WBBSE Solutions For Class 10 Life Science And Environment Chapter 3 Heredity And Some Common Genetic Diseases

Chapter 3 Heredity And Some Common Genetic Diseases Summary

1. The inheritance of characters from one to the next generation by reproduction is called heredity. The scientific explanation of heredity was first given by Mendel and due to this, he is known as the ‘Father of genetics.
2. Chromosomes contain genes in a linear sequence. A sudden heritable change of chromosome is called a mutation.
3. The difference between different individuals resulting from reproduction is called variation. Example-Normal and roller tongue of humans.
4. Mendel introduced some important terms.
5. For example, ‘allele’ refers to two alternative forms of a gene. The location of an allele in a chromosome is called locus. One allele controls one character.
6. When the same allele is present twice then the organism is homozygous and when two different alleles are present, the organism is heterozygous.
7. The arrangement of alleles is called genotype and the external expression of a character is called phenotype.

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Chapter 3 Heredity And Some Common Genetic Diseases Long Answer Type Questions

Question 1. What are variations? Mention some phenotypically distinct human variations.
Answer:

Variations

During sexual reproduction and due to mutation, certain external and internal changes occur in some members of a population. These changes among the organisms are known as variations.

Examples of variations in the human population

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1. Free and attached earlobe:

In the human population, the soft lower portion of the pinna occurs in two different forms. One type of pinna has the lobe attached to the side of the face and another type has free hanging lobe. It is found that a pair of dominant alleles control the formation of the free lobe of the human pinna.

On the other hand, a mutated recessive gene pair is responsible for the formation of pinna with an attached lobe. This is an example of phenotypic variation seen in the human population, caused by a mutated gene.

2. Roller and normal tongue:

65-81% of the human population are able to roll their tongue but the rest cannot do so. The ability of tongue rolling is a genetic trait, controlled by a pair of dominant alleles.

A recessive mutated gene pair, on the other hand, makes one unable to roll the tongue. This is another example of human variation, caused by a recessive mutated gene.

 

 

Question 2. Mention the differences between-genotype and phenotype, dominant and recessive traits.
Answer:

Differences between genotype and phenotype

Differences between dominant and recessive traits

 

Chapter 3 Heredity And Some Common Genetic Diseases Short Answer Type Questions

Question  1. What is heredity?
Answer:

Heredity:

The process of transmission of characters from parents to offspring is known as heredity. Due to heredity, progeny of an organism of any species acquires features similar to its parents.

For example-a mango tree grows from a mango seed or a calf is born from a cow as a result of heredity.

Question  2. Who is known as the ‘Father of genetics’? Why is he regarded as the ‘Father of genetics’?
Answer:

‘Father of genetics’:

Father of genetics: Gregor Johann Mendel is character, is called dihybrid cross. A cross known as the ‘Father of genetics.

Reason:

Based on his seven year long (1856 to 1863) experiments, Mendel formulated the laws of heredity. That is why Mendel is regarded as the ‘Father of genetics!

Question  3. What is a monohybrid cross?
Answer:

Monohybrid cross:

A cross between two organisms carrying two opposite traits of a single character is called a monohybrid cross.

A cross between tall and dwarf pea plants or between black and white guinea pig are examples of a monohybrid cross.

Question  4. What is a dihybrid cross?
Answer:

Dihybrid cross:

A cross between two organisms carrying contrasting traits of two different pairs of character is called a dihybrid cross.

A cross between a pea plant with a yellow cotyledon and round seed and another one with a green cotyledon and wrinkled seed or a cross between a black and rough-furred guinea pig and a white and smooth-furred guinea pig are examples of a dihybrid cross.

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Question  5. What is a dominant trait? Give example.
Answer:

Dominant trait:

In a cross between two pure and opposite trait-bearing organisms, only one of’ the traits is expressed in the first filial (Fj) generation. This trait is called as the dominant trait of that organism.

Example:

If a cross is performed between pure violet and white flower-bearing pea plants, the Fj progeny will grow violet flowers only. Here violet flower colour is a dominant trait of that flower.

Question  6. What is a recessive trait? Give example.
Answer:

Recessive Trait:

In a cross between two pure and opposite trait-bearing organisms, one of the traits remains dormant in the first filial (F1) generation. This trait is treated as the recessive trait of that organism.

Example:

If a cross is performed between a pure black and a pure white guinea pig, all F offsprings appear black. The white coat colour does not appear in F1 generation. Here white coat colour is a recessive trait of that guinea pig.

Question  7. Define homozygous organism.
Answer:

Homozygous organism:

An organism, having identical alleles in the same locus of both of the homologous chromosomes, is called homozygous for that specific trait. Example-Identical alleles are seen in the case of pure tall (TT) or pure dwarf (tt) pea plants, therefore these are homozygous organisms.

Question  8. Define heterozygous organism.
Answer:

Heterozygous organism:

An organism, having contrasting alleles in the same locus of two homologous chromosomes, is called heterozygous for that specific trait. Example-Contrasting alleles are seen in the case of hybrid tall (Tt) pea plants, therefore, these are heterozygous organisms.

Question  9. What is an allele or allelomorph?
Answer:

Allele:

Each of the two alternative forms of a gene, located at the same loci of two homologous alternative chromosomes, controlling two expressions (traits) of the same character, is called an allele or allelomorph. Example-The genes ‘T’ and ‘t’ for tallness and dwarfness respectively are examples of alleles.

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Question  10. What is phenotype? Give examples.
Answer:

Phenotype:

Phenotype is the observable physical expression of an organism that results from its genetic makeup.

Examples:

Tall and dwarf features are the two phenotypes of a pea plant.

Question  11. What is genotype? Give examples.
Answer:

Genotype:

Genotype is the genetic constitution that controls the expression of all the traits of an organism.

Examples:

In pure tall and pure dwarf pea plants, ‘TT’ and ‘tt’ are the respective genotypes. In a hybrid tall pea plant, the genotype is ‘Tt’

Question  12. What is hybridisation?
Answer:

Hybridisation:

Hybridisation is the process of cross-breeding between contrasting varieties of the same species with reference to a single or more trait. The cross between a pure tall and a pure dwarf pea plant is a common example of plant hybridisation.

Question  13. What is meant by parental generation?
Answer:

Parental generation

Parental generation or P-generation indicates either only two individuals or two groups of organisms, between which the cross is done at the start of any hybridisation experiment. Mendelian monohybrid cross, pure tall (TT) and pure dwarf (tt) pea plants are regarded as a parental generation.

Question  14. Define first filial or F, generation.
Answer:

First filial:

The set of progeny resulting from a cross. between members of parental generation is called the first filial or F, generation.

In a cross between pure violet (VV) and pure white (vv) flower-bearing parental generation of pea plants, hybrid violet (Vv) flower-bearing pea. plants are produced. The hybrids belong to the first filial or F, generation.

Question  15. What is a character in an organism?
Answer:

Character in an organism:

In genetics, the term character is used to define a heritable feature. A character can have two or more variants, which are known as traits. The height of the pea plant is a character and each variant of height, such as, tall and dwarf, is a trait.

Question  16. What is a trait?
Answer:

Trait:

The trait is a genetically determined characteristic feature of an organism. Generally, each character has two contrasting traits, like the height of a pea plant has two opposite traits, tall and dwarf.

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Question  17. What is meant by a pure organism in heredity?
Answer:

Pure organism in heredity:

Any organism, which maintains identical phe- notypic and genotypic constitutions for successive generations, is called a pure organism. If not crossed with a tall (TT) variety, the dwarf (tt) pea plant remains as it is for generations.

Question  18. What is meant by a hybrid organism in heredity?
Answer:

Hybrid organism in heredity:

The progeny, produced from a cross between two parents with contrasting traits for one or more characters, is called a hybrid organism.

In a cross between a pure black (BB) and a pure white (bb) guinea pig, offspring are born as a hybrid with a black (Bb) coat.

Question  19. What are haploid and diploid sets?
Answer:

Haploid set:

It refers to the single set of chromosomes, found in reproductive cells or gametes. It is represented as n or N.
Diploid set:

It refers to the two sets of chromosomes found in somatic cells (cells constituting the body). It is represented as 2n or 2N.

Question 20. Differentiate between homozygous and heterozygous individuals.
Answer:

Differences between homozygous and heterozygous individuals are—

 

Chapter 3 Heredity And Some Common Genetic Diseases MCQs

Question 1. Mendelian heredity is seen in the case of—

1. Rolling and normal tongue
2. Free and attached earlobe
3. Brown and blue iris
4. All of these

Answer:  4. All of these

Question 2. The allele, responsible for the attached earlobe,is—

1. Dominant
2. Co-dominant
3. Recessive
4. Incompletely dominant

Answer: 3.  Recessive

Question 3. Which is the main genetic material of an organism?

1. DNA
2. RNA
3. Both DNA and RNA
4. Either DNA or RNA

Answer: 1. DNA

Question 4. Who coined the term ‘gene’?

1. Mendel
2. Johannsen
3. Bateson
4. Morgan

Answer:  2. Johannsen

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Question 5. Who is also known as the ‘Father of heredity’?

1. Morgan
2. Bateson
3. Johannsen
4. Mendel

Answer:  4. Mendel

Question 6. Transmission of parental characters to the next generation is known as-

1. Evolution
2. Heredity
3. Adaptation
4. Genome

Answer:  2. Heredity

Question 7. The sum total of genes of all organisms of a specific population is known as-

1. Gene pool
2. Genome
3. Genetic code
4. Heterozygote

Answer:  1. Gene pool

Question 8. The genes, located on the same loci of the homologous chromosomes, responsible for determining the opposite traits of the same character are called-

1. Alleles
2. Polygenes
3. Autosomes
4. Allosomes

Answer:  1. Alleles

Question 9. Who coined the term ‘genetics’?

1. Johannsen
2. Khorana
3. Bateson
4. Darwin

Answer:  3. Bateson

Question 10. Mendel belongs to which country?

1. Australia
2. England
3. Sweden
4. Austria

Answer:  4. Austria

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Question 11. What is the unit of heredity?

1. Chromosome
2. Gene
3. DNA
4. RNA

Answer: 2. Gene

Question 12. Who proposed the term ‘gene’ for Mendel’s factor?

1. Mendel
2. Johannsen
3. Bateson
4. Morgan

Answer:  2. Johannsen

Question 13. Permanent heritable change of gene is called-

1. Allele
2. Mutation
3. Evolution
4. Adaptation

Answer: 2. Mutation

Question 14. Who introduced the concept of mutation?

1. Mendel
2. Darwin
3. Morgan
4. De Vries

Answer:  4. De Vries

Question 15. Roller tongue is a type of character.

1. Recessive
2. Dominant
3. Incompletely dominant
4. None of the above

Answer:  2. Dominant

Question 16. The external expression of a character is called-

1. Genotype
2. Phenotype
3. Allele
4. Gene

Answer: 2. Phenotype

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Question 17. Aa x aa is an example of-

1. Monohybrid cross
2. Dihybrid Cross
3. Test Cross
4. None of the above

Answer: 3. Test Cross

 

Chapter 3 Heredity And Some Common Genetic Diseases Answer In A Single Word Or Sentence

Question 1. What is genetics?
Answer:

Genetics

The branch of biological science that deals with the gene and heredity, is known as genetics.

Question 2. What is the structural and functional unit of heredity?
Answer: Gene is the structural and functional unit of heredity

Question 3. Where are genes located?
Answer: Genes are located on chromosomes.

Question 4. What is it called, when sexual reproduction and random mutation lead to phenotypic and genotypic differences among individuals?
Answer: When sexual reproduction and random mutation lead to phenotypic and genotypic differences among individuals, it is termed as variation

Question 5. What is Mendelism?
Answer:

Mendelism

The findings of Mendel on the inheritance of characters from parents to offspring and Mendel’s laws of heredity, which were derived from these observations, are collectively known as Mendelism.

Question 6. Which term is used in genetics to denote the observable features of any organism?
Answer: Phenotype

Question 7. What is a gene?
Answer:

Gene

A gene is a particular segment of DNA that controls the expression of a specific biological character in an organism.

Question 8. Which term denotes the transfer of parental features to the offspring?
Answer: Heredity

Question 9. Which character is expressed in the F₁ generation of Mendelian monohybrid cross?
Answer: A dominant character is expressed in the F1 generation of the Mendelian monohybrid cross.

Question 10. Which character is not expressed in the F₁ generation of the Mendelian monohybrid cross?
Answer: A recessive character is not expressed in the F₁ generation of the Mendelian monohybrid cross.

Question 11. Name the cross between two opposite traits of a single character.
Answer: The cross between two opposite traits of a single character is called a monohybrid cross.

Question 12. Name the type of offspring that inherits identical alleles of a character from parents.
Answer: An offspring that inherits two identical alleles of a specific character from parents, is called homozygous offspring.

Question 13. Name the type of offspring that inherits two dissimilar alleles of a character from parents.
Answer: An offspring that inherits two dissimilar alleles of a specific character from parents, is called heterozygous or hybrid offspring.

Question 14. Which ratio represents the genetic constitution of the progeny of a hybrid cross?
Answer: Genotypic ratio

Question 15. What is locus?
Answer:

Locus

The region of the chromosome where a gene is located is called the locus.

Question 16. Give an example of variation inherited in man over the generation.
Answer: Hair colour

 

Chapter 3 Heredity And Some Common Genetic Diseases Fill In The Blanks

 

Question 1. A zygote having two identical alleles is called_____
Answer: Homozygot’e

Question 2. A __________is formed, by the union of two gametes carrying contrasting alleles.
Answer: Heterozygote

Question 3. __________ is the unit of heredity.
Answer: Gene

Question 4. The parental character, which is not expressed in the F₁ generation of monohybrid cross, is called _______ character
Answer: Recessive

Question 5. The specific location of a gene on a chromosome is called ______of the gene.
Answer: Locus

Question 6. The free lobed ear is formed by a pair of ______ genes.
Answer: Dominant

Question 7. Mutation generates
Answer: Variation

Question 8. Generally, the number of ______ within the cells of an organism is constant.
Answer: Chromosomes

Question 9. The human genome contains about _______ different genes
Answer: 25000

Question 10. The roller tongue-producing gene is a _______ type of gene.
Answer: Autosomal dominant

Question 11. Different forms of a gene is called _______
Answer: Allele

Question 12. In heterozygous organisms character _______ is expressed.
Answer: Dominant

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Question 13. The individual in which there are two different alleles of a gene is called _______
Answer: Heterozygote

Question 14. Individual containing Bb genotype is __________ type of individual.
Answer: Heterozygous

 

Chapter 3 Heredity And Some Common Genetic Diseases State True Or False

Question 1. Mendel is the ‘Father of genetics’
Answer: True

Question 2. The branch of science, that deals with genes and heredity, is known as genetics.
Answer: True

Question 3. Two opposite variations of a gene are known as alleles.
Answer: True

Question 4. Mendel denoted the unit of heredity as ‘gene!
Answer: False

Question 5. RNA is the universal genetic material.
Answer: False

Question 6. In the Mendelian experiment, “TT’ indicates the pure tall character of the pea plant.
Answer: True

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Question 7. A sudden heritable permanent change of chromosome or gene is called variation.
Answer: False

Question 8. Tand tallele together form a homozygote.
Answer: False

Question 9. The external expression of a character is called the phenotype.
Answer: True

 

Chapter 3 Heredity And Some Common Genetic Diseases Match The Columns

1.

Answer: 1. C, 2. A, 3. A, 4. D, 5. F, 6. G

2.

Answer: 1. E, 2. A, 3. B, 4. C, 5. D, 6. G

 

Chapter 3 Heredity And Some Common Genetic Diseases Find The Odd One Out

Question 1. Attached ear lobe, Roller tongue, Black fur of guinea pig, Free ear lobe
Answer: Attached ear lobe

Question 2. Allele, Locus, Gene, Gamete
Answer: Gene

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Question 3. RrTt, Vv, BbSs, BB
Answer: BB

Question 4. Chromosome, DNA, Gene, Zygote
Answer: Zygote

Question 5. Adaptation, Variation, Mutation, Classification
Answer: Classification

Question 6. Seed colour, Seed shape, Flower colour, Type of root
Answer: Type of root

 

Chapter 3 Heredity And Some Common Genetic Diseases Fill In The Blanks By Looking At The First Pair

Question 1. Forms of gene:Allele::Location of gene: _______
Answer: Locus

Question 2. Tall plant: phenotype:: TT: _______
Answer: Genotype

Question 3.bbss: Homozygous:: BbSs: _______
Answer: Genotype

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Question 4.TT: Dominant:: tt: _______
Answer: Recessive

 

Chapter 3 Heredity And Some Common Genetic Diseases Among The Four Concepts Given Three Of Them Belong To One Find That

Question 1. Normal and roller tongue, Black and blue eye, Variation, Attached and free earlobe
Answer: Variation

Question 2. Genetics, Monohybrid cross, Dihybrid cross, Homozygous organism
Answer: Genetics

Question 3. Tall-Dwarf, Black fur, Phenotype, Purple flower
Answer: Phenotype

Question 4. Dominant, TT, WW, BBSS
Answer: Dominant

Question 5. BbSs, Tt, Heterozygous, Yellow wrinkled pea
Answer: Heterozygous