Selina Concise Class 10 Biology Solution Chapter No. 3- ‘Genetics – Some Basic Fundamentals’ For ICSE Board Students.
PROGRESS CHECK
1.) Solution:
i) Answer:- True
ii) Answer:-
Statement: “Like begets like”These is applicable on every living organisms.
iii) Answer:- True
2.) Solution:
i) Capacity to be a good cricketer
Answer:- [__×__]
ii) Curly hair
Answer:- [__✓____]
iii) Left-handedness
Answer:- [___✓__]
iv) Red -green colour blindness.
Answer:- [__✓_]
PROGRESS CHECK
1.)
i) Answer:-
Total number of pairs of Chromosomes in each body cell in humans 23 .
ii) Answer:- Number of pairs of autosomes in humans 22.
2.) Answer:-
No. These does not means that husband does not only produces only X sperm and Produces only y sperm. Human male produces both the sperms X and Y. the fertilization of female egg (X) with the male sperm (X) or (Y) is only the possibility. The couple has four daughters and not son these is possibility of the fertilization process.
PROGRESS CHECK
1) Solution:
Answer:- gene is the basic unit of hereditary.
2) Solution:
i) Allele
Answer:- Alleles are the alternative forms of genes which occupies the same locus (position) on an homologous Chromosomes, alleles have the same characteristics but the ways are Different.
ii) Dominant gene
Answer:- The gene which expresses itself in the presence of another gene Is known as Dominant gene.
iii) Genotype
Answer:- genotype is a genetic constitutions (type of genes posses)of the organism.
iv) Phenotype
Answer:- phenotype is a characters which are expressed by the organisms.
v) Recessive gene
Answer:- the gene which does not express its characters or which is suppressed in the presence of dominant gene, is known as Recessive gene.
3) Solution:
A) Human female
Answer:-
22 pairs of autosomes
1 pair of sex Chromosome
Total 23 pairs in the human female are of homozygous Chromosome.
B) Human male
Answer:-
22 pairs of autosomes are present in human male which are homozygous Chromosomes. But 1 pair of sex Chromosome is heterozygous.
5) Solution:
Answer:-
1) Colour of eyes – brown or blue
2) Hair shape – curly or straight
3) Colour vision – Normal or colour blindness
4) Skin colour – normal or albinism
PROGRESS CHECK
1) Solution:
Answer:-
Gregor Mendal discovered for the first time the basic principles of genetics.
2) Solution:
Answer:-
Common name – Garden pea
Scientific name –pisumsativum
3) Solution:
i) Monohybrid
Answer:- cross made by taking only one feature at a time is known as Monohybrid cross. It gives the breeding results between two same characters.
ii) Dihybrid
Answer:- Cross made by taking two features together is known as Dihybrid cross. It gives the breeding results between two pairs of contrasting characters.
iii) Filial generation
Answer:- the cross made between the offsprings is known as Filial generation.
4) Solution:
Answer:-
1) Flower colour – purple or white
2) Seed colour – yellow or green
3) Pod colour – green or yellow
Exercise Questions Solution
Multiple Choice Questions
1) One of the following is the phenotypic monohybrid ratio in F2 generation?
Answer:- 3:1
F2 generation of Monohybrid shows the phenotypic ratio of 3:1 in which 3 is dominant and 1 is recessive.
2) If a pure tall plant is crossed with a pure dwarf plant, the offspring will be
Answer:- c) 3 talk and 1 dwarf
The phenotypic ratio of Monohybrid cross between the pure tall and pure dwarf shows 3:1 ratio. In which 3 are tall and 1 is pure dwarf.
4) A plant with green pods and smooth with genotype GgSs will give rise to the following gametes :
Answer :-c) Gs and gs
The crossing over between the Gg and Ss will give rise to the offspring of Gs and gs.
b) VERY SHORT ANSWER TYPE
Answer:-
Column I | Answer |
a) Genetic | Study of laws of inheritance of characters |
b) Autosomes | Chromosomes other than the Pair of sex |
c) Recessive gene | A gene that can express when only in a similar pair |
d) Allele | The alternative forms of a gene |
e) Homologous Chromosomes | Chromosomes similar in size and shape |
2) Solution:
Answer:-
The two genetically transferring diseases in humans are hemophilia and Colour blindness.
3) Solution:
Rr, rr, RR.
Answer:-
Homozygous dominant :- RR
Homozygous recessive :- rr
C.) SHORT ANSWER TYPE
1.) Differentiate between:
a) genotype and phenotype.
Answer :-
Genotype :-
Genotype is the set of genes which are present in the every cell of organisms.
Phenotype :-
Phenotype is the character which can be observed externallybut these are genetically controlled.
b) character and trait.
Answer :-
Characters:-
The Feature which can be inherited with the genes are characters.
Trait :-
The alternative form of an character is trait.
c) monohybrid and dihybrid cross (phenotypic ratio in F2 generation).
Answer:-
Monohybrid cross –
The phenotypic ratio 3:1 obtained after Crossing the only one feature of pure breeding varieties at a time, is known as Monohybrid cross.
Dihybrid cross –
The phenotypic ratio 9:3:3:1 obtained after crossing with two features of pure breeding varieties is known as dihybrid cross.
2) Solution:
Answer:-
Lion, tiger and domestic cat all have 38 chromosome number, that is they have same genotypic ratio, but the they have different phenotypic ratio hence they have changes in their physical appearance, behavior and body functions, these differences are due to the genes which are carried by the Chromosomes these genes are responsible for the difference in the appearance of these animals.
3) Solution:
Answer:-
Features | Dominant traits | Recessive traits |
Pod shape
|
Inflated | Constricted |
Flower position
|
Axillary | Terminal |
Plant Height
|
Tall | Dwarf |
4) Solution:
Answer:-
Colour blindness is the inheritance diseases which is caused due to the recessive gene on “x” Chromosomes. These colour blindness patients cannot Differentiate between some colour. But it is more common in the males because in males there is only 1 x Chromosomes hence due to the recessive gene male suffers from the colour blindness. But in females there are two x chromosomes due to which one recessive gene can be suppressed by the another dominant gene. Hence in female it is not common.
D.) DESCRIPTIVE TYPE
1)
a) pedigree chart
Answer:-
Pedigree Chart is the Diagrammatic representation which shows the inheritance of the family. In these chart makes are shown by squares and females are shown by circles.
b) variations
Answer:-
Variations is the small differences among the individuals even though it is of same species.
c) Mutation
Answer:-
The sudden changes occur in one or more genes or in number of the gene or in the structure of the Chromosomes is known as Mutation. Mutation is responsible for altering the hereditary characters in cells of organisms and it changes some characters or traits of organisms.
2) Solution:
Answer:-
The three Mendel’s law of inheritance are as follows :-
a) Law of dominance :-
Among the pair of heterozygous contrasting characters only one trait/ character is able to express itself while the other gets suppressed. The character which is expressed phenotypically is known as Dominant character. And the character which is suppressed is known as Recessive character. These is the law of dominance of Mendel’s.
b) Law of segregation/ law of purity of gametes:-
During the time of gametes formation the two characters / members of pair of factors segregate or separate from each other. These does not blend with each other but combines together at the time of zygote formation. These law is known as law of segregation.
c) Law of independent assortment:-
If there is two pairs of charactersand there is distribution of alleles of one character into the gametes. The alleles are distributed independently with the another character. (As F1 hybrid of dihybrid cross)
3) Solution:
Answer:-
It is just a matter of chance, because the sex of the child is dependent over the sperms which fertilizes the egg. Males have two types of Chromosomes in their sperms x and y . If the x type of chromosome containing sperm fertilizes the egg then it is a girl child. And if the y type of sperm fertilizes the egg then it is a boy child. Eventually it is dependent over the father but it is a matter of chance.
4) Solution:
a) Karyotype and karyokinesis
Answer:-
Karyotype :-
Karyotype is a chart on which the photographs of dividing nucleus is arranged artificially according to their shape and size.
Karyokinesis :-
Karyokinesis is the nuclear changes occurring during the cell division. It is simply division of Nucleus at the time of cell division.
b) Autosomes and sex Chromosomes
Answer:-
Autosomes :-
The chromosomes which determines the general body characters height, colour etc. Is known as Autosomes chromosome. In human being there are 22 pairs of autosomes in the humans.
Sex Chromosomes :-
Sex Chromosomes are also known as allosomes. These are the Chromosomes which determines the sex of the organism. In the human being there is 1 pair of sex Chromosome.
c) Homozygous and Heterozygous Chromosomes
Answer:-
Homozygous chromosomes :-
Homozygous Chromosomes are the similar pair of chromosomes. Which may be dominant pair (RR) or recessive pair (rr).
Heterozygous chromosomes :-
Heterozygous chromosomes are the pair of Chromosomes which are not similar. Such as one dominant and another is recessive (Rr).
E) STRUCTURED/APPLICATION AND SKILL TYPE
1) Solution:
Answer:-
B = Black fur
b = brown fur
The genotypic ratio of the offspring is
= BB : Bb : bb
= 1 : 2: 1
The phenotypic ratio of the offspring is
= B : b
= 3 : 1
2)
a) Answer:-
Black coat colour is Dominant.
3)
i)
Answer:-
F2 generation :-
Gametes | T | t |
T | TT | Tt |
t | Tt | tt |
Genotypic ratio = 1:2:1
Phenotypic ratio = 3:1 (Tall: Dwarf)
ii)
Answer:-
F2 generation –
Gametes | R | r |
R | RR | Rr |
r | Rr | rr |
Genotypic ratio = 1:2:1
Phenotypic ratio = 3:1 ( Red : white )
4)
i) Solution:
Answer:-father is colour blind among the parents.
ii) Solution:
Answer:-In the family 2 sons and 3 daughters are borne.
iii) Solution:
Answer:-the child 1 which is daughter will be Colour blind.
iv) Solution:
Answer:-the gene of these trait is located on the X chromosome.
v) Solution:
Answer:-
The Hemophiliais the another trait which follows the similar pattern of inheritance.