NEET MCQs Practice on Principles of Inheritance and Variation Class-XII Biology, Free unlimited practice on Principles of Inheritance and Variation Class-XII Biology Mcqs

Match List-I (Genetic Disorder) with List-II (Defining Feature):

List-I	List-II
A. Haemophilia	I. X-linked recessive, single protein in clotting cascade affected
B. Colour blindness	II. Defect in red or green cone of eye, X-linked recessive
C. Sickle-cell anaemia	III. Autosomal recessive, polymerisation of mutant haemoglobin
D. Phenylketonuria	IV. Autosomal recessive, lack of enzyme converting phenylalanine to tyrosine

Choose the correct answer from the options given below:

[Principles-of-Inheritance-and-Variation] [class-xii ]

A-I, B-II, C-III, D-IV
A-II, B-I, C-IV, D-III
A-III, B-IV, C-I, D-II
A-IV, B-III, C-II, D-I

Correct Option: A [ A-I, B-II, C-III, D-IV ]

Remark: Haemophilia is an X-linked recessive disorder where a clotting protein is affected. Colour blindness is an X-linked recessive disorder due to cone cell defects. Sickle-cell anaemia is autosomal recessive leading to haemoglobin polymerisation. Phenylketonuria is autosomal recessive caused by the lack of the enzyme phenylalanine hydroxylase.

Match List-I (Monohybrid Genotype) with List-II (F2 Proportion):

List-I (Genotype)	List-II (Proportion in F2)
A. TT (Homozygous Dominant)	I. 1/4
B. Tt (Heterozygous)	II. 1/2
C. tt (Homozygous Recessive)	III. 1/4
D. Tt (Phenotype expressed)	IV. Tall

Choose the correct answer from the options given below:

[Principles-of-Inheritance-and-Variation] [class-xii ]

A-I, B-II, C-III, D-IV
A-II, B-I, C-IV, D-III
A-III, B-IV, C-I, D-II
A-IV, B-III, C-II, D-I

Correct Option: A [ A-I, B-II, C-III, D-IV ]

Remark: In the F2 generation of a monohybrid cross, the genotypic ratio TT:Tt:tt is 1/4 : 1/2 : 1/4. The heterozygous Tt plant expresses the tall phenotype.

Match List-I (Haplodiploid Male Feature) with List-II (Consequence):

List-I (Drone Feature)	List-II (Result)
A. Develops from unfertilised egg	I. Is haploid (16 chromosomes)
B. Produces sperm by Mitosis	II. Sperm are genetically identical to the male
C. Does not have a father	III. Cannot have sons
D. Has a grandfather	IV. Can have grandsons

Choose the correct answer from the options given below:

[Principles-of-Inheritance-and-Variation] [class-xii ]

A-I, B-II, C-III, D-IV
A-II, B-I, C-IV, D-III
A-III, B-IV, C-I, D-II
A-IV, B-III, C-II, D-I

Correct Option: A [ A-I, B-II, C-III, D-IV ]

Remark: Males develop from unfertilized eggs (parthenogenesis) and are haploid. Sperm production by mitosis maintains the male's genetic makeup. Males lack a father, meaning they cannot have sons, but they do have a grandfather and can have grandsons.

Match List-I (Inheritance Type) with List-II (Phenotypic Trait/Condition):

List-I	List-II
A. Single gene multiple effect	I. Pleiotropy (e.g., Phenylketonuria)
B. Multiple genes plus environment	II. Polygenic inheritance (e.g., Human height)
C. Intermediate phenotype in F1	III. Incomplete Dominance (e.g., Pink Snapdragon)
D. F1 resembles both parents	IV. Co-dominance (e.g., AB blood type)

Choose the correct answer from the options given below:

[Principles-of-Inheritance-and-Variation] [class-xii ]

A-I, B-II, C-III, D-IV
A-II, B-I, C-IV, D-III
A-III, B-IV, C-I, D-II
A-IV, B-III, C-II, D-I

Correct Option: A [ A-I, B-II, C-III, D-IV ]

Remark: Single gene multiple effect is pleiotropy. Multiple genes plus environment characterize polygenic inheritance. Intermediate phenotype in F1 is incomplete dominance. F1 resembling both parents is co-dominance.

Match List-I (Chromosomal Disorder Symptom) with List-II (Affected Organ/System):

List-I (Symptom/Feature)	List-II (Syndrome)
A. Mental retardation, partially open mouth	I. Down’s Syndrome (Trisomy 21)
B. Gynaecomastia	II. Klinefelter’s Syndrome (XXY)
C. Rudimentary ovaries	III. Turner’s Syndrome (X0)
D. Polyploidy (in plants)	IV. Increase in a whole set of chromosomes

Choose the correct answer from the options given below:

[Principles-of-Inheritance-and-Variation] [class-xii ]

A-I, B-II, C-III, D-IV
A-II, B-I, C-IV, D-III
A-III, B-IV, C-I, D-II
A-IV, B-III, C-II, D-I

Correct Option: A [ A-I, B-II, C-III, D-IV ]

Remark: Mental retardation and partially open mouth are signs of Down’s Syndrome. Gynaecomastia is breast development seen in Klinefelter’s Syndrome. Rudimentary ovaries characterize Turner’s Syndrome. Polyploidy is the increase in a whole set of chromosomes.

Match List-I (Gamete Type) with List-II (Sex/Organism):

List-I (Gamete types produced)	List-II (Sex/Mechanism)
A. X or Y chromosome carrying sperm	I. Male heterogamety (Humans/Drosophila)
B. X or no X carrying sperm	II. Male heterogamety (Grasshopper)
C. Z or W chromosome carrying ovum	III. Female heterogamety (Birds)
D. Only X carrying ovum	IV. Female homogamety (Humans/Drosophila)

Choose the correct answer from the options given below:

[Principles-of-Inheritance-and-Variation] [class-xii ]

A-I, B-II, C-III, D-IV
A-II, B-I, C-IV, D-III
A-III, B-IV, C-I, D-II
A-IV, B-III, C-II, D-I

Correct Option: A [ A-I, B-II, C-III, D-IV ]

Remark: X or Y sperm indicates XY mechanism (Male heterogamety). X or O sperm indicates XO mechanism (Male heterogamety). Z or W ova indicates ZW mechanism (Female heterogamety). Only X ova indicates XX mechanism (Female homogamety).

Match List-I (Allele Relationship) with List-II (Description of Allele):

List-I	List-II
A. Dominant Allele	I. Unmodified (functioning) allele that produces normal enzyme
B. Recessive Allele (typical)	II. Modified allele producing non-functional or no enzyme
C. Allele producing less efficient enzyme	III. May lead to an effected (recessive) phenotype
D. Allele producing equivalent enzyme	IV. Results in the same phenotype as the unmodified allele

Choose the correct answer from the options given below:

[Principles-of-Inheritance-and-Variation] [class-xii ]

A-I, B-II, C-III, D-IV
A-II, B-I, C-IV, D-III
A-III, B-IV, C-I, D-II
A-IV, B-III, C-II, D-I

Correct Option: A [ A-I, B-II, C-III, D-IV ]

Remark: The dominant allele is usually the unmodified, functioning allele. The recessive allele is often the modified allele producing non-functional or no enzyme. A modified allele producing a less efficient enzyme may still affect the phenotype (III). An equivalent enzyme results in the same phenotype (IV).

Match List-I (Human Genetic Disorder) with List-II (Inheritance Pattern):

List-I (Disorder)	List-II (Inheritance)
A. Haemophilia	I. X-linked recessive
B. Sickle-cell anaemia	II. Autosome linked recessive
C. Myotonic dystrophy	III. Autosomal dominant
D. Colour Blindness	IV. X-linked recessive

Choose the correct answer from the options given below:

[Principles-of-Inheritance-and-Variation] [class-xii ]

A-I, B-II, C-III, D-IV
A-II, B-I, C-IV, D-III
A-III, B-IV, C-I, D-II
A-IV, B-III, C-II, D-I

Correct Option: A [ A-I, B-II, C-III, D-IV ]

Remark: Haemophilia is an X-linked recessive disease. Sickle-cell anaemia is an autosome-linked recessive trait. Myotonic dystrophy is an example of an autosomal dominant trait. Colour blindness is an X-linked recessive disorder.

Assertion (A):
In a monohybrid cross between tall (TT) and dwarf (tt) pea plants, all the F₁ progeny are tall.
Reason (R):
The Law of Dominance states that in a dissimilar pair of factors, one factor (T) dominates the other (t), and is expressed in the F₁ generation.

[Principles-of-Inheritance-and-Variation] [class-xii ]

(A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion
(B) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion
(C) Assertion is true but Reason is false
(D) Assertion is false but Reason is true

Correct Option: A [ A ]

Remark: Mendel observed that all F₁ progeny plants were tall. The Law of Dominance explains that in a dissimilar pair of factors, one dominates the other (dominant factor).

Assertion (A):
The recessive parental trait is expressed without any blending in the F₂ generation of a monohybrid cross.
Reason (R):
The Law of Segregation is based on the fact that alleles do not show any blending and they separate from each other during gamete formation.

[Principles-of-Inheritance-and-Variation] [class-xii ]

(A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion
(B) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion
(C) Assertion is true but Reason is false
(D) Assertion is false but Reason is true

Correct Option: A [ A ]

Remark: The recessive parental trait (dwarf) reappears in F₂ without blending. The Law of Segregation is based on the non-blending of alleles and their separation during gamete formation.

Principles of Inheritance and Variation: Class-XII

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