Selina Textbook Solutions: Genetics - Some Basic Fundamentals | Biology Class 10 ICSE PDF Download

 Page 1


                     
A. MULTIPLE CHOICE TYPE: 
     (Select the most appropriate option) 
Question 1:  
Which one of the following has the smallest number of chromosomes? 
(a) Onion 
(b) Mouse 
(c) Monkey 
(d) Ascaris 
Solution 1: 
(d) Ascaris 
 
 
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 2: 
(a) 3 : 1 
 
 
B: VERY SHORT ANSWER TYPE: 
 
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: 
(a) - (iii) Study of laws of inheritance of characters 
(b) - (v) Chromosomes other than the pair of sex chromosomes 
(c) - (iv) A gene that can express when only in a similar pair 
(d) - (ii) The alternative forms of a gene 
(e) - (i) Chromosomes similar in size and shape 
 
 
Class X                    Chapter 2 - Genetics - Some Basic Fundamentals                          Biology
 _____________________________________________________________________________ 
Page 2


                     
A. MULTIPLE CHOICE TYPE: 
     (Select the most appropriate option) 
Question 1:  
Which one of the following has the smallest number of chromosomes? 
(a) Onion 
(b) Mouse 
(c) Monkey 
(d) Ascaris 
Solution 1: 
(d) Ascaris 
 
 
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 2: 
(a) 3 : 1 
 
 
B: VERY SHORT ANSWER TYPE: 
 
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: 
(a) - (iii) Study of laws of inheritance of characters 
(b) - (v) Chromosomes other than the pair of sex chromosomes 
(c) - (iv) A gene that can express when only in a similar pair 
(d) - (ii) The alternative forms of a gene 
(e) - (i) Chromosomes similar in size and shape 
 
 
Class X                    Chapter 2 - Genetics - Some Basic Fundamentals                          Biology
 _____________________________________________________________________________ 
Class X Chapter 03 – Genetics  Biology 
_____________________________________________________________________________ 
 
 
Question 2: 
Name two animals which have nineteen pairs of chromosomes. 
Solution 2: 
Lion, tiger, domestic cat (Any two) 
 
Question 3: 
Name any two genetic in humans. 
Solution 3: 
Colour-blindness, Thalassaemia, Sickle cell anaemia and Haemophilia (Any two) 
 
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 
 
C. SHORT ANSWER TYPE: 
 
Question 1: 
Differentiate between: 
(a) genotype and phenotype. 
(b) character and trait. 
(c) monohybrid and dihybrid cross (phenotypic ratio) 
 
Solution 1: 
Phenotype Genotype 
The observable  
Characteristic which is 
genetically controlled is called 
phenotype. 
The set of genes present in the cells of an 
organism is called its genotype. 
Character Trait 
Any heritable feature is called a 
character. 
The alternative form of a character is called 
trait. 
Monohybrid cross Dihybrid cross 
It is a cross between two pure 
breeding parent organisms with 
different varieties taking into 
consideration the alternative 
trait of only one character. 
It is a cross between two pure breeding 
parent organisms with different varieties 
taking into consideration the alternative 
trait of two characters. 
 
Page 3


                     
A. MULTIPLE CHOICE TYPE: 
     (Select the most appropriate option) 
Question 1:  
Which one of the following has the smallest number of chromosomes? 
(a) Onion 
(b) Mouse 
(c) Monkey 
(d) Ascaris 
Solution 1: 
(d) Ascaris 
 
 
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 2: 
(a) 3 : 1 
 
 
B: VERY SHORT ANSWER TYPE: 
 
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: 
(a) - (iii) Study of laws of inheritance of characters 
(b) - (v) Chromosomes other than the pair of sex chromosomes 
(c) - (iv) A gene that can express when only in a similar pair 
(d) - (ii) The alternative forms of a gene 
(e) - (i) Chromosomes similar in size and shape 
 
 
Class X                    Chapter 2 - Genetics - Some Basic Fundamentals                          Biology
 _____________________________________________________________________________ 
Class X Chapter 03 – Genetics  Biology 
_____________________________________________________________________________ 
 
 
Question 2: 
Name two animals which have nineteen pairs of chromosomes. 
Solution 2: 
Lion, tiger, domestic cat (Any two) 
 
Question 3: 
Name any two genetic in humans. 
Solution 3: 
Colour-blindness, Thalassaemia, Sickle cell anaemia and Haemophilia (Any two) 
 
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 
 
C. SHORT ANSWER TYPE: 
 
Question 1: 
Differentiate between: 
(a) genotype and phenotype. 
(b) character and trait. 
(c) monohybrid and dihybrid cross (phenotypic ratio) 
 
Solution 1: 
Phenotype Genotype 
The observable  
Characteristic which is 
genetically controlled is called 
phenotype. 
The set of genes present in the cells of an 
organism is called its genotype. 
Character Trait 
Any heritable feature is called a 
character. 
The alternative form of a character is called 
trait. 
Monohybrid cross Dihybrid cross 
It is a cross between two pure 
breeding parent organisms with 
different varieties taking into 
consideration the alternative 
trait of only one character. 
It is a cross between two pure breeding 
parent organisms with different varieties 
taking into consideration the alternative 
trait of two characters. 
 
Class X Chapter 03 – Genetics  Biology 
_____________________________________________________________________________ 
 
 
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 you account for such differences? 
Solution 2: 
The characteristics of a species such as physical appearance, body functions and behavior are 
not only the outcome of chromosome number, but these depend on the genotype of every 
organism. That means the set of genes present in the organisms may vary and therefore lion, 
tiger and domestic cat have the same number of 38 chromosomes, their characteristics (like 
different appearances) are the result of the genes located on the chromosomes. 
 
 
Question 3: 
List any three features of garden pea with their dominant and recessive traits. 
Solution 3: 
Character Dominant trait Recessive trait 
Flower Colour Purple White 
Seed Colour Yellow Green 
Seed Shape Round Wrinkled 
Pod Shape Inflated Constricted 
Flower Position Axial Terminal 
 
 
Question 4: 
Explain why generally only the male child suffers from colour blindness and not the female? 
Solution 4: 
Colour-blindness is caused due to recessive genes which occur on the X chromosome. 
 
Males have only one X chromosome. If there is recessive gene present on X chromosome, then 
the male will suffer from colour-blindness.  
 
Females have two X chromosomes. It is highly impossible that both the X chromosomes carry 
abnormal gene. Hence, if one gene is abnormal and since it is recessive, its expression will be 
masked by the normal gene present on the other X chromosome. Females are unlikely to suffer 
from colour-blindness. 
 
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) 
Page 4


                     
A. MULTIPLE CHOICE TYPE: 
     (Select the most appropriate option) 
Question 1:  
Which one of the following has the smallest number of chromosomes? 
(a) Onion 
(b) Mouse 
(c) Monkey 
(d) Ascaris 
Solution 1: 
(d) Ascaris 
 
 
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 2: 
(a) 3 : 1 
 
 
B: VERY SHORT ANSWER TYPE: 
 
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: 
(a) - (iii) Study of laws of inheritance of characters 
(b) - (v) Chromosomes other than the pair of sex chromosomes 
(c) - (iv) A gene that can express when only in a similar pair 
(d) - (ii) The alternative forms of a gene 
(e) - (i) Chromosomes similar in size and shape 
 
 
Class X                    Chapter 2 - Genetics - Some Basic Fundamentals                          Biology
 _____________________________________________________________________________ 
Class X Chapter 03 – Genetics  Biology 
_____________________________________________________________________________ 
 
 
Question 2: 
Name two animals which have nineteen pairs of chromosomes. 
Solution 2: 
Lion, tiger, domestic cat (Any two) 
 
Question 3: 
Name any two genetic in humans. 
Solution 3: 
Colour-blindness, Thalassaemia, Sickle cell anaemia and Haemophilia (Any two) 
 
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 
 
C. SHORT ANSWER TYPE: 
 
Question 1: 
Differentiate between: 
(a) genotype and phenotype. 
(b) character and trait. 
(c) monohybrid and dihybrid cross (phenotypic ratio) 
 
Solution 1: 
Phenotype Genotype 
The observable  
Characteristic which is 
genetically controlled is called 
phenotype. 
The set of genes present in the cells of an 
organism is called its genotype. 
Character Trait 
Any heritable feature is called a 
character. 
The alternative form of a character is called 
trait. 
Monohybrid cross Dihybrid cross 
It is a cross between two pure 
breeding parent organisms with 
different varieties taking into 
consideration the alternative 
trait of only one character. 
It is a cross between two pure breeding 
parent organisms with different varieties 
taking into consideration the alternative 
trait of two characters. 
 
Class X Chapter 03 – Genetics  Biology 
_____________________________________________________________________________ 
 
 
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 you account for such differences? 
Solution 2: 
The characteristics of a species such as physical appearance, body functions and behavior are 
not only the outcome of chromosome number, but these depend on the genotype of every 
organism. That means the set of genes present in the organisms may vary and therefore lion, 
tiger and domestic cat have the same number of 38 chromosomes, their characteristics (like 
different appearances) are the result of the genes located on the chromosomes. 
 
 
Question 3: 
List any three features of garden pea with their dominant and recessive traits. 
Solution 3: 
Character Dominant trait Recessive trait 
Flower Colour Purple White 
Seed Colour Yellow Green 
Seed Shape Round Wrinkled 
Pod Shape Inflated Constricted 
Flower Position Axial Terminal 
 
 
Question 4: 
Explain why generally only the male child suffers from colour blindness and not the female? 
Solution 4: 
Colour-blindness is caused due to recessive genes which occur on the X chromosome. 
 
Males have only one X chromosome. If there is recessive gene present on X chromosome, then 
the male will suffer from colour-blindness.  
 
Females have two X chromosomes. It is highly impossible that both the X chromosomes carry 
abnormal gene. Hence, if one gene is abnormal and since it is recessive, its expression will be 
masked by the normal gene present on the other X chromosome. Females are unlikely to suffer 
from colour-blindness. 
 
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) 
Class X Chapter 03 – Genetics  Biology 
_____________________________________________________________________________ 
 
Genotypic Ratio - 1(Homozygous Black Fur):2 (Heterozygous Black Fur): 1 (Homozygous 
Brown Fur) 
 
D: LONG ANSWER TYPE: 
 
Question 1: 
Explain the following terms: 
(a) heterozygous  
(b) Homozygous 
(c) pedigree chart. 
Solution 1: 
(a) Heterozygous:  The condition in which a pair of homologous chromosomes carries 
dissimilar alleles for a particular character. 
For example - 
(i) A daughter (XX
o
) from a normal homozygous mother for colour vision (XX)  and  
     a colour blind father has one normal and one defective allele (X
o
Y). 
(ii) Certain tongue rollers are heterozygous with Rr genotype. 
(b) Homozygous:  The condition in which a pair of homologous chromosomes carries similar 
alleles for a particular character. 
For example - 
(i) A colorblind daughter (X
o
X
o
) will have both the X chromosomes with defective 
alleles. 
(ii) A non-roller will have rr (homozygous) genotype. 
(c) Pedigree Chart:  A pedigree chart is a diagram that shows the occurrence and appearance 
or phenotypes of a particular gene or organism and its ancestors from one generation to the 
next. In the pedigree chart, males are shown by squares and females by circles. 
 
 
Question 2: 
State the three mendel’s laws of inheritance. 
 
Solution 2: 
Mendel's laws of inheritance are:  
(i)  Law of Dominance: Out of a pair of contrasting characters present together, only     one is 
able to express itself while the other remains suppressed. The one that expresses is the dominant 
character and the one that is unexpressed is the recessive one. 
(ii)  Law of Segregation : The two members of a pair of factors separate during the formation 
of gametes. The gametes combine together by random fusion at the time of zygote formation. 
This law is also known as 'law of purity of gametes'. 
(iii)  Law of Independent Assortment: When there are two pairs of contrasting characters, the 
distribution of the members of one pair into the gametes is independent of the distribution of the 
other pair. 
 
 
Page 5


                     
A. MULTIPLE CHOICE TYPE: 
     (Select the most appropriate option) 
Question 1:  
Which one of the following has the smallest number of chromosomes? 
(a) Onion 
(b) Mouse 
(c) Monkey 
(d) Ascaris 
Solution 1: 
(d) Ascaris 
 
 
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 2: 
(a) 3 : 1 
 
 
B: VERY SHORT ANSWER TYPE: 
 
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: 
(a) - (iii) Study of laws of inheritance of characters 
(b) - (v) Chromosomes other than the pair of sex chromosomes 
(c) - (iv) A gene that can express when only in a similar pair 
(d) - (ii) The alternative forms of a gene 
(e) - (i) Chromosomes similar in size and shape 
 
 
Class X                    Chapter 2 - Genetics - Some Basic Fundamentals                          Biology
 _____________________________________________________________________________ 
Class X Chapter 03 – Genetics  Biology 
_____________________________________________________________________________ 
 
 
Question 2: 
Name two animals which have nineteen pairs of chromosomes. 
Solution 2: 
Lion, tiger, domestic cat (Any two) 
 
Question 3: 
Name any two genetic in humans. 
Solution 3: 
Colour-blindness, Thalassaemia, Sickle cell anaemia and Haemophilia (Any two) 
 
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 
 
C. SHORT ANSWER TYPE: 
 
Question 1: 
Differentiate between: 
(a) genotype and phenotype. 
(b) character and trait. 
(c) monohybrid and dihybrid cross (phenotypic ratio) 
 
Solution 1: 
Phenotype Genotype 
The observable  
Characteristic which is 
genetically controlled is called 
phenotype. 
The set of genes present in the cells of an 
organism is called its genotype. 
Character Trait 
Any heritable feature is called a 
character. 
The alternative form of a character is called 
trait. 
Monohybrid cross Dihybrid cross 
It is a cross between two pure 
breeding parent organisms with 
different varieties taking into 
consideration the alternative 
trait of only one character. 
It is a cross between two pure breeding 
parent organisms with different varieties 
taking into consideration the alternative 
trait of two characters. 
 
Class X Chapter 03 – Genetics  Biology 
_____________________________________________________________________________ 
 
 
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 you account for such differences? 
Solution 2: 
The characteristics of a species such as physical appearance, body functions and behavior are 
not only the outcome of chromosome number, but these depend on the genotype of every 
organism. That means the set of genes present in the organisms may vary and therefore lion, 
tiger and domestic cat have the same number of 38 chromosomes, their characteristics (like 
different appearances) are the result of the genes located on the chromosomes. 
 
 
Question 3: 
List any three features of garden pea with their dominant and recessive traits. 
Solution 3: 
Character Dominant trait Recessive trait 
Flower Colour Purple White 
Seed Colour Yellow Green 
Seed Shape Round Wrinkled 
Pod Shape Inflated Constricted 
Flower Position Axial Terminal 
 
 
Question 4: 
Explain why generally only the male child suffers from colour blindness and not the female? 
Solution 4: 
Colour-blindness is caused due to recessive genes which occur on the X chromosome. 
 
Males have only one X chromosome. If there is recessive gene present on X chromosome, then 
the male will suffer from colour-blindness.  
 
Females have two X chromosomes. It is highly impossible that both the X chromosomes carry 
abnormal gene. Hence, if one gene is abnormal and since it is recessive, its expression will be 
masked by the normal gene present on the other X chromosome. Females are unlikely to suffer 
from colour-blindness. 
 
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) 
Class X Chapter 03 – Genetics  Biology 
_____________________________________________________________________________ 
 
Genotypic Ratio - 1(Homozygous Black Fur):2 (Heterozygous Black Fur): 1 (Homozygous 
Brown Fur) 
 
D: LONG ANSWER TYPE: 
 
Question 1: 
Explain the following terms: 
(a) heterozygous  
(b) Homozygous 
(c) pedigree chart. 
Solution 1: 
(a) Heterozygous:  The condition in which a pair of homologous chromosomes carries 
dissimilar alleles for a particular character. 
For example - 
(i) A daughter (XX
o
) from a normal homozygous mother for colour vision (XX)  and  
     a colour blind father has one normal and one defective allele (X
o
Y). 
(ii) Certain tongue rollers are heterozygous with Rr genotype. 
(b) Homozygous:  The condition in which a pair of homologous chromosomes carries similar 
alleles for a particular character. 
For example - 
(i) A colorblind daughter (X
o
X
o
) will have both the X chromosomes with defective 
alleles. 
(ii) A non-roller will have rr (homozygous) genotype. 
(c) Pedigree Chart:  A pedigree chart is a diagram that shows the occurrence and appearance 
or phenotypes of a particular gene or organism and its ancestors from one generation to the 
next. In the pedigree chart, males are shown by squares and females by circles. 
 
 
Question 2: 
State the three mendel’s laws of inheritance. 
 
Solution 2: 
Mendel's laws of inheritance are:  
(i)  Law of Dominance: Out of a pair of contrasting characters present together, only     one is 
able to express itself while the other remains suppressed. The one that expresses is the dominant 
character and the one that is unexpressed is the recessive one. 
(ii)  Law of Segregation : The two members of a pair of factors separate during the formation 
of gametes. The gametes combine together by random fusion at the time of zygote formation. 
This law is also known as 'law of purity of gametes'. 
(iii)  Law of Independent Assortment: When there are two pairs of contrasting characters, the 
distribution of the members of one pair into the gametes is independent of the distribution of the 
other pair. 
 
 
Class X Chapter 03 – Genetics  Biology 
_____________________________________________________________________________ 
 
Question 3: 
Does the sex of the child depend on the father or it is just a matter of chance? Discuss 
Solution 3: 
The sex of the child depends on the father. The egg contains only one X chromosome, but half 
of the sperms contain X-chromosome whereas the other half contains Y-chromosome. It is 
simply a matter of chance as to which category of sperm fuses with the ovum and this 
determines whether the child will be male or female. 
 
If the egg fuses with X-bearing sperm, the resulting combination is XX and the resulting child 
is female.  
If the egg fuses with Y-bearing sperm, the resulting combination is XY and the resulting child 
is male. 
 
 
E. STRUCTURED / APPLICATION AND 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: 
 
 
 B B 
B BB Bb 
B Bb bb 
 
Genotype - 1(Homozygous Black Fur) :2 (Heterozygous Black Fur):1 (Homozygous Brown 
Fur) 
Phenotype - 3 (Black Fur) :1(Brown Fur)