Frank Solutions for Chapter 1 Cell Division Class 10 Biology ICSE


1. Why is cell division necessary ?
Cell division is important for a variety of reasons. One reason is that cell division is important for the growth of an organism. It is also important for cells to divide so that they can remain efficient. As all the cells are produced by the division of pre-existing cells, so each organism needs new cells for growth, replacement, repair and reproduction.

2. What do you understand by cell cycle?
The cell cycle is a series of events that take place in a cell leading to its division and duplication.

3. How is interphase important? 
Interphase is a long resting phase in the cell cycle during which the cell grows, multiplication of DNA, synthesis of RNA and proteins takes place. Thus interphase is important in the cell cycle as it allows the cell to grow and develop into a mature cell before it is able to reproduce.

4. Which cell division results in formation of ova?
Meiosis results in the formation of ova.

5. Draw labeled diagram of different steps of mitosis.

6. Describe anaphase in mitosis.
In anaphase, the two chromatids separate at the centromere and begin to move in opposite direction towards either end of the spindle network called the poles. The chromosomes bend around the centromere showing a ‘V’ or ‘J’ or ‘L’ shaped structure based on the length of its arms.

7. Write down the phases of mitosis.
The different phases of mitosis are Prophase, Metaphase, Anaphase and Telophase.

8. Where does mitosis occur?
Mitosis takes place in the body cells or somatic cells of the organisms.

9. How is mitosis important?
Mitosis is important because:
  1. It helps in the growth of tissues, organs and thus the entire organism.
  2. It helps in the repair of damaged tissues and organs.
  3. It is the method by which lower organisms reproduce.
  4. It helps in the maintenance of the hereditary characters by the replication of chromosomes

10. Mention characteristic features of mitosis.
Some characteristic features of mitosis are:
  1. It takes place in somatic cells.
  2. Chromosome number is preserved.
  3. Daughter cells produced are identical to the parent cell.
  4. It results in increase in the number of cells.

11. Give important character of meiosis.
Few important characteristics of Meiosis are:
  1. Meiosis occurs in germ cells only.
  2. It results in the formation of gametes.
  3. Chromosome number of the parent cell is halved.
  4. Daughter cells differ from the parent cell.

12. With well labelled explain meiosis.
Different stages involved in meiosis:
13. Where does meiosis take place in humans?
In humans, meiosis occurs in testes producing sperms and in the ovaries resulting in ova.

14. What is the significance of meiosis?
Significance of Meiosis:
  1. Due to meiosis, chromosome number is reduced to half in gametes and chromosome number of species is maintained.
  2. Genetic variations occur due to meiosis.
  3. The zygote on fertilization gets one maternal and one paternal chromosome in each homologous pair.

15. What is the significance of crossing over?
Significance of Crossing over:
  1. As a result of crossing over, the paternal and maternal homologous chromosomes of an organism pair up and exchange certain portions of their chromatids which lead to genetic variations.
  2. It makes the genetic information in each haploid cell unique

16. Compare meiotic and mitotic telophase.
Phase Mitosis Meiosis
Telophase 1. Daughter cells produced at the end of telophase are diploid and identical to the parent cells. 1. Daughter cells produced are haploid and different from the parent cells.

2. Two daughter cells are produced at the end of telophase. 2. Four daughter cells are formed at the end of telophase

17. Is cytokinesis necessary after karyokinesis in meiosis I?
No, cytokinesis is not necessary after karyokinesis in meiosis I. It generally takes place at the end of meiosis II when the four daughter cells are formed.

18. Define the following:
(i) Karyokinesis
(ii) Cytokinesis
(iii) Chiasmata
(i) Karyokinesis – It is the nuclear division where nucleus divides into two.
(ii) Cytokinesis – It is the division of cytoplasm in which the entire cell splits separating each nuclei.
(iii) Chiasmata – is the point where two homologous non-sister chromatids exchange genetic material in chromosomal crossover during meiosis.

19. How does cytokinesis differ in a plant and animal cell?
In an animal cell, the cytoplasm between the two daughter nuclei constricts i.e. a furrow
starts forming in the plasma membrane at the middle. This deepens towards the interior of
the cell and the cytoplasm splits into two similar daughter cells.
In plant cells on the other hand, the constriction is not observed during cytokinesis.
Instead a new cell wall is laid down along the equatorial region of the spindle network beginning at the Centre. Thus, two distinct, daughter cells are cut off.

20. Give five main differences between mitosis and meiosis.
Difference between mitosis and meiosis:
Mitosis Meiosis
1. It takes place in somatic cells. 1. It takes place in germ or reproductive cells.
2. Chromosome number of parent cell is maintained. 2. Chromosome number of parent cell is reduced to half.
3. No crossing over and no chiasmata formation. 3. Crossing over and chiasmata formation occur.
4. Cytokinesis is necessary after telophase I. 4. Cytokinesis is not necessary after telophase I.
5. Two daughter cells are formed at the end. 5. Four daughter cells are formed at the end.

21. Why is reduction division important? Why is meiosis referred to as such?
Meiosis is a reductional division as in meiosis the number of chromosomes of parent cell is
reduced to half in the daughter cells. Now, this reductional division is significant because it restores the number of chromosomes in a species.

22. Is it right to say that meiosis is responsible for maintaining chromosome number of a species? 
Yes, meiosis is responsible for maintaining the chromosome number of a species as meiosis being a reductional division involves formation of daughter cells with half the number of chromosomes.

23. How many daughter cells would you expect if 4 cells undergo
(i) Mitosis
(ii) Meiosis
(iii) Amitosis
(i) If four cells undergo mitosis, eight daughter cells will be produced.
(ii) Sixteen daughter cells will be produced.
(iii) Eight daughter cells will be produced if four cells undergo amitosis.

24. Fill in the blanks:
(i) ______ takes place in body cells resulting in growth and development.
(ii) The energy for cell division is stored as ______.
(iii) Both ______ and heterotypic divisions occur in meiosis.
(iv) Meiotic division is also called ______ division.
(v) ______ is the indirect cell division.
(i) Mitosis
(ii) ATP
(iii) Homotypic
(iv) Reduction
(v) Mitosis

25. The diagram given alongside represents a stage in cell division. Study the same and answer the question that follow:
(i) Identify the stage of cell division.
(ii) Name the parts labeled A, B, C and D.
(iii) What is the unique feature observed in this stage?
(iv) Where does this type of cell division usually occur? 
(v) How many daughter of cells are formed from this type of cell division?
(vi) Is the dividing cell shown a plant or an animal cells? Give a reason to support your answer.
(i) Anaphase in a plant cell
(ii) A – Spindle fiber
B – Cell wall
(iii) The homologous daughter chromatids or chromosomes begin to move towards opposite poles.
(iv) This type of cell division occurs usually in the somatic cells.
(v) Two daughter cells are formed from this type of cell division.
(vi) The dividing cell shown is a plant cell because of the presence of cell wall and the absence of centriole.

26. The fig given alongside shows a certain stage in a cell division in a cell with four chromosomes.
(i) Name the parts of the chromosome labeled A and B.
(ii) Name the structure C. What it its function?
(iii) Name the type of division. Give a reason.
(iv) Name the stage of division 
(v) Name the stages before and after the stage shown in the diagram.
(i) A – Duplicated chromosomes
B – Centromere
(ii) The structure C is Spindle fiber. Its function is to help in the movement of chromosomes.
(iii) The type of cell division is mitosis because all chromosomes appear to be same as there is no crossing over.
(iv) Metaphase.
(v) Prophase occurs before metaphase and after metaphase anaphase takes place

27. Choose the correct answer:

(1) Which division takes most time?
(a) mitosis
(b) amitosis
(c) meiosis
(d) none of these
(c) Meiosis

(2) Somatic cells divide by
(a) mitosis
(b) meiosis
(c) both of these
(d) none of these
(a) Mitosis

(3) Cytokinesis involves
(a) Constriction in animal cell
(b) plate formation in plant cell
(c) both of these
(d) none of these
(c) Both of these

(4) In meiosis, chromosome number is reduced by
(a) 1/2
(b) 1/4
(c) 3/4
(d) 1/3
(a) 1/2

(5) Mitosis results in
(a) gamete
(b) growth and repair
(c) both (a) & (b)
(d) none of these
(b) Growth and repair

(6) Centromere is related to
(a) movement of chromosomes
(b) DNA replication
(c) all of these
(d) spindle formation
(a) Movement of chromosomes

(7) Crossing over is a feature of
(a) meiosis
(b) mitosis
(c) amitosis
(d) none of these
(a) Meiosis

(8) DNA replication takes place in
(a) mitosis
(b) amitosis
(c) meiosis
(d) both (a) and (c)
(d) Both (a) and (c)

(9) In an interphase cell chromosome are as
(a) microtubules
(b) chromatin
(c) flagella
(d) chromatid
(b) Chromatin

(10) During mitosis which of the following disintegrate
(a) nucleolus
(b) nuclear membrane
(c) both (a) and (b)
(d) none of these
(c) Both (a) and (b)

(11) Chromosomes appear at equator in
(a) anaphase
(b) metaphase
(c) prophase
(d) telophase
(b) Metaphase

(12) Chromosomes number is halved in
(a) meiosis I
(b) meiosis II
(c) mitosis
(d) amitosis
(a) Meiosis I

(13) If after karyokinesis, cytokinesis does not occur, then result would be
(a) two nuclei, two cells
(b) one nucleus, two
(c) two cells, no nuclei
(d) one cell, two nuclei
(d) One cell, two nuclei

(14) Gametes are formed by
(a) meiosis
(b) mitosis
(c) amitosis
(d) none of these
(a) Meiosis

(15) Minimum coiling in chromosome is at
(a) prophase
(b) metaphase
(c) anaphase
(d) telophase
(d) Telophase

(16) Chromosome is most coiled at (in mitosis)
(a) telophase
(b) anaphase
(c) metaphase
(d) prophase
(d) Prophase

(17) Nuclear membrane reappears in
(a) metaphase
(b) prophase
(c) telophase
(d) anaphase
(c) Telophase
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