Structure of Chromosome Cell Cycle and Cell Division Descriptive Type Ans Selina solutions Concise Biology for ICSE Class 10 Ch-2. In this article you will get the solutions of Descriptive Type Questions as council latest syllabus. Visit official website CISCE for detail information about ICSE Board Class-10 Biology.
Structure of Chromosome Cell Cycle and Division Descriptive Type Ans
Selina solutions Concise Biology for ICSE Class 10 Ch-2.
| Board | ICSE |
| Subject | Biology |
| Class | 10 |
| Book | Selina Concise |
| Chapter-2 | Structure of Chromosome Cell Cycle and Cell Division |
| Topics | Solutions of Descriptive Type Questions |
| Session | 2024-25 |
Structure of Chromosome Cell Cycle and Cell Division
Descriptive Type Ans Selina solutions Concise Biology for ICSE Class 10 Ch-2
Que-1: Define the following terms:
(a) Chromosome
(b) Gene
(c) Cell division
(d) Chromatid
(e) Aster
Sol:
(a) Chromosome: Chromosomes are formed of very long, highly coiled and condensed chromatin fibres which are made of DNA (about 40%) and histones (about 60%). They are present in the nucleus of the cell. They carry the chemical instructions for the reproduction of the cell.
(b) Gene:Genes are specific sequences of nucleotides on a chromosome that encode particular proteins which express in the form of some particular feature of the body. They are the units of heredity which are transferred from parents to offsprings and are responsible for some specific characteristics of the offspring.
(c) Cell Division: Cell division is the method in which the cell divides and the duplicated chromosomes get evenly distributed into the daughter cells.
(d) Chromatid: Duplicated chromosomes consist of two identical strands, each of these is called a chromatid. Before replication, one chromosome is composed of one DNA molecule. In replication, the DNA molecule is copied, and the two molecules are known as chromatids. During the later stages of cell division these chromatids separate longitudinally to become individual chromosomes.
(e) Aster: During mitosis in an animal cell, after the centrosome splits into two along with simultaneous duplication of the centrioles contained in it, each centriole is surrounded by radiating rays and is termed aster (meaning star).
Que-2: Give reason:
(a) Gametes must be produced by meiosis for sexual reproduction.
(b) Why is meiosis referred to as ‘reductional division’?
(c) The children of the same parents, howsoever similar, are different from each other in certain aspect
Sol:
(a) Gametes must be produced by meiosis for sexual reproduction because the numbers of chromosomes are reduced to half during meiosis and then the normal diploid numbers of chromosomes are regained during the process of fertilization.
(b) Meiosis is referred to as ‘reductional division’ because the number of chromosomes are reduced to half i.e. out of the 23 pairs of chromosomes in humans, only single set of chromosomes are passed on to the sex cells. This is essential because when the male and female gametes fuse during fertilization, the normal double (diploid) number of chromosomes is reacquired. The diploid number, as a rule, is expressed as “2n” and the haploid number as “n”.
(c) The mixing up or recombination of genes during meiotic division provides for the innumerable variations and diversity in the progeny. That is how, the children of the same parents, howsoever similar, are different from each other in certain aspects.
Que-3: Distinguish between the following pairs
(a) Cytokinesis and Karyokinesis
(b) DNA and RNA
(c) Nucleosome and Nucleotide
(d) Centrosome and Centromere
(e) Haploid and Diploid
Sol:
(a) Difference between Cytokinesis and Karyokinesis
| Cytokinesis | Karyokinesis |
|---|---|
| the division of the cytoplasm. | division of the nucleus. |
| occurs after karyokinesis. | the first division. |
| results in the formation of two daughter cells. | results in the formation of two nuclei. |
(b) Difference between DNA and RNA
| DNA | RNA |
|---|---|
| DNA is Deoxyribonucleic acid. | RNA is Ribonucleic acid. |
| consists of four distinct bases: Thymine, Adenine, Cytosine and Guanine. | consists of four distinct bases: Uracil, Adenine, Cytosine and Guanine. |
| The DNA is a double-stranded molecule. | The RNA is a single-stranded molecule. |
| located in the nucleus of a cell and in the mitochondria. | found in the cytoplasm, nucleus, and in the ribosome. |
(c) Difference between Nucleosome and Nucleotide
| Nucleosome | Nucleotide |
|---|---|
| Nucleosome is the complex that is made up of DNA wrapped around histone proteins. | The chemical composition of nucleotide consists of a phosphate group, a sugar and a nitrogenous base. |
(d) Difference between Centrosome and Centromere
| Centrosome | Centromere |
|---|---|
| an organelle of the animal cell surrounding the centrioles, located near the nucleus. | a non-stainable part of chromosome at which two chromatids join. |
| contains one or two centrioles which move towards the opposite poles and forms spindle fibres during cell division. | provides attachment of spindle fibres during cell division. |
(e) Difference between Haploid and Diploid
| Haploid | Diploid |
|---|---|
| Only half the number of chromosomes (only one member from each pair) is passed on to each daughter cell. | Full Set of chromosomes is passed on to each daughter cell. |
| It is denoted by n. | It is denoted by 2n. |
| This state is found during meiotic division. | This state is found during mitotic division. |
Que-4: Write full form of the following abbreviations:
(a) DNA
(b) RNA
Sol:
(a) DNA — Deoxyribonucleic acid
(b) RNA — Ribonucleic acid
Que-5: Given below are the sets of four terms. Choose the odd one and write the category of the remaining terms:
(a) Adenine, Guanine, Adrenaline, Thymine
(b) Pentose sugar, Histones, Phosphate group, Nitrogenous bases
(c) Metaphase, Anaphase, Interphase, Telophase
(d) G1 phase, M phase, G2 phase, S phase
(e) Chromoplast, Chromosome, Chloroplast, Leucoplast
Sol:
(a) Odd one out — Adrenaline
Adenine, Guanine, Thymine — Nitrogenous bases
(b) Odd one out — Histones
Pentose sugar, Phosphate group, Nitrogenous bases — form nucleotide
(c) Odd one out — Interphase
Metaphase, Anaphase, Telophase — Phases of Mitosis
(d) Odd one out — M phase
G1 phase, G2 phase, S phase — Phases of Interphase
(e) Odd one out — Chromosome
Chromoplast, Chloroplast, Leucoplast — Plastids
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