NEET 2027 - Class 12 Chapter 5 Principles of Inheritance and Variation question

Class 12 Biology -

Chapter 5
The Principles of Inheritance and Variation

50 NEET 2027 Level MCQs |
NCERT + PYQ Based

📘 SECTION A: NCERT BASED MCQs - Q1 to Q30

Q1 In which plant group are seeds naked?

a) Angiosperms

b) Gymnosperms

c) Pteridophytes

d) Bryophytes

Ans: b) Gymnosperms - Gymnos means naked. Seeds not enclosed in fruit.

Q1 Mendel selected pea plant because

a) Short life cycle

b) Many contrasting characters

c) Self pollination

d) All of these

Ans: d - All reasons.

Q2 The dominant phase in the life cycle of a bryophyte is:

a) Sporophyte

b) Gametophyte

c) Both equal

d) None

Ans: b) Gametophyte - Bryophytes gametophyte dominant.

Q3 Number of contrasting characters studied by Mendel

a) 5

b) 7

c) 8

d) 10

Ans: b) 7

Q4 Phenotypic ratio of monohybrid cross in F2

a) 1:1

b) 3:1

c) 9:3:3:1

d) 1:2:1

Ans: b) 3:1

Q5 Law of segregation is also called

a) Law of purity of gametes

b) Law of dominance

c) Law of independent assortment

d) None

Ans: a

Q6 Dihybrid ratio in F2

a) 3:1

b) 1:2:1

c) 9:3:3:1

d) 9:7

Ans: c) 9:3:3:1

Q7 Incomplete dominance seen in

a) Snapdragon

b) Pea

c) Drosophila

d) Human

Ans: a) Snapdragon - Red x White = Pink

Q8 Example of co-dominance

a) AB blood group

b) Snapdragon

c) Pea height

d) None

Ans: a) AB group

Q9 Multiple alleles present for

a) ABO blood group

b) Height

c) Skin colour

d) Eye colour

Ans: a) ABO has IA, IB, i

Q10 Pleiotropy is

a) One gene many phenotypes

b) Many genes one phenotype

c) One gene one phenotype

d) None

Ans: a) Eg. Phenylketonuria

Q11 Polygenic inheritance example

a) Human skin colour

b) ABO blood

c) Flower colour in pea

d) None

Ans: a

Q12 Who coined term linkage?

a) Mendel

b) Morgan

c) Bateson

d) Sutton

Ans: b) Morgan

Q13 Strength of linkage is

a) Directly proportional to distance

b) Inversely proportional to distance

c) No relation

d) Equal

Ans: b) Closer = stronger linkage

Q14 Chromosomal theory given by

a) Sutton and Boveri

b) Mendel

c) Morgan

d) Watson

Ans: a

Q15 Number of chromosomes in human

a) 44+2

b) 46

c) Both a and b

d) 44

Ans: c) 44 autosomes + 2 sex

Q16 Sex determination in humans is

a) XX-XY type

b) ZZ-ZW type

c) XX-XO type

d) Haplo-diploid

Ans: a) Male heterogametic

Q17 Sex determination in birds is

a) XX-XY

b) ZZ-ZW

c) XX-XO

d) None

Ans: b) Female heterogametic

Q18 Colour blindness is

a) Autosomal recessive

b) X-linked recessive

c) Y-linked

d) Autosomal dominant

Ans: b) More in males

Q19 Haemophilia is

a) X-linked recessive

b) Y-linked

c) Autosomal

d) Dominant

Ans: a) Bleeders disease

Q20 Down syndrome is due to

a) Trisomy 21

b) Trisomy 18

c) Trisomy 13

d) Monosomy

Ans: a) 47 chromosomes

Q21 Turner syndrome is

a) 44+XO

b) 44+XXY

c) 44+XXX

d) 44+YO

Ans: a) 45 chromosomes, female sterile

Q22 Klinefelter syndrome is

a) 44+XO

b) 44+XXY

c) 44+XXX

d) 44+YY

Ans: b) 47 chromosomes, male sterile

Q23 Sickle cell anaemia is

a) Autosomal recessive

b) Autosomal dominant

c) X-linked

d) Y-linked

Ans: a) 6th amino acid Glu to Val

Q24 Test cross is

a) F1 x recessive parent

b) F1 x dominant parent

c) F1 x F1

d) Parent x Parent

Ans: a) To know genotype

Q25 Distance between genes measured in

a) Centimorgan

b) Angstrom

c) Meter

d) Nanometer

Ans: a) 1% recombination = 1 cM

Q26 Number of gametes from AaBbCc

a) 4

b) 8

c) 16

d) 2

Ans: b) 2^3=8

Q27 Honey bee sex determination is

a) XX-XY

b) Haplo-diploid

c) ZZ-ZW

d) Environmental

Ans: b) Male haploid, female diploid

Q28 Crossing over occurs in

a) Leptotene

b) Pachytene

c) Diplotene

d) Zygotene

Ans: b) Pachytene of Prophase I

Q29 Barr body is found in

a) Females

b) Males

c) Both

d) None

Ans: a) One X inactivates in female

Q30 Number of Barr bodies in XXXX female

a) 1

b) 2

c) 3

d) 4

Ans: c) X-1 = 3

📗 SECTION B: PYQ Based MCQs - Q31 to Q40

Q31 A colour blind daughter is born when

a) Father colour blind, mother normal

b) Father normal, mother carrier

c) Father colour blind, mother carrier/colour blind

d) None

Ans: c) [NEET 2019]

Q32 The genotype of AB blood group

a) IA IA

b) IB IB

c) IA IB

d) ii

Ans: c) Co-dominance [NEET 2020]

Q33 Thalassemia is

a) Quantitative

b) Autosomal recessive

c) Due to less Hb production

d) Both b and c

Ans: d) [NEET 2021]

Q34 Phenylketonuria is

a) Autosomal recessive

b) Lack of phenylalanine hydroxylase

c) Example of pleiotropy

d) All of these

Ans: d) [NEET 2022]

Q35 Linkage map shows

a) Arrangement of genes

b) Distance between genes

c) Order of genes

d) All of these

Ans: d) [NEET 2023]

Q36 The disease showing criss-cross inheritance

a) X-linked recessive

b) Autosomal dominant

c) Y-linked

d) Autosomal recessive

Ans: a) Colour blindness [PYQ]

Q37 Father haemophilic, mother normal, daughters will be

a) All haemophilic

b) All carriers

c) 50% haemophilic

d) Normal

Ans: b) All carriers [NEET 2020]

Q38 Ratio 9:7 is due to

a) Complementary genes

b) Supplementary genes

c) Epistasis

d) Incomplete dominance

Ans: a) [NEET 2018]

Q39 The law rediscovered by Hugo de Vries

a) Law of dominance

b) Law of segregation

c) Both

d) None

Ans: c) All 3 laws in 1900 [PYQ]

Q40 Mother O group, father AB, children can be

a) A and B only

b) AB only

c) O only

d) All types

Ans: a) A and B only [NEET 2021]

📕 SECTION C: HIGH LEVEL / ASSERTION - Q41 to Q50

Q41 Assertion: Incomplete dominance shows 1:2:1 ratio. Reason: Phenotype intermediate.

a) Both true and reason correct explanation

b) Both true but reason not correct

c) Assertion true, reason false

d) Both false

Ans: a)

Q42 Human skin colour controlled by 3 genes, how many phenotypes in F2?

a) 3

b) 5

c) 7

d) 9

Ans: c) 7 - Number of dominant alleles 0 to 6

Q43 Match: Column I - Down (a), Turner (b), Klinefelter (c) with chromosomes

a) a-47(21), b-45XO, c-47XXY

b) a-45, b-47, c-46

c) a-46, b-45, c-47

d) None

Ans: a)

Q44 Genomic imprinting means

a) Gene expression depends on parent of origin

b) Gene always expressed

c) Gene never expressed

d) None

Ans: a)

Q45 Chance of son in human birth is

a) 25%

b) 50%

c) 75%

d) 100%

Ans: b) 50% - X and Y sperm equal

Q46 The gene causing sickle cell is on

a) Chromosome 11

b) Chromosome 12

c) Chromosome 6

d) X chromosome

Ans: a) Beta globin on 11, point mutation

Q47 Statement I: Linkage groups = haploid chromosome number. II: Humans have 23 linkage groups.

a) Both true

b) I true II false

c) I false II true

d) Both false

Ans: a) Both true

Q48 Number of Barr bodies in XXXY

a) 1

b) 2

c) 3

d) 2 in male also present

Ans: b) 2 - Formula X-1

Q49 Father with A blood group (IAi) and mother O (ii), child can have

a) Only A

b) A and O

c) B and O

d) AB

Ans: b) 50% A, 50% O

Q50 True about Morgan's Drosophila experiment

a) Yellow and white linked

b) Recombination 1.3% for close genes

c) Recombination 37% for distant genes

d) All of these

Ans: d) All true - proved linkage

🔑 ANSWER KEY - 50 Q - INHERITANCE AND VARIATION - NEET 2027

Q1-d

Q2-b

Q3-b

Q4-b

Q5-a

Q6-c

Q7-a

Q8-a

Q9-a

Q10-a

Q11-a

Q12-b

Q13-b

Q14-a

Q15-c

Q16-a

Q17-b

Q18-b

Q19-a

Q20-a

Q21-a

Q22-b

Q23-a

Q24-a

Q25-a

Q26-b

Q27-b

Q28-b

Q29-a

Q30-c

Q31-c

Q32-c

Q33-d

Q34-d

Q35-d

Q36-a

Q37-b

Q38-a

Q39-c

Q40-a

Q41-a

Q42-c

Q43-a

Q44-a

Q45-b

Q46-a

Q47-a

Q48-b

Q49-b

Q50-d

Click on any Question card to see explanation