Complete Principles of Inheritance and Variation Question Bank & Solutions (70 Questions)
Q1 of 70
NEET NCERT Line-by-Line
Mendel is called the Father of Genetics for his work on:
(A)
Maize
(B)
Garden pea
(C)
Snapdragon
(D)
Fruit fly
Show Answer & NCERT Explanation
Correct Answer: (B) Garden pea
Mendel worked on Pisum sativum (garden pea).
Q2 of 70
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How many pairs of contrasting characters did Mendel study?
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Correct Answer: (C) 7
He studied seven pairs of contrasting traits.
Q3 of 70
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Which is NOT one of Mendel's seven traits?
(A)
Seed shape
(B)
Pod colour
(C)
Leaf size
(D)
Flower position
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Correct Answer: (C) Leaf size
Leaf size was not among the seven; flower position (axial/terminal) was.
Q4 of 70
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For flower colour, the dominant trait is:
(A)
White
(B)
Violet
(C)
Pink
(D)
Red
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Correct Answer: (B) Violet
Violet is dominant over white.
Q5 of 70
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The observable characteristic of an organism is its:
(A)
Genotype
(B)
Phenotype
(C)
Karyotype
(D)
Allele
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Correct Answer: (B) Phenotype
Phenotype = observable trait; genotype = genetic makeup.
Q6 of 70
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A heterozygous tall pea plant has the genotype:
(A)
TT
(B)
Tt
(C)
tt
(D)
TtTt
Show Answer & NCERT Explanation
Correct Answer: (B) Tt
Tt is heterozygous (one dominant, one recessive allele).
Q7 of 70
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The F2 phenotypic ratio in a monohybrid cross is:
(A)
1:1
(B)
3:1
(C)
9:3:3:1
(D)
1:2:1
Show Answer & NCERT Explanation
Correct Answer: (B) 3:1
Monohybrid F2 phenotype = 3:1.
Q8 of 70
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The F2 genotypic ratio in a monohybrid cross is:
(A)
3:1
(B)
1:2:1
(C)
9:3:3:1
(D)
2:1
Show Answer & NCERT Explanation
Correct Answer: (B) 1:2:1
Genotypes TT:Tt:tt = 1:2:1.
Q9 of 70
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The Punnett square was devised by:
(A)
Mendel
(B)
Morgan
(C)
R. C. Punnett
(D)
Sutton
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Correct Answer: (C) R. C. Punnett
Reginald C. Punnett devised it.
Q10 of 70
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The Law of Purity of Gametes is another name for the Law of:
(A)
Dominance
(B)
Segregation
(C)
Independent Assortment
(D)
Linkage
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Correct Answer: (B) Segregation
Alleles separate pure into gametes — Law of Segregation.
Q11 of 70
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A test cross is a cross between F1 and a:
(A)
Homozygous dominant
(B)
Homozygous recessive
(C)
Heterozygote
(D)
Different species
Show Answer & NCERT Explanation
Correct Answer: (B) Homozygous recessive
Crossing with a homozygous recessive reveals the genotype.
Q12 of 70
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In snapdragon, Red × White gives Pink in F1. This is:
(A)
Co-dominance
(B)
Incomplete dominance
(C)
Complete dominance
(D)
Epistasis
Show Answer & NCERT Explanation
Correct Answer: (B) Incomplete dominance
Intermediate blend = incomplete dominance.
Q13 of 70
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F2 ratio in incomplete dominance is:
(A)
3:1
(B)
1:2:1
(C)
9:3:3:1
(D)
1:1
Show Answer & NCERT Explanation
Correct Answer: (B) 1:2:1
Phenotype ratio equals genotype ratio 1:2:1.
Q14 of 70
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Human AB blood group is an example of:
(A)
Incomplete dominance
(B)
Co-dominance
(C)
Epistasis
(D)
Pleiotropy
Show Answer & NCERT Explanation
Correct Answer: (B) Co-dominance
Both Iᴬ and Iᴮ are expressed — co-dominance.
Q15 of 70
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The number of alleles controlling ABO blood groups is:
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Correct Answer: (C) 3
Iᴬ, Iᴮ and i — an example of multiple allelism.
Q16 of 70
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The genotype of blood group O is:
(A)
IᴬIᴬ
(B)
IᴬIᴮ
(C)
ii
(D)
Iᴮi
Show Answer & NCERT Explanation
Correct Answer: (C) ii
O = homozygous ii (no antigen).
Q17 of 70
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The genotype of blood group AB is:
(A)
IᴬIᴬ
(B)
IᴬIᴮ
(C)
ii
(D)
Iᴮi
Show Answer & NCERT Explanation
Correct Answer: (B) IᴬIᴮ
AB = IᴬIᴮ (co-dominance).
Q18 of 70
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F2 phenotypic ratio of a dihybrid cross is:
(A)
3:1
(B)
1:2:1
(C)
9:3:3:1
(D)
1:1:1:1
Show Answer & NCERT Explanation
Correct Answer: (C) 9:3:3:1
Dihybrid F2 = 9:3:3:1.
Q19 of 70
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The Law of Independent Assortment is derived from a:
(A)
Monohybrid cross
(B)
Dihybrid cross
(C)
Test cross
(D)
Back cross
Show Answer & NCERT Explanation
Correct Answer: (B) Dihybrid cross
It needs two trait pairs — the dihybrid cross.
Q20 of 70
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The Chromosomal Theory of Inheritance was proposed by:
(A)
Morgan & Sturtevant
(B)
Sutton & Boveri
(C)
Watson & Crick
(D)
Bateson & Punnett
Show Answer & NCERT Explanation
Correct Answer: (B) Sutton & Boveri
Sutton and Boveri (1902).
Q21 of 70
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Morgan carried out his linkage experiments on:
(A)
Pea
(B)
Maize
(C)
Drosophila
(D)
Neurospora
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Correct Answer: (C) Drosophila
Drosophila melanogaster (fruit fly).
Q22 of 70
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Genes located close together on a chromosome show:
(A)
High recombination
(B)
Low recombination
(C)
No linkage
(D)
Independent assortment
Show Answer & NCERT Explanation
Correct Answer: (B) Low recombination
Closely placed genes are tightly linked → low recombination.
Q23 of 70
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Genetic maps based on recombination frequency were made by:
(A)
Morgan
(B)
Sturtevant
(C)
Bridges
(D)
Muller
Show Answer & NCERT Explanation
Correct Answer: (B) Sturtevant
Alfred Sturtevant constructed genetic maps.
Q24 of 70
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Human skin colour is an example of:
(A)
Pleiotropy
(B)
Co-dominance
(C)
Polygenic inheritance
(D)
Multiple allelism
Show Answer & NCERT Explanation
Correct Answer: (C) Polygenic inheritance
Many genes act additively — polygenic inheritance.
Q25 of 70
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One gene affecting several traits is called:
(A)
Polygeny
(B)
Pleiotropy
(C)
Epistasis
(D)
Linkage
Show Answer & NCERT Explanation
Correct Answer: (B) Pleiotropy
Pleiotropy — e.g. phenylketonuria.
Q26 of 70
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In grasshoppers the sex-determination system is:
(A)
XX–XY
(B)
ZW–ZZ
(C)
XX–XO
(D)
Haplodiploid
Show Answer & NCERT Explanation
Correct Answer: (C) XX–XO
Female XX, male XO (no Y).
Q27 of 70
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In birds, the female is:
(A)
ZZ
(B)
ZW
(C)
XX
(D)
XY
Show Answer & NCERT Explanation
Correct Answer: (B) ZW
Birds are ZW–ZZ; the female is heterogametic ZW.
Q28 of 70
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The sex of a human child is determined by the:
(A)
Mother's egg
(B)
Father's sperm
(C)
Temperature
(D)
Both parents equally
Show Answer & NCERT Explanation
Correct Answer: (B) Father's sperm
The father contributes X or Y — he is heterogametic.
Q29 of 70
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A male honeybee (drone) develops from:
(A)
A fertilised diploid egg
(B)
An unfertilised haploid egg
(C)
A worker larva
(D)
A fertilised haploid egg
Show Answer & NCERT Explanation
Correct Answer: (B) An unfertilised haploid egg
Drones arise from unfertilised (haploid) eggs by parthenogenesis.
Q30 of 70
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A drone honeybee has how many chromosomes?
(A)
8
(B)
16
(C)
32
(D)
64
Show Answer & NCERT Explanation
Correct Answer: (B) 16
Haploid drone = 16 (queen/worker = 32).
Q31 of 70
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Haemophilia is inherited as:
(A)
Autosomal dominant
(B)
Autosomal recessive
(C)
X-linked recessive
(D)
Y-linked
Show Answer & NCERT Explanation
Correct Answer: (C) X-linked recessive
X-linked recessive; a clotting factor is missing.
Q32 of 70
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In sickle-cell anaemia, glutamic acid is replaced by valine at position:
(A)
4th
(B)
6th
(C)
10th
(D)
1st
Show Answer & NCERT Explanation
Correct Answer: (B) 6th
6th position of the β-globin chain (GAG→GUG).
Q33 of 70
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The genotype of a sickle-cell carrier is:
(A)
HbᴬHbᴬ
(B)
HbᴬHbˢ
(C)
HbˢHbˢ
(D)
HbᴬHbᴮ
Show Answer & NCERT Explanation
Correct Answer: (B) HbᴬHbˢ
HbᴬHbˢ is the heterozygous carrier.
Q34 of 70
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Phenylketonuria results from lack of an enzyme converting:
(A)
Tyrosine → phenylalanine
(B)
Phenylalanine → tyrosine
(C)
Glucose → galactose
(D)
Lactose → glucose
Show Answer & NCERT Explanation
Correct Answer: (B) Phenylalanine → tyrosine
Phenylalanine is not converted to tyrosine and accumulates.
Q35 of 70
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Thalassemia is best described as a:
(A)
Qualitative globin defect
(B)
Quantitative globin defect
(C)
Chromosomal defect
(D)
Enzyme deficiency
Show Answer & NCERT Explanation
Correct Answer: (B) Quantitative globin defect
Reduced synthesis (quantity) of globin chains.
Q36 of 70
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Down's syndrome is caused by trisomy of chromosome:
(A)
18
(B)
21
(C)
23
(D)
13
Show Answer & NCERT Explanation
Correct Answer: (B) 21
An extra copy of chromosome 21.
Q37 of 70
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Klinefelter's syndrome has the karyotype:
(A)
45,X0
(B)
47,XXY
(C)
47,XYY
(D)
47,+21
Show Answer & NCERT Explanation
Correct Answer: (B) 47,XXY
47,XXY — sterile male with gynaecomastia.
Q38 of 70
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Turner's syndrome individuals are:
(A)
Sterile males
(B)
Fertile females
(C)
Sterile females
(D)
Normal males
Show Answer & NCERT Explanation
Correct Answer: (C) Sterile females
45,X0 — sterile females with rudimentary ovaries.
Q39 of 70
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Failure of chromosomes to separate during meiosis is:
(A)
Crossing over
(B)
Non-disjunction
(C)
Translocation
(D)
Inversion
Show Answer & NCERT Explanation
Correct Answer: (B) Non-disjunction
Non-disjunction leads to aneuploidy.
Q40 of 70
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Gain of a whole chromosome set is called:
(A)
Aneuploidy
(B)
Polyploidy
(C)
Monosomy
(D)
Trisomy
Show Answer & NCERT Explanation
Correct Answer: (B) Polyploidy
Polyploidy — common in plants.
Q41 of 70
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Colour blindness affects approximately what fraction of males?
(A)
0.4%
(B)
8%
(C)
20%
(D)
50%
Show Answer & NCERT Explanation
Correct Answer: (B) 8%
About 8% of males (0.4% of females).
Q42 of 70
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Mendel's 'factors' correspond to modern:
(A)
Chromosomes
(B)
Genes
(C)
Enzymes
(D)
Proteins
Show Answer & NCERT Explanation
Correct Answer: (B) Genes
Factors = genes; their variants = alleles.
Q43 of 70
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The recombinant phenotypes in a dihybrid F2 are:
(A)
Round-Yellow & Wrinkled-Green
(B)
Round-Green & Wrinkled-Yellow
(C)
Only Round-Yellow
(D)
Only Wrinkled-Green
Show Answer & NCERT Explanation
Correct Answer: (B) Round-Green & Wrinkled-Yellow
New non-parental combinations: Round-Green and Wrinkled-Yellow.
Q44 of 70
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A cross of F1 with a parent is a:
(A)
Test cross
(B)
Back cross
(C)
Reciprocal cross
(D)
Dihybrid cross
Show Answer & NCERT Explanation
Correct Answer: (B) Back cross
Back cross = F1 × either parent.
Q45 of 70
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Mendel's work was rediscovered in 1900 by:
(A)
Sutton, Boveri, Morgan
(B)
de Vries, Correns, von Tschermak
(C)
Watson, Crick, Wilkins
(D)
Darwin, Wallace, Lamarck
Show Answer & NCERT Explanation
Correct Answer: (B) de Vries, Correns, von Tschermak
de Vries, Correns and von Tschermak independently rediscovered it.
Q46 of 70
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The heterogametic sex in humans is:
(A)
Female (XX)
(B)
Male (XY)
(C)
Both
(D)
Neither
Show Answer & NCERT Explanation
Correct Answer: (B) Male (XY)
Male XY produces two kinds of gametes.
Q47 of 70
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Which condition is a qualitative disorder of haemoglobin?
(A)
Thalassemia
(B)
Sickle-cell anaemia
(C)
Down's syndrome
(D)
Turner's syndrome
Show Answer & NCERT Explanation
Correct Answer: (B) Sickle-cell anaemia
Sickle-cell — abnormal (wrong-quality) globin.
Q48 of 70
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Which is an example of pleiotropy?
(A)
Skin colour
(B)
Height
(C)
Phenylketonuria
(D)
ABO blood group
Show Answer & NCERT Explanation
Correct Answer: (C) Phenylketonuria
PKU — one gene, many effects.
Q49 of 70
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In a test cross giving 1:1 offspring, the tested parent was:
(A)
Homozygous dominant
(B)
Heterozygous
(C)
Homozygous recessive
(D)
Sterile
Show Answer & NCERT Explanation
Correct Answer: (B) Heterozygous
A 1:1 ratio indicates the tested parent was heterozygous.
Q50 of 70
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The characteristic single palm crease is seen in:
(A)
Turner's
(B)
Klinefelter's
(C)
Down's syndrome
(D)
Haemophilia
Show Answer & NCERT Explanation
Correct Answer: (C) Down's syndrome
Down's syndrome features a broad palm with a characteristic crease.
Q51 of 70
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The probability of obtaining a homozygous recessive (tt) plant from a Tt × Tt cross is:
(A)
1/2
(B)
1/4
(C)
3/4
(D)
1/3
Show Answer & NCERT Explanation
Correct Answer: (B) 1/4
Genotypes are 1 TT : 2 Tt : 1 tt, so tt = 1/4.
Q52 of 70
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A plant of genotype AaBbCc produces how many types of gametes?
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Correct Answer: (C) 8
2ⁿ = 2³ = 8 gamete types.
Q53 of 70
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The F2 phenotypic ratio of a trihybrid cross is:
(A)
9:3:3:1
(B)
27:9:9:9:3:3:3:1
(C)
1:1:1:1
(D)
3:1
Show Answer & NCERT Explanation
Correct Answer: (B) 27:9:9:9:3:3:3:1
Three independent gene pairs give the 27:9:9:9:3:3:3:1 ratio.
Q54 of 70
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The phenotypic ratio of a dihybrid test cross (RrYy × rryy) is:
(A)
9:3:3:1
(B)
3:1
(C)
1:1:1:1
(D)
1:2:1
Show Answer & NCERT Explanation
Correct Answer: (C) 1:1:1:1
All four gamete types meet ry, giving equal 1:1:1:1 classes.
Q55 of 70
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If a carrier woman for colour blindness marries a man with normal vision, the percentage of colour-blind sons expected is:
(A)
0%
(B)
25%
(C)
50%
(D)
100%
Show Answer & NCERT Explanation
Correct Answer: (C) 50%
Half the sons inherit her X^c and are colour-blind.
Q56 of 70
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The number of Barr bodies in a Klinefelter (XXY) individual is:
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Correct Answer: (B) 1
Barr bodies = (X count − 1) = 2 − 1 = 1.
Q57 of 70
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The number of Barr bodies in a Turner (XO) individual is:
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Correct Answer: (A) 0
One X, so 1 − 1 = 0 Barr bodies.
Q58 of 70
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The number of autosomes present in a normal human sperm is:
(A)
44
(B)
23
(C)
22
(D)
46
Show Answer & NCERT Explanation
Correct Answer: (C) 22
A gamete is haploid: 22 autosomes + 1 sex chromosome.
Q59 of 70
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Mendel presented his classic paper on inheritance in the year:
(A)
1859
(B)
1866
(C)
1900
(D)
1905
Show Answer & NCERT Explanation
Correct Answer: (B) 1866
He published in 1866; it was rediscovered in 1900.
Q60 of 70
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A person with the Bombay phenotype has the genotype:
(A)
I^A I^A HH
(B)
hh (I^A/I^B not expressed)
(C)
ii HH
(D)
I^B i hh only
Show Answer & NCERT Explanation
Correct Answer: (B) hh (I^A/I^B not expressed)
hh blocks the H antigen, so A/B cannot be displayed and the person tests as O.
Q61 of 70
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A cross between a blood group AB parent and a group O parent can give children of group(s):
(A)
Only O
(B)
A and B
(C)
AB and O
(D)
A, B, AB and O
Show Answer & NCERT Explanation
Correct Answer: (B) A and B
I^A I^B × ii → I^A i (A) and I^B i (B).
Q62 of 70
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Erythroblastosis foetalis is most likely when:
(A)
Rh⁺ mother carries an Rh⁻ foetus
(B)
Rh⁻ mother carries a second Rh⁺ foetus
(C)
Both parents are Rh⁻
(D)
Mother is Rh⁺ in first pregnancy
Show Answer & NCERT Explanation
Correct Answer: (B) Rh⁻ mother carries a second Rh⁺ foetus
A sensitised Rh⁻ mother attacks a later Rh⁺ foetus's RBCs.
Q63 of 70
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The mutation causing sickle-cell haemoglobin changes the codon:
(A)
GAG → GUG
(B)
GUG → GAG
(C)
AUG → GUG
(D)
GAA → GAG
Show Answer & NCERT Explanation
Correct Answer: (A) GAG → GUG
GAG (glutamic acid) → GUG (valine) at position 6 of β-globin.
Q64 of 70
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Holandric genes are located on the:
(A)
X chromosome
(B)
Y chromosome
(C)
Autosomes
(D)
Mitochondrial DNA
Show Answer & NCERT Explanation
Correct Answer: (B) Y chromosome
They lie on the Y and pass father → all sons.
Q65 of 70
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A colour-blind daughter can be born only if:
(A)
The father is colour-blind and the mother is at least a carrier
(B)
The mother alone is a carrier
(C)
The father alone is colour-blind
(D)
Neither parent carries it
Show Answer & NCERT Explanation
Correct Answer: (A) The father is colour-blind and the mother is at least a carrier
She needs an X^c from each parent, so the father must be affected and the mother a carrier or affected.
Q66 of 70
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The phenotypic ratio of an Aa × aa cross is:
(A)
3:1
(B)
1:2:1
(C)
1:1
(D)
9:3:3:1
Show Answer & NCERT Explanation
Correct Answer: (C) 1:1
Half the offspring are Aa and half aa — a 1:1 ratio.
Q67 of 70
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Two parents of blood group AB can NOT have a child of group:
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Correct Answer: (D) O
Neither parent carries the i allele needed for group O.
Q68 of 70
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Klinefelter's syndrome individuals are:
(A)
Fertile females
(B)
Sterile males with some feminine features
(C)
Fertile males
(D)
Short sterile females
Show Answer & NCERT Explanation
Correct Answer: (B) Sterile males with some feminine features
XXY males are typically tall, sterile, with gynaecomastia.
Q69 of 70
NEET NCERT Line-by-Line
Failure of homologous chromosomes to separate in meiosis is called:
(A)
Crossing over
(B)
Non-disjunction
(C)
Synapsis
(D)
Translocation
Show Answer & NCERT Explanation
Correct Answer: (B) Non-disjunction
Non-disjunction yields gametes with extra/missing chromosomes.
Q70 of 70
NEET NCERT Line-by-Line
In snapdragon, a cross of pink (Rr) × pink (Rr) gives an F2 phenotypic ratio of:
(A)
3 red : 1 white
(B)
1 red : 2 pink : 1 white
(C)
9:3:3:1
(D)
1 red : 1 white
Show Answer & NCERT Explanation
Correct Answer: (B) 1 red : 2 pink : 1 white
Incomplete dominance keeps genotype and phenotype ratios identical: 1:2:1.