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

Question: ABO blood group system is due to
a) multifactor inheritance
b) incomplete dominance
c) multiple allelism
d) epistasis
Answer: c

Question: The distance between the genes is measured by
a) angstrom
b) map unit
c) Dobson unit
d) millimetre
Answer: b

Question: Which of the following is not a Mendelian disorder
a) Haemophilia
b) Cystic fibrosis
c) Cryduchat syndrome
d) Sickle cell anaemia
Answer: c

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

Question: Chromosomal aberrations are commonly observed in
a) Germinal cells
b) Cancer cells
c) Nail base cells
d) Gametes
Answer: b

Question: The ratio of phenotypes in F2 of a monohybrid cross is
a) 3 : 1
b) 1 : 2 : 1
c) 9 : 3 : 3 : 1
d) 2 : 1
Answer: a

Question: Who among the following used the frequency of recombination between gene pairs on the same chromosome as a measure of distance between genes and mapped their position
a) Davenport
b) Sturtevant
c) Morgan
d) Nillson
Answer: b

Question: Genetic disorders determined by alteration or mutation in single gene are known as
a) Chromosomal disorders
b) Mendelian disorders
c) Non inheritable disorders
d) All above
Answer: b

Question: Distance between the genes and percentage of recombination shows
a) a direct relationship
b) an inverse relationship
c) a parallel relationship
d) no relationship
Answer: a

Question: In some insects half of the sperms possess X chromosome along with autosomes while half of the sperms carries
a) Only autosomes
b) y chromosome along with autosome
c) x chromosome only
d) x chromosome along with autosomes
Answer: a

Question: Retarted physical, psychomotor and mental development are consequences observed during
a) Down’s syndrome
b) Klinefelter’s syndrome
c) Turner’s syndrome
d) Lesch nyhan syndrome
Answer: a

Question: The crossing of F1 to homozygous recessive parent is called
a) back cross
b) test cross
c) F1 cross
d) all of these
Answer: b

Question: Which of the following structure was discovered by Henking
a) y-body
b) Bar body
c) x-body
d) Nu-body
Answer: c

Question: Drosophila melanogaster is best material for study of inheritance. Which of the following reason is not appropriate for selection of Drosophila
a) They can grow on simple synthetic medium
b) They complete their life cycle in about two weeks
c) Single mating could produce small number of progeny
d) Clear differentiation of the sexes
Answer: c

Question: Regarding to phenylketonuria which of the following statement is wrong
a) Phenylalanine can not convert into tyrosine
b) Phenylalanine convert into phenylpyruvate and derivatives
c) Phenylpyruvate deposited in heart, liver and kidney
d) This is inborn error of metabolism
Answer: c

Question: The monohybrid genotypic ratio 1 : 2 : 1 in F2 generation indicates
a) segregation
b) independent assortment
c) dominance
d) incomplete dominance
Answer: a

Question: A pure tall pea was crossed with a pure dwarf pea. All the plants of F1 were found to be tall. This is due to
a) law of dominance
b) disappearance of factor for dwarfness in F1 generation
c) segregation of factors
d) co-ordination
Answer: a

Question: Which of the following crosses would produce a genotypic ratio of 1 : 2 : 1 in F2
a) AB × AB
b) Ab × ab
c) Ab × Ab
d) ab × ab
Answer: c

Question: If yellow body, white eyed drosophila is crossed with wild brown body red eyes drosophila. Then what would be frequency of recombinants in F1 generation
a) 100 %
b) 1.3 %
c) 98.7 %
d) 0 %
Answer: d

Question: In this given pedigree what is the mode of inheritance
a) Autosomal dominant
b) Autosomal recessive
c) X-linked dominant
d) X-linked recessive
Answer: b

Question: Which Mendelian idea is depicted by a cross in which the F1 generation resembles both the parents?
a) Law of dominance
b) Inheritance of one gene
c) Co-dominance
d) Incomplete dominance
Answer: c

Question: Extra chromosome ‘X’ is present in which one of the following cases?
a) Down syndrome
b) Klinefelter syndrome
c) Turner syndrome
d) Bleeder’s disease
Answer: b

Question: Sex is determined in human beings
a) by ovum
b) at time of fertilization
c) 40 days after fertilization
d) seventh to eight week when genitals differentiate in foetus
Answer: b

Question: A character which is expressed in a hybrid is called
a) dominant
b) recessive
c) co-dominant
d) epistatic
Answer: a

Question: In a dihybrid cross, F2 phenotypic ratio is 13 : 3. It is case of
a) complementary genes
b) epistatic genes
c) multigenic inheritance
d) incomplete dominance
Answer: b

Question: Mental retardation in man associated with sex chromosomal abnormality is usually due to
a) increase in size of X-chromosome
b) increase in size of Y-chromosome
c) increase in number of Y-chromosome
d) increase in number of X-chromosome
Answer: d

Question: It is well known that Queen Victoria of England was a carrier for haemophilia. Since this is an X-linked disease, it can be predicted that
a) all of her sons would have had disease
b) her daughters would have been carriers
c) her father must definitely have had haemophilia
d) haemophilia would have occurred in more of her male than her female descendents
Answer: d

Question: Sickle cell anaemia is
a) caused by substitution of valine by glutamic acid in the beta globin chain of haemoglobin
b) caused by a change in a single base pair of DNA
c) characterized by elongated sickle like RBCs with a nucleus
d) an autosomal linked dominant trait
Answer: b

Assertion/Reason Statement Type Questions
In the following questions, a statement of Assertion is followed by a statement of Reason.
(a) If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.
(b) If both Assertion and Reason are true but the Reason is not the correct explanation of the Assertion.
(c) If Assertion is true but Reason is false.
(d) If both Assertion and Reason are false.

Question: Assertion : The genetic component of an organism is called genotype.
Reason : Genotype is the type of hereditary properties of an organism.
Answer: a

Question: Assertion : Persons suffering from haemophilia fail to produce blood clotting factor VIII.
Reason : Prothrombin producing platelets in such persons are found in very low concentration.
Answer: c

Question: Assertion : Mendel’s law are able to predict accurately the pattern of inheritance for a situation in which alleles show the complete dominance.
Reason : Effect of environment, other alleles did not explained by the Mendel.
Answer: b

Critical Thinking Type Questions

Question: What is the probability of production of dwarf offsprings in a cross between two heterozygous tall pea plants?
a) Zero
b) 50%
c) 25%
d) 100%
Answer: c

Question: A gene is said to be dominant if
a) it expresses its effect only in homozygous state.
b) it expresses its effect only in heterozygous condition.
c) it expresses its effect both in homozygous and heterozygous condition.
d) it never expresses its effect in any conditions.
Answer: c

Question: A mutation is a
a) sudden temporary change in an organism’s genetic material.
b) change in phenotype followed by a change in genotype.
c) change in hereditary material directed by a changing environment.
d) change in genotype which may result in a new expression of a characteristic.
Answer: d

Question: In case of codominance, the offsprings of F1 generation have the trait
a) of either of two parents.
b) of both the parents.
c) of none of the parents.
d) in between the traits of two parents.
Answer: b

Question: What can be the blood group of offspring when both parents have AB blood group?
a) AB only
b) A, B and AB
c) A, B, AB and O
d) A and B only
Answer: b

Question: The law of segregation of characters is also called the law of purity of gametes because
a) gametes have only one of the two alleles for each character.
b) gametes cannot be contaminated.
c) both (a) and (b)
d) gametes are very different type of cells.
Answer: a

Question: In Down’s syndrome, karyotyping has shown that the disorder is associated with trisomy of chromosome number 21 usually due to
a) non-disjunction during egg formation.
b) non-disjunction during sperm cell formation.
c) addition of extra chromosome during cleavage of zygote.
d) non-disjunction during egg cells production and sperm production.
Answer: a

Question: A tobacco plant heterozygous for albinism (a recessive character) is self-pollinated and 1200 seeds are subsequently germinated. How many seedlings would have the parental genotype?
a) 1250
b) 600
c) 300
d) 2250
Answer: b

Question: In Drosophila, the sex is determined by
a) the ratio of pairs of X-chromosomes to the pairs of autosomes.
b) whether the egg is fertilized or develops parthenogenetically.
c) the ratio of number of X-chromosomes to the sets of autosomes.
d) X and Y-chromosomes.
Answer: a

Question: The law of segregation of characters postulated by Mendel can be related to
a) the presence of two genes for each character in a somatic cell.
b) a gamete receiving only one of the two homologous chromosomes during meiosis.
c) presence of both genes on the same chromosome.
d) None of the above
Answer: b

Question: Regarding ABO blood group, if one parent is homozygous and other is heterozygous, what are the chances that their child will have ‘O’ blood group?
a) 25%
b) 50%
c) 75%
d) Zero
Answer: b

Question: What proportion of the offsprings obtained from cross AABBCC × AaBbCc will be completely heterozygous for all genes segregated independently?
a) 1/8
b) 1/4
c) 1/2
d) 1/16
Answer: a

Question: Down’s syndrome is caused by an extra copy of chromosome number 21. What percentage of offspring produced by an affected mother and a normal father?
a) 50%
b) 25%
c) 100%
d) 75%
Answer: a

Question: Why is the allele for wrinkled seed shape in garden peas considered recessive?
a) It “recedes” in the F2 generation when homozygous parents are crossed.
b) The trait associated with the allele is not expressed in heterozygotes.
c) Individuals with the allele have lower fitness than that of individuals with the dominant allele.
d) The allele is less common than the dominant allele.
Answer: b

Question: In Mendel’s experiments with garden pea, round seed shape (RR) was dominant over wrinkled seeds (rr), yellow cotyledon (YY) was dominant over green cotyledon (yy). What are the expected phenotypes in the F2 generation of the cross RRYY × rryy?
a) Only wrinkled seeds with green cotyledons.
b) Only wrinkled seeds with yellow cotyledons.
c) Only round seeds with yellow cotyledons.
d) Round seeds with yellow cotyledons and wrinkled seeds with green cotyledons.
Answer: d

Question: Mendel’s rules do not correctly predict patterns of inheritance for tightly linked genes or the inheritance of alleles that show incomplete dominance or epistasis. Does this mean that his hypotheses are incorrect?
a) Yes, because they are relevant to only a small number of organisms and traits.
b) Yes, because not all data support his hypotheses.
c) No, because he was not aware of meiosis or the chromosome theory of inheritance.
d) No, it just means that his hypotheses are limited to certain conditions.
Answer: d