CBSE Class 12 Biology Principles of Inheritance and Variation MCQs Set 06

Question: When a gene pair hides the effect of another, the phenomenon is called –
a) mutation
b) dominance
c) epistasis
d) none of these
Answer: c

Question: In the AB blood group the two genes are
a) codominant
b) corecessive
c) incompletely dominant
d) dominant-recessive
Answer: a

Question: A single recessive trait which can express its effect should occur on
a) any chromosome
b) any autosome
c) X chromosome of male
d) X chromosome of female
Answer: c

Question: The exposure of X-rays enhances the frequency of
a) linkage
b) crossing over
c) pairing of chromosomes
d) segregation
Answer: b

Question: Which of the following proved an exception to Mendel’s principles?
a) dominance
b) linkage
c) independent assortment
d) purity of gametes/segregation
Answer: b

Question: The different forms of a gene are called –
a) heterozygotes
b) alleles
c) supplementary genes
d) complementary genes
Answer: b

Question: Pleiotropic gene has –
a) single genotype
b) multiple genotype
c) multiple phenotype
d) single phenotype
Answer: c

Question: The substance which causes a definite change in genes is called
a) toxin
b) alkaloid
c) cytotoxin
d) mutagen
Answer: d

Question: Inheritance of skin colour in human beings is an example of –
a) polygenic inheritance
b) Mendelian inheritance
c) monogenic inheritance
d) complementary genes
Answer: a

Question: Haemophilia is more common in males because it is a –
a) Recessive trait carried by X chromosome
b) Dominant trait carried by X chromosome
c) Recessive character carried by Y chromosome
d) Dominant character carried by Y chromosome
Answer: a

Question: In codominance, the F1 generation resembles
a) Dominant parent
b) Recessive parent
c) Shows in–between character of both parents
d) None of these
Answer: d

Question: Who is considered as father of genetics?
a) Hugo de Vries
b) Morgan
c) Mendel
d) Darwin
Answer: c

Question: Organism showing dominant phenotype (heterozygous) is crossed with the recessive parent. It will produce –
a) 25% dominant and 75% recessive offspring
b) 50% dominant and 50% recessive offspring
c) 75% dominant and 25% recessive offspring
d) All dominant offspring
Answer: b

Question: The allelic pair of genes which are identical are known as
a) Homozygous
b) Heterozygous
c) Dominant
d) Recessive
Answer: a

Question: Multiple alleles control the character of –
a) Only skin colour
b) Only blood groups
c) Blood groups and skin colour
d) Sickle-cell
Answer: b

Question: If IA and Io are the alleles present in a person, which blood group is expressed?
a) B
b) A
c) O
d) AB
Answer: b

Question: The monohybrid cross of red and white flowers in snapdragon plant produced flowers of how many colours in F2 generation?
a) Three – red, white and orange
b) Two – red and white
c) Three – red, white and pink
d) All red
Answer: c

Question: Genes which code for a pair of contrasting traits are known as –
a) Factors
b) Alleles
c) Hybrids
d) None of these
Answer: b

Question: In monohybrid cross (TT × tt) the F1 and F2 generation each have how many small squares in Punnett square?
a) 4 in F1 and 16 in F2
b) 4 in F1 and 8 in F2
c) 4 each in F1 and F2
d) 2 in F1 and 4 in F2
Answer: a

Question: When in a monohybrid cross the F1 does not match to any of the parent and shows character in between the two, this is –
a) Law of dominance
b) Codominance
c) Law of segregation
d) Law of incomplete dominance
Answer: d

Question: How many alleles are there for blood group determining genes?
a) 2
b) 4
c) 3
d) None of these
Answer: c

Question: Gametes are produced by the process of –
a) Asexual reproduction
b) Meiosis
c) Mitosis
d) Binary fission
Answer: b

Question: Statement incorrect for law of dominance –
a) Characters are controlled by factors
b) Factors occur in pair and if contrasting then one will dominate and other is recessive
c) This law is used to explain the expression of parental characters in monohybrid cross (TT × tt), which is in 3:1 ratio in F1 and F2 generation
d) The genotype shown in F2 is 1:2:1
Answer: c

Question: A cross between F1 hybrid and a recessive parent (Tt × tt) gives a ratio of –
a) 1:1
b) 2:1
c) 3:1
d) 4:1
Answer: a

Question: How many phenotypes of blood groups are generated due to three alleles of gene for expressing sugar on RBC in a population?
a) 3
b) 6
c) 4
d) None of these
Answer: c

Question: Law of incomplete dominance was studied in –
a) Garden pea
b) Chick pea
c) Dog
d) Dog flower (snapdragon)
Answer: d

Question: Atall red-flowered pea plant after crossing with a dwarf white-flowered plant yields only tall red-flowered plants. A test cross shall give a ratio of –
a) 1 : 1
b) 3 : 1
c) 1 : 2 : 4 : 6 : 4 : 2 : 1
d) 1 : 1 : 1 : 1
Answer: d

Question: Self pollination of F2 generation dwarf plants produced by a monohybrid cross (TT × tt) –
a) Produced only dwarf plants (homozygous) in F3 and F4 generation
b) Produced only dwarf plants (heterozygous) in F3 and F4 generation
c) This concluded that genotype of dwarf in F2 was heterozygous
d) (a) and (c) are true
Answer: a

Question: In garden pea, round shape of seeds is dominant over wrinkled shape. A pea plant heterozygous for round shape of seed is selfed and 1600 seeds produced during the cross are subsequently germinated. How many seedlings would have the parental phenotype?
a) 400
b) 1600
c) 1200
d) 800
Answer: c

Question: Which of the following truly represents a heterozygous organism?
a) XXyy
b) RRYy
c) xxYY
d) RrYy
Answer: d

Question: If a cross between two individuals produces offspring with 50% dominant character(A) and 50% recessive character (a) the genotype of parents are
a) Aa, Aa
b) Aa, aa
c) AA, aa
d) AA, Aa
Answer: b

Question: A test cross enables one to
a) determine the viability of cross
b) distinguish between homozygous dominant and heterozygous dominant
c) determine whether two species can interbreed
d) determine the similarities in the DNA of two species
Answer: b

Question: The ratio 9 : 7 is produced due to –
a) complementary genes
b) supplementary genes
c) lethal genes
d) epistatic genes
Answer: b

Question: In Antirrhinum (Snapdragon), a red flower was crossed with a white flower and in F1 generation all pink flowers were obtained. When pink flowers were selfed, the F2 generation showed white, red and pink flowers. Choose the incorrect statements from the following.
a) Law of segregation does not apply in this experiment.
b) This experiment does not follow the Principle of Dominance.
c) Pink colour in F1 is due to incomplete dominance.
d) Ratio of F2 is 1:2:1 (red:pink:white)
Answer: a

Question: Mendel’s dihybrid ratio is
a) 15:1
b) 9:3:3:1
c) 1:2:1
d) 9:6:1
Answer: b

Question: Tritieale has been produced by intergeneric hybridization between
a) wheat and rye
b) wheat and rice
c) wheat and Aegilops
d) rice and maize
Answer: a

Question: An organism with two identical alleles is said to be –
a) hybrid
b) homozygous
c) heterozygous
d) dominant
Answer: b

Question: Some of the dominant traits studied by Mendel were
a) round seed shape, constricted pod shape and axial flower position
b) green pod colour, inflated pod shape and axial flower position
c) yellow seed colour, violet flower colour and yellow pod colour
d) axial flower position, green pod colour and green seed colour
Answer: b

Question: When red and white flowered Mirabilis plants are crossed all pink flowers are seen in F1 generation. When F1 progeny is selfed, the expected phenotypic and genotypic ratios are
a) 1:2:1 and 3:1:1
b) 3:1 and 1:2:1
c) 1:2:1 and 1:2:1
d) 1:1 and 1:1:1
Answer: c

Question: Mendel did not propose the theory of –
a) dominance
b) incomplete dominance
c) segregation
d) independent assortment
Answer: c