Selina Concise Class 10 Biology Solution Chapter No. 2- ‘Structure of Chromosomes, Cell Cycle and Cell Division’ For ICSE Board Students.
A)
1) Chromatin material is formed of
a) DNA only
b) DNA and Histones
c) Histone only
d) Nucleotide
Answer:- b) DNA and Histones
Explanation: DNA fiber and Histone protein are involved in the formation of Chromatin material.
2) The term “chromosomes ”literally means.
a) Inherited body
b) Twisted threads
c) Colored bodies
d) shining threads
Answer :-c) Colored bodies
Chromo = Colors
Soma = body
Thus the meaning of chromosomes is colored bodies.
3) The number of Chromosomes in a certain type of cell division is halved. This kind of cell division occur in
a) only testis
b) only ovary
c) Both ovary and testis
d) all body cell
Answer:-c) both ovary and testis
Explanation: Ovary Contains eggs with half number of Chromosomes and testis contains the sperms which have half number of chromosomes. Only X or Only Y (Sex chromosome)
4) In which one of the following option the two stage of mitosis have been given in correct sequence ?
a) prophase, metaphase, telophase, anaphase
b) prophase, metaphase, anaphase, telophase
c) Anaphase ,telophase, prophase, metaphase
d) Telophase, anaphase, prophase, metaphase
Answer:-
b) Prophase, metaphase, anaphase, telophase
These is the correct sequence of the Mitosis cell division.
5) Synthesis phase in the cell cycle is called so for the synthesis of more of
a) RNA
b) RNA and proteins
c) DNA
d) Glucose
Answer:-c) DNA
Explanation: DNA is the carrier of hereditary characters which is transfers the hereditary information. The formation of DNA takes place in synthesis phase of cell cycle.
B)
1) Name the following :-
The repeatingcomponents of each DNA strand lengthwise.
Answer:-
Nucleotides are the respecting components of each DNA strand lengthwise.
B.) complex structure consisting of DNA strand and a core of histones.
Answer:-The complex structure of DNA strand and the core of histone is nucleosome.
C.) type of bond which joins the complementary nitrogenous bases.
Answer:-
Hydrogen bonds are the bond which joins the complementary nitrogenous bases.
D.) three components of a nucleotide.
Answer:-
The three components of nucleotide are Phosphate, sugar and nitrogenous bases.
2) Solution:
Cell A- which is gone through mitotic cell division will produce the 2 cells.
Cell B – which is gone through meiotic cell division will produce the 4 cells.
3) Solution:
Answer:-
Column A | Answer |
A) Chromosomes get arranged in a horizontal plane at the equator | Metaphase |
B) Daughter Chromosomes move to the opposite poles of a spindle. | Telophase |
C) Chromosomes become visible as fine as fine long threads | Prophase |
D) Chromosomes lose Their distinctiveness And gradually become Transformed into a Chromatin network | Anaphase |
4) Fill in the blanks Solution:
a)
Answer:- DNA replicates in the synthesis phase of the cell cycle.
b)
Answer:-
Mitosis occurs in our Somatic (body) cell.
c)
Meiosis occurs only in reproductive cells.
d)
Answer:-
Modern humans have 46 Chromosomes. Their sperms and egg will have 23 chromosomes each.
e)
Answer:-
During the pairing of Chromosomes in meiosis, the homologous Chromosomes come to lie side by side.
f)
Answer:-
The two non-sister chromatids of a paired Chromosomes are attached to each other at Chiasma during the process of crossing over.
C)
1) Solution:
Answer:-
Chromatin fiber :→
Chromatic fiber is the DNA molecule present in the Chromosomes Which is associated with the histone protein.
Chromosomes :→
Chromosomes are present in the Nucleus of the cell, which are organized by the discrete units of the DNA.
2) Solution:
Answer:-
The components by which the rungs of the DNA ladder is made up of are adenine, Guanine, Cytosine and Thymine.
3) Solution:
(a)
Answer:-
The four nitrogenous bases in the DNA are Adenine, Guanine, Thiamine and Cytosine.
(b)
Answer:-
Genes are specific sequence of nucleotide on a chromosome.
(c)
Answer:-
A nucleotide is composed of a Phosphate, a sugar (pentose) and a nitrogenous base.
(d)
Answer:-
Nucleosome are group of histone molecules surrounded by DNA strands.
(e)
Answer:-
If there are 46 chromosomes in a cell, there will be 46 chromatin fibers inside the nucleus during interphase.
D)
(1) Solution:
(a)
Answer:-False
Our surface skin cells are continuously get dried and dead. Hence these are removed from the skin and at that place new underlying skin cells are replaced.
(b)
Answer:-False.
Nuclear membrane does not Disappears in Telophase it reappears in Telophase and disappears in Prophase.
(c)
Answer:-True.
In unicellular animals mitotic cell division can be mode of reproduction.
(d)
Answer:-True.
The crossing over occurs between Two homologous Chromosomes and there is exchange of chromatin fiber.
2) Solution:
a) Chromosome
Answer:-Chromosomes are the discrete units which are organized by the DNA of the cell present in Nucleus.
b) Gene
Answer:-genes are the certain specific sequence of the nucleotide present on the Chromosomes, which are encoded by the proteins. Genes contains DNA molecule. These is the hereditary unit of Life.
c) Cell division
Answer:-
The capacity of cell to divide into two or more cell is known as cell division.
Eg. Mitosis and meiosis
d) chromatid
Answer:-
Chromatids are the duplicate copies of single chromosome.
e) Aster
Answer:-
Asters are the daughter Centrioles which moves apart and goes to the opposite poles of the cell. The rays which are surrounded to the Centriole are known as asters.
(3) Solution:
(a)
Answer:-
During the sexual reproduction male gamete and female gamete fuses with each other to form the normal double number of Chromosome needed. Hence it is important that gametes must be produced by meiosis for sexual reproduction.
(b)
Answer:-
The meiosis is known as reduction division Because meiosis reduces the chromosomes number into halved. As humans have 46 Chromosomes in each cell. But in reproductive cells i.e. sex cells does not have 46 it has 23 chromosomes.
(c)
Answer:-
When there is process of reproduction takes place the mixing of genes occurs of both the parents. These mixing and recasting of genes Which produces the innumerable variations to form new daughter cell. Thus how children of the same parents are always different in some aspects.
4) Solution:
(a)
Answer:-
Cytokinesis :-
Cytokinesis is the division of cytoplasm. It occurred after the Telophase, the cytoplasm divides into two cells.
Karyokinesis:-
Karyokinesis is the division of Nucleus. Which occurs in four main phases, Prophase, metaphase, Anaphase, and Telophase. Karyokinesis occurs after the cytokinesis.
(b)
Answer:-
DNA :-
DNA is the deoxyribonucleic acid. These is made up of repeating units of nucleotides.
RNA :-
RNA is Ribonucleic acid.
(c)
Answer:-
Nucleosome :-
Nucleosomes are the structural units of the DNA which are made up of histone protein. These helps the DNA in coiling and packaging.
Nucleotide :-
Nucleotide are formed by the three components, Phosphate, sugar and Nitrogenous base. These repeating Nucleotide combines to form the strands of DNA.
(d)
Answer:-
Centrosome :-
Centrosome are present only in animal cells. It is a region surrounded to the Centrioles, near the nucleus.
Centromere :-
Centromere is the point of attachment of two chromatids.
(e)
Answer:-
Haploid :-
When there is Only single number of chromosome Is remained after the division of cell it is known as Haploid set (n).
Diploid :-
When there is double number of chromosomes present then these is known as Diploid set (2n).
(5) Solution:
Answer:-
Prophase :-
- In the Prophase the Centrioles start moving in opposite directions.
- Chromatids are formed which are duplicates of the Chromosomes.
- These sister chromatids attaches to each other at a centromere.
- Centrioles form the Aromatic spindle fibers.
- Finally the nucleolus and nuclear membrane disappears.
Anaphase:-
- The attaching point of the two chromatids get separate.
- These separated sister chromatids gets pulled at the opposite poles and spindle fibers get shorter.
- In the Animal cell, a furrow starts to appear in the middle of the cell membrane.
(6) Solution:
Answer:-
Cell cycle is divided into two phases
Which are –
1) Interphase
In these phase 2 daughter cells formed from the parents cell. It contains fully grown nucleus and slightly small cytoplasm.
It further has 3 phases :-
- G1 phase –in these phase RNA and proteins are synthesized.
- S phase – Chromosomes duplicate to form more number of DNA molecule.
- G2 phase – RNA and proteins continue to be synthesized for the growth of cell.
2) Mitosis (M-Phase)
The type of cell division in which parent cell produces 2 daughter cells.
These also contains two phases –
- Karyokinesis
- Cytokinesis
- Karyokinesis:-
It is the division of Nucleus of the cell. These contains 4 phases such as –
A.) Prophase
B.) Metaphase
C.) Anaphase
D.) Telophase
- Cytokinesis :-
It is the division of cytoplasm of the cell. It starts after completing the Telophase. These finally splits the single cell into two daughter cell.
E)
1) Given below is a schematic diagram of a portion of DNA.
(a) How many strands are shown in the diagram ?
Answer:-
2 strands are shown in the given diagram.
(b) How many nucleotide have been shown in each strand?
Answer:-
In these figure 2 nucleotides are shown in each strand.
(c) Name the parts numbered 1, 2,3, 4 and 5 respectively.
Answer:-
The names of the parts –
- Phosphate
- Sugar
- Bases
- Hydrogen bond
- Base
(d) Name the DNA unit constituted by the parts 1,2 and 3 collectively.
Answer:-
Names of the DNA constituted by the parts 1 , 2 And 3 are collectively known as Nucleotide.
(2)
Answer:
(3)
a) Answer:-
1- Centromere
2- Spindle fibers
3- Chromatids
b) Answer:-
The observation of the figure it is concluded that the figure represents the late Anaphase. These process belongs to the mitosis division occurs in animal cell. These is identified because the two sister chromatids of each of the chromosomes are separated and pulledapart from each other to the opposite polesby the spindle fibre.
c) Answer:-
The type of cell in our body where the mitotic division occurs is all over in the body cells. But the reproductive cells i.e egg cell in female and sperm cells in male does not occur the Mitosis division.
d) Answer:-
The stage comes before Anaphase is metaphase.
The diagram of Metaphase is shown below.
(4)
(5)
Answer:-
The diagram represents the phenomenon of crossing over in the meiosis. Crossing- over is the process in which the chromatids are exchanged between two homologous Chromosomes. In these process the number of chromosomes is get into halved. When the chromosomes are passed from parents n and n then there is mixing of these two gametes so that it restores the diploid number On the fertilization of the daughter. These process provides the mixing of genes.
(6)
a.)
Answer:-
The figure shows the Prophase of cell. Because it is clearly seen in the figure that Nuclear membrane of the nucleolus is disappeared.
b.)
Answer:-
The cell organelle which forms the aster is Centrioles.
c.) Name the parts labelled 1, 2 and 3.
Answer:- the labelled parts are named as –
i.) Centromere
ii.) Chromatids
iii.) Spindle fibre
d.)
Answer:-
The figure shows the Metaphase of the cell. The metaphase is confirmed due to figure shows the chromosome has Centrioles at the equator, the chromosomal spindle fibers are equally distributed to the opposite poles, these forms the metaphasic plate in the cell.
e.)
i) The number of daughter cells produced.
Answer:-
Mitosis:-
Mitosis type of cell division produces two daughter cells.
Meiosis :-
It produces 4 daughter cells.
ii) The Chromosomes number in the daughter cells.
Answer:-
Mitosis :-
a.) Mitosis is the Type Of cell division in which the Chromosomes does not get divided into halved number.
b.) It passes complete diploid set of chromosomes into its daughter cells.
c.) 2n → 2n + 2n
Meiosis :-
1) Meiosis is the type of cell division in which the chromosomes are divided into half.
2) In which it passes the half number of chromosomes in the daughter cells.
3) 2n→ n + n + n + n
(7)
(a)
Answer:-
The phase that the cell undergoing in the figure is Metaphase.
(b)
Answer:- the diploid number of chromosome shown in the figure is 4.
(c)
Answer:-
The Given cells are –
Animal cell – because it has Centrioles.
Animal cell – it has Centrioles
Plant cell – Centrioles are absent.
(8)
(a)
Answer:-
As per the given figure, it is confirmed that the cell is of animal.
i.e. animal cell.
Because, the figure shows the Centrioles. And the cell wall is absent in it, as the outline is circular.
(b)
Answer:-
The figure shown above states that the cell is undergoing mitosis.
(c)
Answer:-
The correct sequence of these four stages among themselves is –
B, C , D , A
(d)
Answer:-
Interphase is the stage which should be precede as the earliest of the sestages.
(e) Draw the stage named above inside the blank space provided
(9)
(a)
Answer:-
The figure given above does not have Centrioles hence it is confirmed that it is plant cell.
(b)
Answer:-
The shown stage is Prophase given in the figure.
(c)
Answer:-
The stage that follows the one shown here, is Metaphase.
The stage is identified by the chromosomes in the cell arranged themselves on the equatorial plate.
(d)
Answer:-
Meiosis | Mitosis |
Meiosis is the type of cell division in which the chromosomes are divided into half. | Mitosis is the Type Of cell division in which the Chromosomes does not get divided into halved number. |
It produces 4 daughter cells
|
It produces 2 daughter cells |
Chromosomes number get halved and Passed to each daughter cells.
|
Chromosomes set is passed as it is with diploid number to each daughter cells. |
2n → n + n + n + n | 2n → 2n + 2n |
5. Draw a duplicated Chromosomes add label it’s parts.