Selina ICSE Class 10 Biology Solutions Chapter 2 Genetics – Some Basic Fundamentals

Selina ICSE Solutions

Multiple Choice Questions (MCQs)

Question 1: Which one of the following has the smallest number of chromosomes?
(a) Onion
(b) Mouse
(c) Monkey
(d) Ascaris

Solution :


Question 2: Which one of the following is the phenotypic monohybrid ratio in F2 generation?
(a) 3:1
(b) 1:2:1
(c) 2:2
(d) 1:3

Solution :


Very Short Answer Type Questions

Question 1: Match the terms in column I with their explanations in column II.

Column I (Term)Column I (Explanation)
a. genetics(i)  Chromosomes similar in size and shapes
b. Autosomes(ii) The alternative forms of a gene
c. Recessive gene(iii) Study of laws of inheritance of characters
d. Allele(iv) A gene that can express only when in a similar pair
e. Homologous chromosomes(v) Chromosomes other than the pair of sex chromosomes.

Solution 1:

Column I (Term)Column I (Explanation)
a. genetics(iii) Study of laws of inheritance of characters
b. Autosomes(v) Chromosomes other than the pair of sex chromosomes
c. Recessive gene(iv) A gene that can express when only in a similar pair
d. Allele(ii) The alternative forms of a gene
e. Homologous chromosomes(i) Chromosomes similar in size and shape

Question 2: Name two animals which have nineteen pairs of chromosomes.
Solution 2:
Two animals which have nineteen pairs of chromosomes –
1. Lion
2. Tiger

Question 3: Name any two genetic in humans.
Solution 3:

Two genetic in humans –
1. Colour-blindness,
2. Sickle cell anemia

Question 4: Which one of the following genotypes is homozygous dominant and which one homozygous recessive in regards to tongue rolling: Rr, rr, RR 
Solution 4:

Homozygous dominant – RR
Homozygous recessive – rr

Short Answer Type Questions

Questions 1: Differentiate between:
(a) Genotype and phenotype.
(b) Character and trait.
(c) monohybrid and dihybrid cross (phenotypic ratio)
Solution 1:

Phenotype refers to an observable characteristic that is genetically controlled. Nutrition, temperature, humidity, and stress are among the environmental factors that influence phenotypic.The genotype of an organism refers to the set of genes found in its cells. As a result, a gene can exist in different forms in different organisms.
A character is a heritable characteristic is a recognizable feature, which helps in the identification of the organism.Trait refers to a character’s alternate form which is a distinct variation of a phenotypic
Monohybrid crossDihybrid cross
It’s a cross of two pure breeding parent organisms of different types, with only one character’s alternative trait taken into account.It’s a hybrid between two pure breeding parent organisms of distinct types, with the alternative trait of two characters taken into account.

Question 2: Among lion, tiger and domestic cat, al the three have the same number of 38 chromosomes, yet they have different appearances. How do your account for such differences?
Solution 2:
The physical appearance, physiological functions, and behavior of a species are not only determined by chromosome number but also depend on the genotype of each individual. That means that the set of genes present in the organisms might differ, and while the lion, tiger, and domestic cat all have 38 chromosomes, their properties (such as varied appearances) are determined by the genes located on the chromosomes.

Question 3: List any three features of garden pea with their dominant and recessive traits.
Solution 3:

CharacterDominant traitRecessive trait
Flower ColourPurpleWhite
Seed ColourYellowGreen
Seed ShapeRoundWrinkled
Pod ShapeInflatedConstricted
Flower PositionAxialTerminal

Question 4: Explain why generally only the male child suffers from colour blindness and not the female?
Solution 4:
There is only one X chromosome in males. If a recessive gene on the X chromosome is present, the man will develop colour blindness.
The X chromosome is shared by both males and females. It’s exceedingly unlikely that both X chromosomes contain defective genes. As a result, if one gene is faulty, its expression will be disguised by the normal gene on the other X chromosome because it is recessive. Females are less likely to be colorblind than males.

Question 5: In a certain species of animals, black fur (B) is dominant over brown fur (b) Show the possible ratio of genotypes and phenotypes of the offspring of the pure breeding different coloured parents.
Solution 5:
Phenotypic Ratio – 3 (Black Fur):1 (Brown Fur)
Genotypic Ratio – 1(Homozygous Black Fur):2 (Heterozygous Black Fur): 1 (Homozygous Brown Fur)

Long Answer Type Question:

Question 1: Explain the following terms:
(a) heterozygous
(b) Homozygous
(c) Pedigree chart.
Solution 1:
(a) Heterozygous: When a pair of homologous chromosomes has distinct alleles for a certain character, this is called heterozygous.
For example –
(i) A girl (XXo) with one normal and one faulty allele for colour vision (XX) from a normal homozygous mother and a colour blind father has one normal and one defective allele (XoY).
(ii) The Rr genotype is heterozygous in some tongue rollers.
(b) Homozygous: When a pair of homologous chromosomes carry similar alleles for the same character, this is known as homozygosity.
For example –
(i) A colorblind daughter (XoXo) will have faulty alleles on both X chromosomes.
(ii) A non-genotype roller is rr (homozygous).
(c) Pedigree Chart: A pedigree chart is a graphic that depicts the appearance and phenotypes of a gene or organism, as well as its ancestors, from one generation to the next. Males are represented by squares in the pedigree chart, while females are represented by circles.

Question 2: State the three Mendel’s laws of inheritance.
Solution 2:
Mendel’s laws of inheritance are:
(i) Law of Dominance: Only one of two opposing characters present at the same time is able to express themselves, while the other is restrained. The dominant character is the one who expresses, whereas the recessive character is the one who does not.
(ii) Law of Segregation: During the production of gametes, the two members of a pair of components split. At the time of zygote development, the gametes fuse together at random. This law is also known as the ‘law of gamete purity.’
(iii) Law of Independent Assortment: The distribution of members of one pair into the gametes is independent of the distribution of the other pair when there are two pairs of contrasting characters.

Question 3: Does the sex of the child depend on the father or it is just a matter of chance? Discuss
Solution 3:

The father determines the child’s sex. Although the egg only has one X chromosome, half of the sperms have the X chromosome and the other half have the Y chromosome. What kind of sperm fuses with the ovum is just a question of chance, and this determines whether the child will be male or female.
If an egg is fertilized by X-bearing sperm, the resultant combination is XX, and the child is female.
When an egg is fertilized with Y-bearing sperm, the resulting combination is XY, and the child is male.

Structured / Application / Skill Type:

Question 1: In a certain species of animals, black fur (B) is dominant over brown fur (b) Predict the genotype and phenotype of the offspring when both parents are ‘Bb’ or have heterozygous black fur.
Solution 1:

Genotype – 1(Homozygous Black Fur):2 (Heterozygous Black Fur):1 (Homozygous Brown Fur)
Phenotype – 3 (Black Fur):1(Brown Fur)

Question 2: Two pairs (A & B) of rabbits were crossed as given below:

(a) Can you tell which coat colour (black or white) is dominant? ………………………..
(b) Is the coat colour sex-linked? …………………..
Solution 2:
a) Black
b) No

Question 3: Make a punnett square for finding out the proportion of different genotypes in the progeny of a genetic cross between.
(a) A pure tall (TT) pea plant with a pure dwarf (tt) pea plant.
(b) red flower variety of pea (RR) with white flower variety of pea (rr)
Solution 3:


Genotype – 1(Homozygous tall):2 (Heterozygous tall):1 (Homozygous dwarf)
Phenotype – 3 (Tall):1(Dwarf)

Genotype – 1(Homozygous red):2 (Heterozygous red):1 (Homozygous white) Phenotype – 3 (Red):1(White)

Question 4: A family consists of two parents and their five children and the pedigree chart below shows the inheritance of the trait colour blindness in them.

(a) Who is coloring blind in the parents – the Father or the Mother?
Solution 4:
(a) Father
(b) Two sons and three daughters
(c) The child 1 (daughter) is colour blind
(d) X chromosome
(e) Hemophilia

Selina ICSE Class 10 Biology Solutions Chapter 2 Genetics - Some Basic