CBSE Class 12 Biology Principles of Inheritance and Variation MCQs

Question: All genes located on the same chromosome

a) Form one linkage group

b) Will not from any linkage groups

c) Form interactive groups that affect the phenotype

Answer :  A

Question: Conditions of a karyotype 2n ± 1 and 2n ± 2 are called

a) Aneuploidy

b) Polyploidy

c) Allopolyploidy

d) Monosomy

Answer :  A

Question: Distance between the genes and percentage of recombination shows

a) an inverse relationship

b) a parallel relationship

c) no relationship

d) a direct relationship

Answer :  A

Question: If a genetic disease is transferred from a phenotypically normal but carrier female to only some of the male progeny, the disease is

a) Sex-linked recessive

b) Autosomal dominant

c) Sex-linked dominant

d) Autosomal recessive

Answer :  A

Question: In sickle cell anaemia glutamic acid is replaced by valine. Which one of the following triplets codes for valine?

a) G U G

b) G A A

c) A A G

d) G G G

Answer :  A

Question: Thalassemia and sickle cell anemia are caused due to a problem in globin molecule synthesis. Select the correct statement

a) Thalassemia is due to less synthesis of globin molecules

b) Both are due to a quantitative defect in globin chain synthesis

c) Both are due to a qualitative defect in globin chain synthesis

d) All of these

Answer :  A

Question: Among the following characters, which one was not considered by Mendel in his experiments on pea?

a) Among the following characters

b) Seed – Green or Yellow

c) Pod – Inflated or Constricted

d) Pod – Inflated or Constricted

Answer :  A

Question: Which one from those given below is the period

a) 1856 - 1863

b) 1840 - 1850

c) 1857 - 1869

d) 1870 - 1877

Answer :  A

Question: A disease caused by an autosomal primary non-disjunction is

a) Down's syndrome

b) Klinefelter's syndrome

c) Turner's syndrome

d) Turner's syndrome

Answer :  A

Question: If a colour-blind man marries a woman who is homozygous for normal colour vision, the probability of their son being colour-blind is

a) 0

b) 0.5

c) 1

d) 2

Answer :  A

Question: Person having genotype IA IB would show the blood group as AB. This is because of

a) Co-dominance

b) Pleiotropy

c) Segregation

d) Incomplete dominance

Answer :  A

Question: Z Z / ZW type of sex determination is seen in:

a) Peacock

b) Cockroach

c) Platypus

d) Snails

Answer :  A

Question: A Across between two tall plants resulted in offspring having few dwarf plants. What would be the genotypes of both the parents?

a) Tt and Tt

b) TT and Tt

c) TT and TT

d) Tt and tt

Answer :  A

Question: In a dihybrid cross, if you get 9:3:3:1 ratio it denotes that

a) The allels of two genes are segregating independently.

b) It is a case of multiple allelism

c) It is a multigenic inheritance

d) The allels of two genes are interacting with each other

Answer :  A

Question: Which of the following will not result in variations among siblings?

a) Linkage

b) Mutation

c) Independent assortment of genes

d) Crossing over

Answer :  A

Question: In a testcross involving F1 dihybrid flies, more parental-type offspring were produced than the recombinant-type offspring. This indicates

a) The two genes are linked and present on the same chromosome.

b) Both of the characters are controlled by more than one gene

c) Both of the characters are controlled by more than one gene

d) None of these

Answer :  A.

Question: How many pairs of contrasting characters in pea plants were studied by Mendel in his experiments?

a) 7

b) 5

c) 6

d) 4

Answer :  A

Question: If a hybrid expresses a character, is it called

a) Dominant

b) Co-dominant

c) Recessive

d) Epistaxis

Answer :  A

Question: A plant having the genotype AABbCC will produce ______ kinds of gametes

a) 4

b) 3

c) 2

d) 1

Answer :  A

Question: A man with blood group 'A' marries a woman with blood group 'B'. What are all the possible blood groups of their offsprings?

a) A, B, AB and O

b) A, B and AB only

c) A and B only

d) None of these

Answer :  A

Question: Two linked genes a and b show 20% recombination.

The individuals of a dihybrid cross between ++ /++ × ab/ab shall show gametes

a) + +80 : ab 20

b) + + 50 : ab 50

c) + + 40 : ab 40 : + a 10 : + b : 10

d) + + 30 : ab 30 : + a 20 : + b : 20

Answer :   C

Question: A normal green male maize is crossed with albino female. The progeny is albino because

a) trait for albinism is dominant

b) the albinos have biochemical to destroy plastids derived from green male

c) plastids are inherited from female parent

d) green plastids of male must have mutated

Answer : C

Question: Multiple alleles control inheritance of

a) phenylketonuria

b) colourblindness

c) sickle cell anaemia

d) blood groups

Answer : D

Question: Blue eye colour is recessive to brown eye colour. A brown eyed man whose mother was blue eyed marries a blue eyed women. The children shall be 

a) both blue eyed and brown eyed 1 : 1

b) all brown eyed

c) all blue eyed

d) blue eyed and brown eyed 3 :1

Answer : A

Question: A dihybrid condition is 
a) ttRr
b) Tt rr
c) tt rr
d) Tt Rr

Answer : D

Question: Mendel’s last law is 
a) segregation
b) dominance
c) independent assortment
d) polygenic inheritance

Answer : C

Question: First geneticist/father of genetics was 
a) de Vries
b) Mendel
c) Darwin
d) Morgan

Answer : B

Question: The contrasting pairs of factors in Mendelian crosses are called 
a) multiple alleles
b) allelomorphs
c) alloloci
d) paramorphs

Answer : B

Question: The allele which is unable to express its effect in the presence of another is called 
a) codominant
b) supplementary
c) complementary
d) recessive

Answer : D

Question: RR (red) Antirrhinum is crossed with WW (white) one. Offspring RW are pink. This is an example of 

a) dominant-recessive

b) incomplete dominance

c) hybrid

d) supplementary genes

Answer : B

Question: A gene pair hides the effect of another. The phenomenon is 
a) epistasis
b) dominance
c) mutation
d) None of these

Answer : A

Question: An allele is dominant if it is expressed in 

a) both homozygous and heterozygous states

b) second generation

c) heterozygous combination

d) homozygous combination

Answer : A

Question: In a cross between AABB × aabb, the ratio of F₂ genotypes between AABB, AaBB, Aabb and aabb would be 
a) 9 : 3 : 3 : 1
b) 2 : 1 : 1 : 2
c) 1 : 2 : 2 : 1
d) 7 : 5 : 3 : 1

Answer : C

Question: Segregation of Mendelian factors (no linkage, no crossing over) occurs during 
a) anaphase-I
b) anaphase-II
c) diplotene
d) metaphase-I

Answer : A

Question: An organism with two identical alleles is 
a) dominant
b) hybrid
c) heterozygous
d) homozygous

Answer : D

Question: When a certain character is inherited only through female parent, it probably represents

a) multiple plastid inheritance 

b) cytoplasmic inheritance

c) incomplete dominance

d) Mendelian nuclear inheritance

Answer : B

Question: A polygenic inheritance in human beings is

a) skin colour 

b) phenylketonuria

c) colourblindness

d) sickle cell anaemia

Answer : A

Question: Mendel studied interitance of seven pairs of traits in pea which can have 21 possible combinations. If you are told that in one of these combinations, independent assortment is not observed in later studies, your reaction will be 

a) independent assortment principle may be wrong

b) Mendel might not have studied all the combinations

c) it is impossible

d) later studies may be wrong

Answer : B

Question: Two dominant non-allelic genes are 50 map units apart. The linkage is 
a) cis type
b) trans type
c) complete
d) absent/incomplete

Answer : D

Question: Which of the following is suitable for experiment on linkage? 
a) aaBB × aaBB
b) AABB × aabb
c) AaBb × AaBb
d) AAbb × AaBB

Answer : B

Question: Haploid plants are preferred over diploids for mutation study because in haploids 

a) recessive mutation express immediately

b) induction of mutations is easier

c) culturing is easier

d) dominant mutation express immediately

Answer : A

Question: The process of mating between closely related individuals is 
a) self breeding
b) inbreeding
c) hybridization
d) heterosis

Answer : B

Question: A fruit fly exhibiting both male and female traits is 
a) heterozygous
b) gynandromorph
c) hemizygous
d) gynander

Answer : B

Question: A woman with albinic father marries an albinic man. The proportion of her progeny is 

a) 2 normal : 1 albinic

b) all normal

c) all albinic 

d) 1 normal : 1 albinic

Answer : D

Question: A cross between pure tall pea plant with green pods and dwarf pea plant with yellow pods will produce dwarf F2 plants out of 16
a) 9
b) 3
c) 4
d) 1

Answer : C

Question: In a dihybrid cross AABB x aabb, F2 progeny of AABB, AABb, AaBB and AaBb occurs in the ratio of
 a) 1 : 1 : 1 : 1
b) 9 : 3 : 3 : 1
c) 1 : 2 : 2 : 1
d) 1 : 2 : 2 : 4

Answer : D

Question: When two genetic loci produce identical phenotypes in cis and trans position, they are considered to be

a) pseudoalleles

b) different genes

c) multiple alleles

d) parts of same gene

Answer : A

Question: Alleles that produce independent effects in their heterozygous condition are called

a) codominant alleles

b) epistatic alleles

c) complementary alleles

d) supplementary alleles

Answer : A

Question: A fruit fly heterozygous for sex-linked genes, is mated with normal female fruit fly. Male specific chromosome will enter egg cell in the proportion
a) 1 : 1
b) 2 : 1
c) 3 : 1
d) 7 : 1

Answer : A

Question: When a single gene influences more than one traits it is called

a) pleiotropy

b) epistasis

c) pseudodominance

d) None of these

Answer : A

Question: If Mendel had studied the seven traits using a plant with 12 chromosomes instead of 14, in what way would his interpretation have been different? 

a) He would have mapped the chromosome

b) He would have discovered blending or incomplete dominance

c) He would not have discovered the law of independent assortment

d) He would have discovered sex-linkage

Answer : C

Question: Mendel’s Law of independent assortment holds good for genes situated on the:

a) non-homologous chromosomes

b) homologous chromosomes

c) extra nuclear genetic element

d) same chromosome

Answer: A

Question: Occasionally, a single gene may express more than one effect. The phenomenon is called

a) pleiotropy

b) mosaicism

c) polygeny

d) multiple allelism

Answer: A

Question: In a certain taxon of insects some have 17 chromosomes and the others have 18 chromosomes. The 17 and 18 chromosome-bearing organisms are:

a) males and females, respectively

b) females and males, respectively

c) all males

d) all females

Answer: A

Question: The inheritance pattern of a gene over generations among humans is studied by the pedigree analysis. Character studied in the pedigree analysis is equivalent to:

a) Mendelian trait

b) polygenic trait

c) maternal trait

d) quantitative trait

Answer: A

Question: Where are the genes for cytoplasmic male sterility in plants located?

a) Mitochondrial genome

b) Cytosome

c) Cytosome

d) None of these

Answer: A

Question: _________ is a type of trait whose phenotype is influenced by more than one gene

a) Polygenic trait

b) Monogenic trait

c) Both

d) None of these

Answer: A

Question: It is said that Mendel proposed that the factor controlling any character is discrete and independent. This proposition was based on the

a) observations that the offspring of a cross made between the plants having two contrasting characters shows only one character without any blending

b) self pollination of F₁ offsprings

c) cross pollination of parental generations

d) All of these

Answer: A

Question: Two genes ‘A’ and ‘B’ are linked. In a dihybrid cross involving these two genes, the F₁ heterozygote is crossed with homozygous recessive parental type (aa bb). What would be the ratio of offspring in the next generation?

a) 1 : 1 : 1: 1

b) 9 : 3 : 3 : 1

c) 3 : 1

d) 1 : 1

Answer: A

Question: Mother and father of a person with ‘O’ blood group have ‘A’ and ‘B’ blood group respectively. What would be the genotype of both mother and father?

a) Both mother and father are heterozygous for ‘A’ and ‘B’ blood group, respectively

b) Both mother and father are homozygous for ‘A’ and ‘B’ blood group, respectively

c) Mother is heterozygous for ‘A’ blood group and father is homozygous for ‘B

d) Mother is homozygous for ‘A’ blood group and father is heterozygous for ‘B’

Answer: A

Question: A pleiotropic gene

a) controls multiple traits in an individual

b) controls multiple traits in an individual

c) is a gene evolved during Pliocene

d) control of trait only in combination with another gene

Answer: A