Worksheets Class 12 Biology Principles of Inheritance and Variation

Students should refer to Worksheets Class 12 Biology Principles of Inheritance and Variation Chapter 5 provided below with important questions and answers. These important questions with solutions for Chapter 5 Principles of Inheritance and Variation have been prepared by expert teachers for Class 12 Biology based on the expected pattern of questions in the class 12 exams. We have provided Worksheets for Class 12 Biology for all chapters on our website. You should carefully learn all the important examinations questions provided below as they will help you to get better marks in your class tests and exams.

Principles of Inheritance and Variation Worksheets Class 12 Biology

Question. In monohybrid cross proportion of 3 : 1 explains:
(a) Dominance
(b) Segregation
(c) Both (a) and (b)
(d) Unit factor 

Question. The modified allele is equivalent to the unmodified allele when it produces :
(a) Normal enzyme
(b) A non functional enzyme
(c) No enzyme at all
(d) Inactive enzyme

Question. Dominance of any character generally depends on
(a) Gene or product related informations of any gene
(b) Character choosen by ourself in study
(c) Environmental factors
(d) Both 1 and 2

Question. Mandel published his work in 1865 but it remained unrecognised till 1900. Which of the following reason was not responsible for it
(a) Communication was not easy
(b) His concept of genes (factors) as stable and discrete unit was not accepted by hiscontemporaries as an explanation for apparently continuous variations
(c) Use of mathematics to explain biological phenomenon
(d) Use of emasculation technique

Question. Parallelism between charomosome and behaviour of gene was established by
(a) de Vries, Correns and Tschermark
(b) Sutton and Boveri
(c) Bateson and Punnet
(d) Landsteiner and de Castello

Question. Chromosomal disorders arise due to
(a) Absence of one or more chromosomes
(b) Excess of one or more chromosomes
(c) Abnormal arrangement of one or more chromosomes
(d) All the above

Question. Which of the following symptom is not assocoated with Down’s syndrome
(a) Flat back of head
(b) Many loops on finger tips
(c) Big and wrinked tongue
(d) Congenital liver diseases

Question. Who among the following united the knowledge of chromosomal segregation with Mendelian principles and called it chromosomal theory of inheritance
(a) Bateson
(b) Boveri
(c) Sutton
(d) Correns

Question. Segregation of alleles is a random process so what would be the chances of a gamete containing either alleles
(a) 25 %
(b) 50 %
(c) 75 %
(d) 100 %

Question. In a large number of insects the mechanism of sex determination is of :
(a) XO type
(b) XY type
(c) ZW type
(d) All the above

Question. Male heterogamety found in :
(a) Human
(b) Grasshopper
(c) Many birds
(d) 1 and 2 both

Question. Graphical representation to calculate the probability of all possible genotypes of offspring in a genetic cross, is known as
(a) Mendel square
(b) Punnett square
(c) Crossboard method
(d) Emasculation method

Question. Polymerisation of mutant haemoglobin molecule in sickle cell anaemia is due to
(a) Sulphadrugs
(b) High oxygen
(c) Low oxygen concentration
(d) Plasmodium falciperum

Question. Female heterogamety can be seen is
(a) Human beings
(b) Drosophilla
(c) Hen
(d) Honey bees

Question. In case of codominance :
(a) F₁ – generation resembles both parents
(b) F₁ – generation is in between both parents
(c) F₁– generation resembles either of the two parents
(d) All the above

Question. Mendelian disorder are mainly determined by :
(a) Alternation or mutation in single gene
(b) Absence of one chromosome
(c) Excess of one of more chromosome
(d) All the above

Question. In the theoritical explanation of allelic interaction for dominant and recessive forms, the recessive trait is seen due to production of
(a) Normal enzyme
(b) A non functional enzyme
(c) No enzyme production
(d) Either 2 or 3

Question. Genes responsible for ABO blood group determines which of the following biomolecules of RBC plasma membrane
(a) Phospholipid
(b) Proteins
(c) Sugars
(d) Cholesteroles

Question. Gynaecomastia state can be seen in
(a) Down’s syndrome
(b) Klinefelter’s syndrome
(c) Turner syndrome
(d) Edward’s syndrome

Question. Experimental verification of chromosomal theory of inheitance was proposed by
(a) Tschermark
(b) de Vries
(c) Sutton
(d) Morgan

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

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

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 %

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

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

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

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

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

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

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

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

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

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

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.

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

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

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

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

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

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

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.

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

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.

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 daugthers 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.

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

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.

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

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

Statement Type Questions Class 12 Biology Principles of Inheritance and Variation

Question. Which one of the following cannot be explained on the basis of Mendel’s law of dominance?
(a) The discrete unit controlling a particular character is called a factor.
(b) Out of one pair of factors’ one is dominant and the other is recessive.
(c) Alleles do not show any blending and both the characters recover as such in F₂ generation.
(d) Factors occur in pairs.

Question. Which one of the following conditions correctly describes the manner of determining the sex in the given example?
(a) Homozygous sex chromosomes (ZZ) determine female sex in birds.
(b) XO type of sex chromosomes determine male sex in grasshopper.
(c) XO condition in human as found in Turner’s syndrome, determines female sex.
(d) Homozygous sex chromosomes (XX) produce male in Drosophila.

Question. Which of the following statement is not correct of two genes that show 50% recombination frequency?
(a) The genes are tightly linked.
(b) The genes show independent assortment.
(c) If the genes are present on the same chromosome, they undergo more than one crossovers in every
meiosis.
(d) The genes may be on different chromosomes.

Question. Which of the following is incorrect regarding ZW-ZZ type of sex determination?
(a) It occcurs in birds and some reptiles
(b) Females are homogametic and males are heterogametic
(c) 1 : 1 sex ratio is produced in the offsprings
(d) All of these

Question. Which of the following statements are correct?
(i) Haemophilia is a sex-linked recessive disease.
(ii) Down’s syndrome is due to aneuploidy.
(iii) Phenylketonuria is an autosomal dominant gene disorder.
(iv) Phenylketonuria is an autosomal recessive gene disorder.
(v) Sickle-cell anaemia is an X-linked recessive gene disorder.
(a) (i), (iii) and (v)
(b) (i) and (iii)
(c) (ii) and (v)
(d) (i), (ii) and (iv)

Question. Which of the following statements are the correct?
(i) Failure of segregation of chromatids during cell division results in aneuploidy.
(ii) Chromosomal disorders are mainly determined by alteration or mutation in a single gene.
(iii) Thalasemia and cystic fibrosis are Mendelian disorders.
(iv) Sickle cell anemia is an X-linked trait.
(v) Haemophilia is an autosome linked recessive disease.
(a) (i) and (iii)
(b) (i), (iii) and (iv)
(c) (iii) and (iv)
(d) (ii) and (iii)

Assertion/Reason Statement Type Questions Class 12 Biology Principles of Inheritance and Variation

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.

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.

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.

Matching Type Questions Class 12 Biology Principles of Inheritance and Variation

Question. Match column-I with column-II and select the correct answer using the codes given below.

Column-I	Column-II
A. Turner syndrome	I. Trisomy
B. Linkage	II. AA + XO
C. Y-chromosome	III. Morgan
D. Down’s syndrome	IV. Testis determining factor

(a) A – II; B – I; C – IV; D – III
(b) A – II; B – I; C – IV; D – III
(c) A – IV; B – II; C – I; D – III
(d) A – II; B – III; C – IV; D – I

Question. Match the column-I with column-II and choose the correct option.

Column -I	Column -II
A. Incomplete dominance	I. Drosophila
B. Mendelian disorder	II. Antirrhinum sp.
C. Transforming principle	III. Griffith
D. Dihybrid cross	IV. Haemophilia

(a) A – I; B – IV; C – III; D – II
(b) A – IV; B – II; C – III; D – I
(c) A – II; B – III; C – IV; D – I
(d) A – II; B – IV; C – III; D – I

Question. Match the symbols used in human pedigree analysis (given in column-I) with their name (given in column-II) and choose the correct option.

(a) A – III, B – I, C – II, D – V, E – IV
(b) A – II, B – I, C – VI, D – III, E – IV
(c) A – III, B – IV, C – I, D – V, E – II
(d) A – III, B – I, C – VI, D – V, E – IV

Question. Match column-I (Definition) with column-II (Terms) and select the correct option from the codes given below.

Column-I (Definition)	Column-II (Terms)
A. A single trait	I. Pleiotropy controlled by three or more than three alleles
B. A single trait	II. Multiple alleles controlled by three or more than three genes
C. A single gene	III. Polygenic inheritance exhibits multiple phenotypic expression

(a) A – II; B – III; C – I
(b) A – III; B – II; C – I
(c) A – I; B – II; C – III
(d) A – II; B – I; C – III

Diagram Type Questions Class 12 Biology Principles of Inheritance and Variation

Question. Which one of the following symbols and its representation, used in human pedigree analysis is correct?

Question. The given figure is a highly simplified representation of the human sex chromosomes from a karyotype. The gene a and b could be of Gene a Gene b

(a) colour blindness and body height.
(b) attached ear lobe and Rhesus blood group.
(c) haemophilia and red-green colour blindness.
(d) phenylketonuria and haemophilia.

Question. Study the pedigree chart of a certain family given below and select the correct conclusion which can be drawn for the character.

(a) The female parent is heterozygous.
(b) The parents could not have had a normal daughterfor this character.
(c) The trait under study could not be colourblindness.
(d) The male parent is homozygous dominant.

Question. Following is a pedigree for albinism (aa). What is the probability of II -1 to be a heterozygous ?

(a) 1/3
(b) 1/2
(c) 2/3
(d) 1/4

Critical Thinking Type Questions Class 12 Biology Principles of Inheritance and Variation

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.

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%

Question. What can be the blood group of offfspring when bothb parents have AB blood group?
(a) AB only
(b) A, B and AB
(c) A, B, AB and O
(d) A and B only

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.

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

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 extrachromosome during cleavage of zygote.
(d) non-disjunction during egg cells production and sperm production.

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

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

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

Question. What proportion of the offsprings obtaied from cross AABBCC × AaBbCc will be completely heterozygous for all genes segregated indpendently?
(a) 1/8
(b) 1/4
(c) 1/2
(d) 1/16

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.

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.

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 RR YY × rryy ?
(a) Only wrinkled seeds with green cotyledons.
(b) Only wrinkled seeds with both yellow cotyledons.
(c) Only round seeds with yellow cotyledons.
(d) Round seeds with yellow cotyledons and wrinkled seeds with green cotyledons.

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.

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.
(The wrinkled allele is a rare mutant).

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 hypothesis 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 hypothesis.
(c) No, because he was not aware of meiosis or the chromosome theory of inheritance.
(d) No, it just means that his hypothesis are limited to certain conditions.