Class 12 Anthropology Chapter 2 Genetics Solutions

Class 12 Anthropology Chapter 2 Genetics Solutions with complete textual questions and answers, important additional exam-oriented questions and answers, and easy-to-understand solutions for effective exam preparation.

Class 12 Anthropology Chapter 2 Genetics Solutions

Textual Questions & Answers

1. Who is the father of modern genetics?

Ans: The father of modern genetics is Gregor Johann Mendel.

2. What is heredity?

Ans: Heredity is the transmission of genetic characteristics or traits from parents to their offspring through genes.

3. For how many years Mendel carried out his experiment?

Ans: Mendel conducted his experiments on pea plants for about eight years, from 1856 to 1863.

4. Where Mendel published his result?

Ans: Mendel presented the results of his experiments to the Natural Science Society of Brünn in 1865. His paper, “Experiments on Plant Hybridization,” was published in the proceedings of the society in 1866.

5. Who rediscovered Mendel laws of inheritance?

Ans: Mendel’s laws of inheritance were independently rediscovered around 1900 by Hugo de Vries, Carl Correns, and Erich von Tschermak.

6. What is Mendel’s monohybrid ratio?

Ans: Mendel’s monohybrid ratio is obtained when the inheritance of one pair of contrasting traits is studied. In a typical cross, a pure-breeding tall pea plant (TT) is crossed with a pure-breeding dwarf pea plant (tt). All the plants in the F₁ generation are tall (Tt). When the F₁ plants are self-pollinated, the F₂ generation shows a phenotypic ratio of 3 tall : 1 dwarf and a genotypic ratio of 1 TT : 2 Tt : 1 tt.

7. What is gene?

Ans: A gene is a basic unit of heredity. It is a specific sequence of DNA that contains information for a functional product, usually a protein or a functional RNA molecule. Genes are located at specific positions, called loci, on chromosomes.

8. What is Mendel’s dihybrid ratio?

Ans: Mendel’s dihybrid ratio is the phenotypic ratio obtained when two pairs of contrasting traits are studied simultaneously. In the classic dihybrid cross, the F₂ generation shows a phenotypic ratio of 9 round yellow : 3 round green : 3 wrinkled yellow : 1 wrinkled green, or 9:3:3:1. This ratio is observed under the conditions of Mendel’s classic experiment and illustrates independent assortment.

9. What is eugenics?

Ans: Eugenics is a historical movement and set of ideas that attempted to influence the genetic composition of human populations through selective reproduction. It included attempts to encourage reproduction among people considered to have desirable traits and to restrict reproduction among people considered to have undesirable traits. Eugenics has been associated with coercive practices, discrimination, and serious ethical problems.

10. Who is the father of eugenics?

Ans: Sir Francis Galton is generally regarded as the founder or “father” of eugenics. He coined the term “eugenics” in 1883.

11. What are the two types of eugenics?

Ans: The two commonly described historical forms of eugenics are positive eugenics and negative eugenics. Positive eugenics encouraged reproduction among people considered to have desirable traits, whereas negative eugenics sought to restrict reproduction among people considered to have undesirable traits.

12. What is another name for down syndrome?

Ans: Down syndrome is also known as trisomy 21 because it is usually caused by the presence of an extra copy of chromosome 21. The older term “Mongolism” is obsolete and should not be used.

13. What is the number of chromosomes in a female having Turner syndrome?

Ans: A person with the classic form of Turner syndrome has 45 chromosomes. The typical karyotype is 45,X, meaning that there is only one X chromosome instead of the usual two sex chromosomes. Some individuals have mosaic or other chromosomal forms of Turner syndrome.

14. Who discovered Klinefelter syndrome?

Ans: Klinefelter syndrome was first described in 1942 by Dr. Harry F. Klinefelter and his colleagues. It is most commonly associated with an additional X chromosome, resulting in a 47,XXY karyotype.

15. Write a short note on down syndrome.

Ans: Down syndrome is a genetic condition usually caused by an extra copy of chromosome 21 and is therefore also known as trisomy 21. It was first described clinically by the British physician John Langdon Down in 1866. Common features may include characteristic facial features, short stature, reduced muscle tone, and varying degrees of intellectual disability. The condition is also associated with an increased risk of certain medical conditions. In the most common form, affected individuals have 47 chromosomes, including three copies of chromosome 21.

16. Write a short notes on:

(a) Turner syndrome.

Ans: Turner syndrome is a chromosomal condition that affects females and is usually caused by the complete or partial absence of one X chromosome. The classic form has the karyotype 45,X, giving a total of 45 chromosomes instead of the usual 46. Common features include short stature, ovarian insufficiency, and infertility. Other features may include a webbed neck and certain heart and kidney abnormalities. Turner syndrome may also occur in mosaic forms.

(b) Klinefelter syndrome.

Ans: Klinefelter syndrome is a chromosomal condition that affects males and is most commonly associated with an additional X chromosome, resulting in a 47,XXY karyotype. Harry F. Klinefelter and his colleagues first described it in 1942. Individuals may have small testes, reduced testosterone production, infertility, sparse facial and body hair, and, in some cases, breast development. The features vary among individuals.

(c) Eugenics.

Ans: Eugenics is a historical movement that attempted to influence human reproduction to alter the genetic characteristics of future generations. Sir Francis Galton coined the term “eugenics” in 1883. Historically, eugenic ideas included attempts to encourage reproduction among people considered to have desirable characteristics and to restrict reproduction among people considered to have undesirable characteristics. Many such practices were coercive and discriminatory, and eugenics is now regarded as scientifically problematic and ethically unacceptable.

(d) Gene and allele.

Ans: A gene is a segment of DNA that contains information for a functional product and contributes to the expression of a particular characteristic. An allele is one of two or more alternative forms of a gene at the same locus on homologous chromosomes. For example, T and t may represent two different alleles of the gene controlling plant height in Mendel’s pea plants. In a diploid organism, an individual normally has two alleles for each autosomal gene, one inherited from each parent.

(e) Genotype and phenotype.

Ans: Genotype refers to the genetic constitution or allele combination of an organism for one or more traits. Phenotype refers to the observable characteristics of an organism, which result from the interaction of its genotype with environmental factors. For example, TT and Tt are different genotypes, while both may produce the tall phenotype when T is dominant over t.

(f) Homozygous and heterogeneous.

Ans: Homozygous and heterozygous are terms used to describe the two alleles of a particular gene in a diploid organism. An individual is homozygous when the two alleles are identical, such as TT or tt. An individual is heterozygous when the two alleles are different, such as Tt. In a simple Mendelian system with complete dominance, the dominant allele is expressed in a heterozygous individual.

17. Describe Mendel’s monohybrid ratio with a neat diagram.

Ans: Mendel studied the inheritance of contrasting traits in garden pea plants (Pisum sativum). In one of his experiments, he studied plant height by crossing a pure-breeding tall plant with a pure-breeding dwarf plant.

The cross can be represented as follows:

Parental generation (P):

TT × tt

Tall × Dwarf

Gametes:

T and t

F₁ generation:

Tt, Tt, Tt, Tt

All F₁ plants are tall.

The F₁ plants were then self-pollinated:

Tt × Tt

The Punnett square is:

	T	t
T	TT	Tt
t	Tt	tt

F₂ generation:

TT : Tt : Tt : tt

Genotypic ratio:

1 TT : 2 Tt : 1 tt

Phenotypic ratio:

3 Tall : 1 Dwarf

Thus, the monohybrid phenotypic ratio is 3:1, while the genotypic ratio is 1:2:1.

This experiment demonstrates Mendel’s Law of Segregation, according to which the two alleles of a gene separate during the formation of gametes.

18. Describe Mendel’s dihybrid ratio.

Ans: Mendel studied the inheritance of two pairs of contrasting traits simultaneously in a dihybrid cross. In his classic experiment, he crossed pea plants having round, yellow seeds with plants having wrinkled, green seeds.

Parental generation (P):

RRYY × rryy

Round, Yellow × Wrinkled, Green

Gametes:

RY and ry

F₁ generation:

RrYy

All F₁ plants have round, yellow seeds.

The F₁ plants were then self-pollinated:

RrYy × RrYy

The four types of gametes produced by each F₁ plant are:

RY, Ry, rY and ry

The F₂ generation produces the following phenotypic ratio:

9 Round Yellow : 3 Round Green : 3 Wrinkled Yellow : 1 Wrinkled Green

Therefore, the dihybrid phenotypic ratio is:

9:3:3:1

This result supports Mendel’s Law of Independent Assortment, according to which alleles of different genes assort independently during gamete formation, under appropriate conditions.

Additional Questions & Answers (Class 12 Anthropology Chapter 2 Genetics Solutions)

Multiple Choice Questions (MCQ)

1. Who is known as the father of genetics?

(i) Bateson.

(ii) Charles Darwin.

(iii) Gregor Mendel.

(iv) Watson.

Ans: (iii) Gregor Mendel.

2. The term ‘Genetics’ was coined by:

(i) Crick.

(ii) Bateson.

(iii) Mendel.

(iv) Galton.

Ans: (ii) Bateson.

3. What is the unit of heredity?

(i) Allele.

(ii) Gene.

(iii) DNA.

(iv) Chromosome.

Ans: (ii) Gene.

4. The genotypic ratio of a monohybrid cross in F₂ generation is:

(i) 1:1.

(ii) 1:2:1.

(iii) 3:1.

(iv) 2:2.

Ans: (ii) 1:2:1.

5. Heterozygous condition is represented by:

(i) Tt.

(ii) None.

(iii) TT.

(iv) tt.

Ans: (i) Tt.

6. Reappearance of a recessive trait in F₂ proves:

(i) Mutation.

(ii) Segregation.

(iii) Hybrid vigor.

(iv) Blending.

Ans: (ii) Segregation.

7. What is the total number of chromosomes in human cells?

(i) 23.

(ii) 46.

(iii) 22.

(iv) 44.

Ans: (ii) 46.

8. Sex chromosomes in a female are:

(i) XO.

(ii) YY.

(iii) XX.

(iv) XY.

Ans: (iii) XX.

9. Alleles are:

(i) mRNA.

(ii) Alternative forms of a gene.

(iii) DNA fragments.

(iv) Identical genes.

Ans: (ii) Alternative forms of a gene.

10. Down’s syndrome occurs due to:

(i) Translocation.

(ii) Deletion.

(iii) Trisomy 21.

(iv) Monosomy.

Ans: (iii) Trisomy 21.

11. Chromosome number in Down’s syndrome:

(i) 47.

(ii) 44.

(iii) 46.

(iv) 45.

Ans: (i) 47.

12. Turner’s syndrome genotype is:

(i) XXY.

(ii) XO.

(iii) XY.

(iv) XX.

Ans: (ii) XO.

13. Which disorder causes female with webbed neck and sterility?

(i) Klinefelter’s syndrome.

(ii) None.

(iii) Turner’s syndrome.

(iv) Down’s syndrome.

Ans: (iii) Turner’s syndrome.

14. Male with underdeveloped testes and breast development is seen in:

(i) Edward’s syndrome.

(ii) Klinefelter’s syndrome.

(iii) Down’s syndrome.

(iv) Turner’s syndrome.

Ans: (ii) Klinefelter’s syndrome.

15. Who discovered Down’s syndrome?

(i) Mendel.

(ii) Langdon Down.

(iii) Bateson.

(iv) Turner.

Ans: (ii) Langdon Down.

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