these objective questions regularly will help improve conceptual clarity, analytical skills, and confidence in tackling board examination questions.
Whether you are preparing for classroom assessments, model tests, or the AHSEC Higher Secondary Final Examination, these Chapter 5 MCQ solutions will help you revise important concepts effectively and achieve better academic results.
Unit VII: Genetics and Evolution
Principles of Inheritance and Variation
VSA & MCQ
I. Very Short Question-Answers
Q. Who is known as the Father of Genetics?
Ans: Gregor Johann Mendel.
Q. Which plant was selected by Mendel for his experiments?
Ans: Garden pea (Pisum sativum).
Q. What is heredity?
Ans: Heredity is the transmission of characters from parents to offspring.
Q. What is variation?
Ans: Variation refers to differences among individuals of the same species.
Q. What is a gene?
Ans: A gene is the unit of heredity controlling a specific character.
Q. Define allele.
Ans: Alleles are alternative forms of the same gene.
Q. What is a dominant trait?
Ans: A dominant trait is expressed in both homozygous and heterozygous conditions.
Q. What is a recessive trait?
Ans: A recessive trait is expressed only in homozygous condition.
Q. What is genotype?
Ans: Genotype is the genetic constitution of an organism.
Q. What is phenotype?
Ans: Phenotype is the observable character of an organism.
Q. What is homozygous condition?
Ans: It is the condition in which both alleles are similar.
Q. What is heterozygous condition?
Ans: It is the condition in which both alleles are different.
Q. State Mendel’s law of segregation.
Ans: The two alleles of a gene separate during gamete formation.
Q. What is monohybrid cross?
Ans: A cross involving one pair of contrasting characters.
Q. What is dihybrid cross?
Ans: A cross involving two pairs of contrasting characters.
Q. What is incomplete dominance?
Ans: Incomplete dominance is a condition in which neither allele is completely dominant.
Q. Give one example of incomplete dominance.
Ans: Snapdragon flower colour.
Q. What is codominance?
Ans: Codominance is the expression of both alleles equally in heterozygous condition.
Q. Give one example of codominance.
Ans: ABO blood group in humans.
Q. What are multiple alleles?
Ans: More than two alternative forms of a gene are called multiple alleles.
Q. What is pleiotropy?
Ans: Pleiotropy is the phenomenon in which one gene controls multiple traits.
Q. What is linkage?
Ans: Linkage is the tendency of genes present on the same chromosome to be inherited together.
Q. What is crossing over?
Ans: Crossing over is the exchange of genetic material between homologous chromosomes.
Q. Who discovered linkage?
Ans: Thomas Hunt Morgan.
Q. What are sex chromosomes?
Ans: Chromosomes responsible for determination of sex.
Q. Which chromosomes determine maleness in humans?
Ans: XY chromosomes.
Q. What is haemophilia?
Ans: Haemophilia is a sex-linked recessive disorder causing defective blood clotting.
Q. What is colour blindness?
Ans: Colour blindness is the inability to distinguish certain colours.
Q. What is mutation?
Ans: Mutation is a sudden heritable change in genetic material.
Q. What is Turner’s syndrome?
Ans: Turner’s syndrome is a chromosomal disorder in females with 45 chromosomes.
II. Multiple Choice Questions (MCQs)
Q. Father of Genetics is:
(a) Charles Darwin
(b) Gregor Johann Mendel
(c) Thomas Hunt Morgan
(d) Hugo de Vries
Ans: (b) Gregor Johann Mendel
Q. Mendel performed experiments on:
(a) Maize
(b) Pea plant
(c) Wheat
(d) Mango
Ans: (b) Pea plant
Q. The unit of heredity is:
(a) Chromosome
(b) Cell
(c) Gene
(d) Nucleus
Ans: (c) Gene
Q. The observable character of an organism is called:
(a) Genotype
(b) Allele
(c) Phenotype
(d) Mutation
Ans: (c) Phenotype
Q. TT represents:
(a) Heterozygous
(b) Homozygous dominant
(c) Homozygous recessive
(d) Hybrid
Ans: (b) Homozygous dominant
Q. Tt represents:
(a) Homozygous dominant
(b) Homozygous recessive
(c) Heterozygous
(d) Pure line
Ans: (c) Heterozygous
Q. Mendel’s law of segregation is also called:
(a) Law of purity of gametes
(b) Law of linkage
(c) Law of dominance
(d) Law of mutation
Ans: (a) Law of purity of gametes
Q. A monohybrid cross involves:
(a) One trait
(b) Two traits
(c) Three traits
(d) Four traits
Ans: (a) One trait
Q. Phenotypic ratio in monohybrid cross is:
(a) 1 : 2 : 1
(b) 9 : 3 : 3 : 1
(c) 3 : 1
(d) 1 : 1
Ans: (c) 3 : 1
Q. Phenotypic ratio in Mendel’s dihybrid cross is:
(a) 3 : 1
(b) 1 : 2 : 1
(c) 9 : 3 : 3 : 1
(d) 1 : 1
Ans: (c) 9 : 3 : 3 : 1
Q. Incomplete dominance was first observed in:
(a) Pea
(b) Snapdragon
(c) Rose
(d) Hibiscus
Ans: (b) Snapdragon
Q. ABO blood group is an example of:
(a) Incomplete dominance
(b) Codominance
(c) Linkage
(d) Mutation
Ans: (b) Codominance
Q. IA and IB are:
(a) Dominant alleles
(b) Recessive alleles
(c) Codominant alleles
(d) Lethal alleles
Ans: (c) Codominant alleles
Q. Linkage was discovered by:
(a) Mendel
(b) Darwin
(c) Morgan
(d) Lamarck
Ans: (c) Morgan
Q. Crossing over occurs during:
(a) Prophase-I
(b) Metaphase-I
(c) Anaphase-I
(d) Telophase-I
Ans: (a) Prophase-I
Q. Chromosomes responsible for sex determination are:
(a) Autosomes
(b) Allosomes
(c) Chromatids
(d) Centromeres
Ans: (b) Allosomes
Q. Human male has sex chromosomes:
(a) XX
(b) XY
(c) XO
(d) YY
Ans: (b) XY
Q. Human female has sex chromosomes:
(a) XY
(b) XO
(c) XX
(d) YY
Ans: (c) XX
Q. Haemophilia is a:
(a) Autosomal disorder
(b) Sex-linked disorder
(c) Nutritional disorder
(d) Metabolic disorder
Ans: (b) Sex-linked disorder
Q. Colour blindness is:
(a) Dominant disorder
(b) Sex-linked recessive disorder
(c) Bacterial disease
(d) Viral disease
Ans: (b) Sex-linked recessive disorder
Q. Sudden heritable change is called:
(a) Variation
(b) Mutation
(c) Linkage
(d) Evolution
Ans: (b) Mutation
Q. Down’s syndrome is caused by:
(a) Monosomy
(b) Trisomy of chromosome 21
(c) XO condition
(d) XXY condition
Ans: (b) Trisomy of chromosome 21
Q. Turner’s syndrome has chromosome number:
(a) 46
(b) 47
(c) 45
(d) 44
Ans: (c) 45
Q. Klinefelter’s syndrome is represented by:
(a) XO
(b) XXY
(c) XXX
(d) YY
Ans: (b) XXY
Q. Test cross is used to determine:
(a) Dominant character
(b) Recessive character
(c) Genotype of dominant individual
(d) Mutation
Ans: (c) Genotype of dominant individual
Q. The cross between F1 individual and recessive parent is:
(a) Back cross
(b) Test cross
(c) Dihybrid cross
(d) Monohybrid cross
Ans: (b) Test cross
Q. Pleiotropy means:
(a) One gene controls many traits
(b) Many genes control one trait
(c) One chromosome controls one trait
(d) Mutation in genes
Ans: (a) One gene controls many traits
Q. Blood group O has genotype:
(a) IAIA
(b) IAIB
(c) ii
(d) IBIB
Ans: (c) ii
Q. The physical appearance of genotype is:
(a) Mutation
(b) Phenotype
(c) Linkage
(d) Allele
Ans: (b) Phenotype
Q. Mendel’s law of independent assortment applies to genes located on:
(a) Same chromosome
(b) Different chromosomes
(c) Centromere
(d) Chromatids
Ans: (b) Different chromosomes
Q. Assertion (A): Mendel is known as the Father of Genetics.
Reason (R): Mendel explained the basic principles of inheritance through pea plant experiments.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (b)
Q. Assertion (A): In incomplete dominance, both alleles express equally.
Reason (R): Snapdragon flower shows intermediate phenotype.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (d)
Q. Assertion (A): ABO blood group system is an example of codominance.
Reason (R): IA and IB alleles express equally in AB blood group.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (a)
Q. Assertion (A): Haemophilia is more common in males.
Reason (R): Haemophilia is an X-linked recessive disorder.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (b)
Q. Assertion (A): Crossing over increases genetic variation.
Reason (R): Crossing over involves exchange of genetic material between homologous chromosomes.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (a)
Q. Assertion (A): Turner’s syndrome occurs due to trisomy.
Reason (R): Turner’s syndrome individuals have 45 chromosomes.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (d)
Q. Assertion (A): Genes located on the same chromosome show linkage.
Reason (R): Linked genes tend to inherit together.
(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.
Ans: (c)
