Sure! Here's a set of 50 multiple-choice questions (MCQs) on the chapter Principles of Inheritance and Variation for Class 12 Biology, along with the answer key at the end.
MCQs: Principles of Inheritance and Variation
-
Who is known as the father of genetics?
A) Charles Darwin
B) Gregor Mendel
C) Hugo de Vries
D) Watson -
Mendel’s work was rediscovered by:
A) Morgan
B) de Vries, Correns, and von Tschermak
C) Watson and Crick
D) Darwin -
Which plant did Mendel use for his experiments?
A) Pea
B) Bean
C) Maize
D) Wheat -
In a monohybrid cross, the F2 phenotypic ratio is:
A) 1:2:1
B) 3:1
C) 9:3:3:1
D) 2:1 -
In a dihybrid cross, the F2 phenotypic ratio is:
A) 3:1
B) 9:3:3:1
C) 1:2:1
D) 1:1 -
A gene pair that masks the expression of another gene pair is called:
A) Codominant
B) Epistatic
C) Hypostatic
D) Recessive -
Alleles are:
A) Homologous chromosomes
B) Alternative forms of a gene
C) Sister chromatids
D) Sex chromosomes -
When both alleles express equally in a heterozygous condition, it is called:
A) Incomplete dominance
B) Codominance
C) Multiple alleles
D) Polygenic inheritance -
AB blood group is an example of:
A) Codominance
B) Incomplete dominance
C) Multiple allelism
D) Both A and C 
-
Which of the following is not a Mendelian disorder?
A) Haemophilia
B) Colour blindness
C) Sickle-cell anaemia
D) Phenylketonuria -
Which law states that alleles segregate during gamete formation?
A) Law of independent assortment
B) Law of segregation
C) Law of dominance
D) Law of linkage -
The term “gene” was coined by:
A) Mendel
B) Morgan
C) Johansen
D) Watson -
In Mendel’s experiments, the tall trait is:
A) Recessive
B) Dominant
C) Codominant
D) Neutral -
The chromosomal theory of inheritance was proposed by:
A) Mendel
B) Sutton and Boveri
C) Morgan
D) Watson and Crick -
A condition in which a single gene influences multiple traits is called:
A) Codominance
B) Epistasis
C) Pleiotropy
D) Polygenic inheritance -
A test cross is used to determine:
A) Dominance
B) Linkage
C) Genotype of an individual
D) Mutation -
Genes located close to each other on the same chromosome are said to be:
A) Linked
B) Recombined
C) Codominant
D) Mutated -
Who discovered sex-linked inheritance in Drosophila?
A) Sutton
B) Boveri
C) Morgan
D) Mendel -
In humans, sex is determined by:
A) Autosomes
B) X-chromosomes
C) Y-chromosome
D) Hormones -
XXY in humans causes:
A) Down’s syndrome
B) Klinefelter’s syndrome
C) Turner’s syndrome
D) Super female -
A man with blood group A marries a woman with blood group B. Their child could be:
A) A or B only
B) AB only
C) Any blood group
D) O only -
The genotype of a recessive individual is:
A) Homozygous dominant
B) Homozygous recessive
C) Heterozygous
D) None -
A carrier female for haemophilia marries a normal male. The probability of their son having haemophilia is:
A) 25%
B) 50%
C) 75%
D) 100% -
Which of the following is a sex-linked recessive disorder?
A) Down syndrome
B) Sickle cell anaemia
C) Colour blindness
D) Phenylketonuria -
Phenylketonuria is due to the absence of enzyme:
A) Lactase
B) Tyrosinase
C) Phenylalanine hydroxylase
D) Amylase -
A woman with blood group AB can have a child with blood group O:
A) Always
B) Never
C) Sometimes
D) Rarely -
The gene which determines maleness in humans is located on:
A) X chromosome
B) Y chromosome
C) Autosomes
D) Mitochondria -
A pure tall pea plant crossed with a pure dwarf gives F1 as:
A) All tall
B) All dwarf
C) Tall and dwarf
D) Medium height -
In incomplete dominance, the F1 phenotype is:
A) Dominant
B) Recessive
C) Intermediate
D) Any of the above -
Down syndrome results from:
A) Trisomy 21
B) Monosomy X
C) XXY
D) Deletion of chromosome 5 -
The physical appearance of an individual is known as:
A) Genotype
B) Phenotype
C) Karyotype
D) Zygote -
Which of the following is a qualitative trait?
A) Height
B) Skin colour
C) Blood group
D) Weight -
What is the probability of a child being a boy?
A) 100%
B) 75%
C) 50%
D) 25% -
The chance of haemophilia passing from a carrier mother to son is:
A) 0%
B) 25%
C) 50%
D) 100% -
Gregor Mendel performed his experiments in:
A) Austria
B) Germany
C) England
D) France -
Morgan’s work with Drosophila proved the concept of:
A) Mutation
B) Sex-linked inheritance
C) Polygenic inheritance
D) Incomplete dominance -
The number of chromosomes in Drosophila is:
A) 4 pairs
B) 2 pairs
C) 6 pairs
D) 8 pairs -
Multiple alleles are best illustrated by:
A) Height
B) Blood groups
C) Eye colour
D) Haemophilia -
The expected ratio of monohybrid test cross is:
A) 1:1
B) 3:1
C) 9:3:3:1
D) 1:2:1 -
Linkage reduces:
A) Crossing over
B) Mutation
C) Variation
D) Gene expression -
Who coined the term linkage?
A) Mendel
B) Morgan
C) Sutton
D) Bateson -
Which one is an autosomal recessive disorder?
A) Colour blindness
B) Haemophilia
C) Sickle-cell anaemia
D) Klinefelter's syndrome -
Which of the following is a genetic disorder caused by a recessive allele?
A) Diabetes
B) Haemophilia
C) Obesity
D) Down syndrome -
Which is not true about Mendel's laws?
A) They apply to all organisms
B) They explain chromosomal inheritance
C) They are based on probability
D) They work in polygenic traits -
The term “genotype” refers to:
A) Physical appearance
B) Genetic makeup
C) Blood type
D) Hybrid -
Sickle cell disease is due to mutation in:
A) Albumin
B) Globulin
C) Haemoglobin
D) Myoglobin -
In codominance, the phenotype shows:
A) One dominant trait
B) Both traits equally
C) Intermediate trait
D) Recessive trait -
Genes for colour blindness are located on:
A) X chromosome
B) Y chromosome
C) Both
D) Autosomes -
Turner syndrome occurs due to:
A) Monosomy
B) Trisomy
C) Duplication
D) Polyploidy -
The number of sex chromosomes in a normal human cell is:
A) 2
B) 4
C) 1
D) 0
Answer Key
- B | 2. B | 3. A | 4. B | 5. B | 6. B | 7. B | 8. B | 9. D | 10. A
- B | 12. C | 13. B | 14. B | 15. C | 16. C | 17. A | 18. C | 19. C | 20. B
- C | 22. B | 23. B | 24. C | 25. C | 26. B | 27. B | 28. A | 29. C | 30. A
- B | 32. C | 33. C | 34. C | 35. A | 36. B | 37. A | 38. B | 39. A | 40. C
- D | 42. C | 43. B | 44. D | 45. B | 46. C | 47. B | 48. A | 49. A | 50. A
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