NEET Biology Principles of Inheritance and Variation MCQs Set 16

Multiple Choice Questions (MCQs) for NEET Biology: Principles of Inheritance and Variation

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Multiple Choice Questions

Question 1: Variations are :
(a) Degree by which progeny differs from their parents
(b) Degree by which progeny similar to their parents
(c) Process by which characters are passed on from parent to progeny
(d) True breeding lines
Show Answer & Explanation

Answer: (a) Degree by which progeny differs from their parents

Explanation:
1. Variations are the degree by which progeny differ from their parents.

Teacher's Note:
1. Mendel's laws: dominance (F1 shows only one parental trait), segregation (alleles separate during gamete formation, giving 3:1 in F2) and independent assortment (9:3:3:1 in a dihybrid cross).
2. Incomplete dominance gives an intermediate F1 (Mirabilis flower colour, 1:2:1 in F2); codominance expresses both alleles (ABO blood group IA and IB).

Question 2: Mendel found that the F1 always resembled either one of the parents and that the trait of the other parent was not seen in them. This is due to :
(a) Segregation
(b) Dominance
(c) Partial dominance
(d) Unit factor
Show Answer & Explanation

Answer: (b) Dominance

Explanation:
1. The appearance of only one parental trait in F1 is explained by dominance.

Teacher's Note:
1. The chromosomal theory of inheritance was proposed by Sutton and Boveri and later verified experimentally by Morgan using Drosophila; linked genes show recombination in proportion to their distance.
2. Sex determination: XY in humans and Drosophila (male heterogamety), XO in grasshopper, ZW in birds (female heterogamety).

Question 3: In monohybrid cross proportion of 3 : 1 explains:
(a) Dominance
(b) Segregation
(c) Both (1) and (2)
(d) Unit factor
Show Answer & Explanation

Answer: (c) Both (1) and (2)

Explanation:
1. The 3:1 phenotypic ratio in a monohybrid cross is explained by dominance and segregation.

Teacher's Note:
1. Mendel's laws: dominance (F1 shows only one parental trait), segregation (alleles separate during gamete formation, giving 3:1 in F2) and independent assortment (9:3:3:1 in a dihybrid cross).
2. Incomplete dominance gives an intermediate F1 (Mirabilis flower colour, 1:2:1 in F2); codominance expresses both alleles (ABO blood group IA and IB).

Question 4: It was found that sometimes the F 1 - had a phenotype that did not resemble either of the two parents and was in between the two. This is the case of :
(a) Dominance
(b) Incomplete dominance
(c) Codominance
(d) Pleiotropism
Show Answer & Explanation

Answer: (b) Incomplete dominance

Explanation:
1. When F1 is intermediate between the two parents it is incomplete dominance.

Teacher's Note:
1. The chromosomal theory of inheritance was proposed by Sutton and Boveri and later verified experimentally by Morgan using Drosophila; linked genes show recombination in proportion to their distance.
2. Sex determination: XY in humans and Drosophila (male heterogamety), XO in grasshopper, ZW in birds (female heterogamety).

Question 5: 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
Show Answer & Explanation

Answer: (a) Normal enzyme

Explanation:
1. A modified allele that still makes the normal enzyme behaves like the unmodified allele.

Teacher's Note:
1. Mendel's laws: dominance (F1 shows only one parental trait), segregation (alleles separate during gamete formation, giving 3:1 in F2) and independent assortment (9:3:3:1 in a dihybrid cross).
2. Incomplete dominance gives an intermediate F1 (Mirabilis flower colour, 1:2:1 in F2); codominance expresses both alleles (ABO blood group IA and IB).

Question 6: Recessive traits are seen due to :
(a) Formation of non functional enzyme
(b) Enzyme is not produced
(c) 1 and 2 both
(d) Formation of functional enzyme
Show Answer & Explanation

Answer: (c) 1 and 2 both

Explanation:
1. A recessive trait appears when the allele makes a non-functional enzyme or no enzyme at all.

Teacher's Note:
1. The chromosomal theory of inheritance was proposed by Sutton and Boveri and later verified experimentally by Morgan using Drosophila; linked genes show recombination in proportion to their distance.
2. Sex determination: XY in humans and Drosophila (male heterogamety), XO in grasshopper, ZW in birds (female heterogamety).

Question 7: Multiple alleles can be found only when :
(a) Population studies are made
(b) Individual study is made
(c) Mutation is absent
(d) Dominance is present
Show Answer & Explanation

Answer: (a) Population studies are made

Explanation:
1. Multiple alleles can be seen only when a population is studied, since an individual carries only two alleles.

Teacher's Note:
1. Mendelian disorders arise from single gene mutation (haemophilia, cystic fibrosis, sickle cell anaemia, phenylketonuria, thalassemia) while chromosomal disorders arise from numerical changes (Down's, Klinefelter's, Turner's).
2. Sickle cell anaemia is autosomal recessive and caused by a substitution of valine for glutamic acid at the sixth position of the beta globin chain.

Question 8: In Morgan's experiment, what will be percentage of recombination in case of body colour and eye colour in Drosophila ?
(a) 37.2%
(b) 1.3%
(c) 98.7%
(d) 37.2%
Show Answer & Explanation

Answer: (b) 1.3%

Explanation:
1. In Morgan's cross, yellow body and white eyes are tightly linked and recombinants were only 1.3 per cent.

Teacher's Note:
1. The chromosomal theory of inheritance was proposed by Sutton and Boveri and later verified experimentally by Morgan using Drosophila; linked genes show recombination in proportion to their distance.
2. Sex determination: XY in humans and Drosophila (male heterogamety), XO in grasshopper, ZW in birds (female heterogamety).

Question 9: Male heterogamety found in :
(a) Human
(b) Grasshopper
(c) Many birds
(d) 1 and 2 both
Show Answer & Explanation

Answer: (d) 1 and 2 both

Explanation:
1. Male heterogamety (XY or XO males) occurs in humans and grasshoppers.

Teacher's Note:
1. Mendelian disorders arise from single gene mutation (haemophilia, cystic fibrosis, sickle cell anaemia, phenylketonuria, thalassemia) while chromosomal disorders arise from numerical changes (Down's, Klinefelter's, Turner's).
2. Sickle cell anaemia is autosomal recessive and caused by a substitution of valine for glutamic acid at the sixth position of the beta globin chain.

Question 10: A diploid organism is heterozygous for 4 loci, how many types of gametes can be produced?
(a) 8
(b) 16
(c) 2
(d) 32
Show Answer & Explanation

Answer: (b) 16

Explanation:
1. A diploid heterozygous for four loci forms \(2^4 = 16\) types of gametes.

Teacher's Note:
1. Mendel's laws: dominance (F1 shows only one parental trait), segregation (alleles separate during gamete formation, giving 3:1 in F2) and independent assortment (9:3:3:1 in a dihybrid cross).
2. Incomplete dominance gives an intermediate F1 (Mirabilis flower colour, 1:2:1 in F2); codominance expresses both alleles (ABO blood group IA and IB).

Question 11: When a cross is made between tall plant with yellow seed (TtYy) and tall plant with green seed (Ttyy), what proportion of phenotype in the offspring could be expected to be tall and green.
(a) 25%
(b) 12.5%
(c) 37.5%
(d) 50%
Show Answer & Explanation

Answer: (c) 37.5%

Explanation:
1. TtYy x Ttyy gives tall in 3/4 of offspring and green seed in 1/2, so tall green is \(3/4 \times 1/2 = 37.5\) per cent.

Teacher's Note:
1. The chromosomal theory of inheritance was proposed by Sutton and Boveri and later verified experimentally by Morgan using Drosophila; linked genes show recombination in proportion to their distance.
2. Sex determination: XY in humans and Drosophila (male heterogamety), XO in grasshopper, ZW in birds (female heterogamety).

Question 12: In case of codominance :
(a) F1 - generation resembles both parents
(b) F1 - generation is in between both parents
(c) F 1- generation resembles either of the two parents
(d) All the above
Show Answer & Explanation

Answer: (a) F1 - generation resembles both parents

Explanation:
1. In codominance the F1 shows the traits of both parents (for example AB blood group).

Teacher's Note:
1. Mendelian disorders arise from single gene mutation (haemophilia, cystic fibrosis, sickle cell anaemia, phenylketonuria, thalassemia) while chromosomal disorders arise from numerical changes (Down's, Klinefelter's, Turner's).
2. Sickle cell anaemia is autosomal recessive and caused by a substitution of valine for glutamic acid at the sixth position of the beta globin chain.

Question 13: 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
Show Answer & Explanation

Answer: (a) Alternation or mutation in single gene

Explanation:
1. Mendelian disorders are caused by alteration or mutation in a single gene.

Teacher's Note:
1. Mendel's laws: dominance (F1 shows only one parental trait), segregation (alleles separate during gamete formation, giving 3:1 in F2) and independent assortment (9:3:3:1 in a dihybrid cross).
2. Incomplete dominance gives an intermediate F1 (Mirabilis flower colour, 1:2:1 in F2); codominance expresses both alleles (ABO blood group IA and IB).

Question 14: Which of the following characters of Drosophila make it NOT suitable for genetic studies?
(a) They can be grown on a simple synthetic medium in the laboratory.
(b) They complete their life cycle in about two weeks.
(c) A single mating produces only a few progeny flies.
(d) They have many types of hereditary variations that can be seen with a low power microscope.
(e) Male and female flies are not easily distinguishable.
(a) a, b, c
(b) a, b, c, d, e
(c) d and e
(d) c and e
Show Answer & Explanation

Answer: (d) c and e

Explanation:
1. Drosophila is suitable because a single mating gives a large number of progeny and the sexes are clearly distinguishable, so c and e are the unsuitable statements.

Teacher's Note:
1. The chromosomal theory of inheritance was proposed by Sutton and Boveri and later verified experimentally by Morgan using Drosophila; linked genes show recombination in proportion to their distance.
2. Sex determination: XY in humans and Drosophila (male heterogamety), XO in grasshopper, ZW in birds (female heterogamety).

Question 15: Incomplete dominance can be seen in :
(a) Flower colour in Mirabilis jalapa
(b) Flower colour in Pisum sativum
(c) Size of starch grains in pea
(d) 1 and 3 both
Show Answer & Explanation

Answer: (d) 1 and 3 both

Explanation:
1. Flower colour in Mirabilis and starch grain size in pea both show incomplete dominance.

Teacher's Note:
1. Mendelian disorders arise from single gene mutation (haemophilia, cystic fibrosis, sickle cell anaemia, phenylketonuria, thalassemia) while chromosomal disorders arise from numerical changes (Down's, Klinefelter's, Turner's).
2. Sickle cell anaemia is autosomal recessive and caused by a substitution of valine for glutamic acid at the sixth position of the beta globin chain.

Question 16: Which of the following was/were applied first time to problems in biology during Mendel's investigations into inheritance
(a) Statistical analysis
(b) Mathematical logic
(c) Computational devices
(d) Both 1 and 2
Show Answer & Explanation

Answer: (d) Both 1 and 2

Explanation:
1. Mendel was the first to apply statistical analysis and mathematical logic to problems in biology.

Teacher's Note:
1. Mendel's laws: dominance (F1 shows only one parental trait), segregation (alleles separate during gamete formation, giving 3:1 in F2) and independent assortment (9:3:3:1 in a dihybrid cross).
2. Incomplete dominance gives an intermediate F1 (Mirabilis flower colour, 1:2:1 in F2); codominance expresses both alleles (ABO blood group IA and IB).

Question 17: A true breeding line is that
(a) Having undergone continuous cross pollination
(b) Having undergone continuous self pollination
(c) Having undergone continuous vegetative propagation
(d) Obtain through tissue culture (Meristem)
Show Answer & Explanation

Answer: (b) Having undergone continuous self pollination

Explanation:
1. A true breeding line has undergone continuous self pollination and shows stable trait inheritance.

Teacher's Note:
1. The chromosomal theory of inheritance was proposed by Sutton and Boveri and later verified experimentally by Morgan using Drosophila; linked genes show recombination in proportion to their distance.
2. Sex determination: XY in humans and Drosophila (male heterogamety), XO in grasshopper, ZW in birds (female heterogamety).

Question 18: How many true breeding pea plant varieties were selected by Mendel
(a) 7
(b) 14
(c) 21
(d) 28
Show Answer & Explanation

Answer: (b) 14

Explanation:
1. Mendel selected 14 true breeding pea varieties (seven contrasting pairs).

Teacher's Note:
1. Mendelian disorders arise from single gene mutation (haemophilia, cystic fibrosis, sickle cell anaemia, phenylketonuria, thalassemia) while chromosomal disorders arise from numerical changes (Down's, Klinefelter's, Turner's).
2. Sickle cell anaemia is autosomal recessive and caused by a substitution of valine for glutamic acid at the sixth position of the beta globin chain.

Question 19: Regarding to pair of dominant and recessive trait which of the following combination is wrong
(a) Flower colour – Violet / white
(b) Flower position – Axial / terminal
(c) Pod shape – Inflated / constricted
(d) Seed colour – Green / yellow
Show Answer & Explanation

Answer: (d) Seed colour – Green / yellow

Explanation:
1. Yellow seed colour is dominant and green recessive, so the pair 'green / yellow' is given the wrong way round.

Teacher's Note:
1. Mendel's laws: dominance (F1 shows only one parental trait), segregation (alleles separate during gamete formation, giving 3:1 in F2) and independent assortment (9:3:3:1 in a dihybrid cross).
2. Incomplete dominance gives an intermediate F1 (Mirabilis flower colour, 1:2:1 in F2); codominance expresses both alleles (ABO blood group IA and IB).

Question 20: If F1 individual of genotype (Tt) go through sexual reproduction, then it's gamete (pollengrain) with genotype (T) have what chances to pollinate eggs of the genotype (T)
(a) 25 %
(b) 50 %
(c) 75 %
(d) 100 %
Show Answer & Explanation

Answer: (b) 50 %

Explanation:
1. A Tt plant forms T and t gametes in equal numbers, so the chance is 50 per cent.

Teacher's Note:
1. Mendel's laws: dominance (F1 shows only one parental trait), segregation (alleles separate during gamete formation, giving 3:1 in F2) and independent assortment (9:3:3:1 in a dihybrid cross).
2. Incomplete dominance gives an intermediate F1 (Mirabilis flower colour, 1:2:1 in F2); codominance expresses both alleles (ABO blood group IA and IB).

Question 21: The fact that the alleles donot show any blending and that both the characters are recovered as such in F2 generation, become the basis of
(a) Law of Dominance
(b) Law of paired factors
(c) Law of segregation
(d) Law of independent assortment
Show Answer & Explanation

Answer: (c) Law of segregation

Explanation:
1. The lack of blending and recovery of both characters in F2 is the basis of the law of segregation.

Teacher's Note:
1. Mendelian disorders arise from single gene mutation (haemophilia, cystic fibrosis, sickle cell anaemia, phenylketonuria, thalassemia) while chromosomal disorders arise from numerical changes (Down's, Klinefelter's, Turner's).
2. Sickle cell anaemia is autosomal recessive and caused by a substitution of valine for glutamic acid at the sixth position of the beta globin chain.

Question 22: 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
Show Answer & Explanation

Answer: (d) Either 2 or 3

Explanation:
1. A recessive trait results when either a non-functional enzyme or no enzyme is produced.

Teacher's Note:
1. Mendel's laws: dominance (F1 shows only one parental trait), segregation (alleles separate during gamete formation, giving 3:1 in F2) and independent assortment (9:3:3:1 in a dihybrid cross).
2. Incomplete dominance gives an intermediate F1 (Mirabilis flower colour, 1:2:1 in F2); codominance expresses both alleles (ABO blood group IA and IB).

Question 23: Genes responsible for ABO blood group determines which of the following biomolecules of RBC plasma membrane
(a) Phospholipid
(b) Proteins
(c) Sugars
(d) Cholesteroles
Show Answer & Explanation

Answer: (c) Sugars

Explanation:
1. The ABO genes control the type of sugar polymer on the surface of red blood cells.

Teacher's Note:
1. The chromosomal theory of inheritance was proposed by Sutton and Boveri and later verified experimentally by Morgan using Drosophila; linked genes show recombination in proportion to their distance.
2. Sex determination: XY in humans and Drosophila (male heterogamety), XO in grasshopper, ZW in birds (female heterogamety).

Question 24: If there are four allelic forms for the gene controlling ABO blood group then what will be the number of possible genotypes
(a) 6
(b) 10
(c) 12
(d) 14
Show Answer & Explanation

Answer: (b) 10

Explanation:
1. Four alleles give \(n(n+1)/2 = 10\) possible genotypes.

Teacher's Note:
1. Mendelian disorders arise from single gene mutation (haemophilia, cystic fibrosis, sickle cell anaemia, phenylketonuria, thalassemia) while chromosomal disorders arise from numerical changes (Down's, Klinefelter's, Turner's).
2. Sickle cell anaemia is autosomal recessive and caused by a substitution of valine for glutamic acid at the sixth position of the beta globin chain.

Question 25: Multiple alleles can be found during study of
(a) Gametes
(b) Individual
(c) Population
(d) All above
Show Answer & Explanation

Answer: (c) Population

Explanation:
1. Multiple alleles are found when a population is studied.

Teacher's Note:
1. Mendel's laws: dominance (F1 shows only one parental trait), segregation (alleles separate during gamete formation, giving 3:1 in F2) and independent assortment (9:3:3:1 in a dihybrid cross).
2. Incomplete dominance gives an intermediate F1 (Mirabilis flower colour, 1:2:1 in F2); codominance expresses both alleles (ABO blood group IA and IB).

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