Karnataka 1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division

1st PUC Biology Cell Cycle and Cell Division One Marks Questions and Answers

Question 1.
What is karyokinesis?
Answer:
The division of nucleus is called karyokinesis.

Question 2.
What is interphase?
Answer:
Non dividing phase of cell between the mototic divisions is interphase.

1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division

Question 3.
What is synapsis?
Answer:
The process of pairing of homologous chromosomes is called Synapsis.

Question 4.
What are Chiasmata?
Answer:
The regions where segments of non sister chromatids of the bivalents are exchanged are called chiasmata.

1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division

Question 5.
Who first described mitosis in plants?
Answer:
Flemming.

Question 6.
What are the two stages in cell cycle?
Answer:
Interphase and M phase.

Question 7.
Can there be mitosis without DNA replication in A‘S’ phase?
Answer:
No.

1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division

Question 8.
Can there be DNA replication without cell division?
Answer:
Yes.

Question 9.
What is the average cell cycle span for a mammalian cell?
Answer:
24 hours.

Question 10.
Between a prokaryote and a eukaryote, which cell has a shorter cell division time?
Answer:
Prokaryote

Question 11.
Which of the phases of cell cycle is of longer duration?
Answer:
Interphase

Question 12.
Name the stain commonly used to colour chromosomes.
Answer:
Orcein, Acetocarmine.

1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division

Question 13.
Which tissue of animals and plants exhibits meiosis?
Answer:
Animals, Gonads (Testis – spermatocytes, Ovary – oocytes)

Question 14.
At what Stages of cell cycle does DNA synthesis take place.
Answer:
S-phase of interphase.

Question 15.
Smaller, lipid soluble molecules diffuse faster through cell membrane, but the movement of hydrophilic substances is facilitated by certain transporters which are chemically
Answer:
Proteins.

1st PUC Biology Cell Cycle and Cell Division Two Marks Questions and Answers

Question 1.
Write the significance of Mitosis / Metosis.
Answer:
Significance of Mitosis:
(i) Distribution of equal number of chromosomes to the daughter cells which maintains a constant chiomosome number.
(ii) Mitosis increases the number of cells, and hence so it contributes to growth.

Significance of Meiosis:
(i) Meiosis brings genetic crossing over and random distribution of paternal and maternal chromosomes to daughter cells.
(ii) Recombination produces variations and variations are the source of organic evolution.

Question 2.
Write any 2 differences between Mitosis and Meiosis.
Answer:
(i) Mitosis consists of single nuclear divisions.
Meiosis consists of two nuclear divisions.
(ii) In Mitosis, crossing over is absent.
In Meiosis, crossing over is present.

1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division

Question 3.
Distinguish cytokinesis from karyokinesis.
Answer:
Cytokinesis is the division of cytoplasm and karyokinesis is the division of the nucleus.

Question 4.
What is the GO (quiescent phase) of cell cycle?
Answer:
It is the cells that donot need no divide fun their, exit GO, phase of the cell division phase, to enter an inactive phase called GO. They remain metabolically active but do not proliferate (i.e. multiply) phase where cell exits from cell division of it under takes growth phase.

Question 5.
Why is mitosis called equational division?
Answer:
The number of chromosomes in the parent and daughter cells are the same in mitosis. Hence it is called equational division.

1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division

Question 6.
How does cytokinesis in plant cells differ from that in animal cells?
Answer:
1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division.2

Question 7.
Find examples where the four daughter cells from meiosis are equal in size and where they are found unequal in size.
Answer:
Equal daughter cells : Sporangia in plants, spermatid formation Unequal daughter cells : Ovum and polar cells during oogenesis.

Question 8.
What is the significance of meiosis?
Answer:

  • Meiosis maintains the chromosome number constant in sexually reproducing organisms. It is essential since the chromosome number is doubled after fertilization.
  • It results in crossing over and recombination of genes. This brings in variations in the populatìcn.
  • Meiosis in reproductive organs results in the fòrmation of gametes.

Question 10.
Analyse the events during every stage of cell cycle and notice how the following two parameters change:
(i) Number of chromosomes (N) per cell.
(ii) Amount of DNA content (C) per cell.
Answer:
G1 Phase : DNA and chromosome content do not change.
S Phase : Amount of DNA is twice that of the original cell.
M phase : Chromosome number per cell remains the same after M phase. DNA content is same as the original cell.

1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division

Question 11.
Label the diagram and also determine the stage at which this structure is visible.
Answer:
1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division.4

1st PUC Biology Cell Cycle and Cell Division Three Marks Questions and Answers

Question 1.
Describe the events taking place during interphase.
Answer:
1. Interphase (L Inter -between, Br. Phasis – aspect). The period between two mitotic divisions is called interphase.
(i) G1 Phase: It is the post mitotic phase and takes place at the end of cell division. During this, active synthesis of RNA and protein takes place.
(ii) S phase: It is the synthesis phase. During this phase, duplication of DNA and centriole takes place.
(iii)G2 Phase: It is the premitotic gap phase. The synthesis of RNA and protein continues in this phase

Question 2.
Name the stage of the cell cycle at which, each one of the following events occur:
(i) Chromosomes are moved to spindle equator.
(ii) Centromere splits and chromatids separate.
(iii) Pairing between homologous chromosomes takes place.
Answer:
(i) Metaphase
(ii) Anaphase
(iii) Zygotene.

Question 3.
Distinguish anaphase of mitosis from anaphase I of meiosis.
Answer:
Anaphase of mitosis:
Anaphase is the stage during which the centromere splits and the chromatids separate. The chromosomes move apart, toward the opposite poles. These chromosomes are genetically identical.

1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division

Anaphase I of meiosis:
During anaphase I, the homologous chromosomes separate, while the chromatids remain attached at their centromeres. Hence, in anaphase I, the chromosomes of each bivalent pair separate, while the sister chromatids remain together. The cleavage of the centromere is taken place in Anaphase of Mitosis, whereas it does not occur in Anaphase I of meiosis

1st PUC Biology Biomolecules Five Marks Questions and Answers

Question 1.
Explain with a neat labelled diagram the process of meiosis.
Answer:
1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division.3
Question 2.
Describe the following:
(a) synapsis
(b) bivalent
(c) chiasmata

Question 3.
Draw a diagram to illustrate your answer.
Answer:
Meiosis (Or: meios – to reduce pr to lessen) is a division which occurs in a diploid cell (or nucleus) and gives rise to four haploid cells or nuclei. Therefore meiosis is also known as reductional division.

1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division

Meiotic division:
Melotic division takes place in two successive stages namely,
(i) Meiosis I and
(ii) Meiosis II.

1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division.3

1st PUC Biology Cell Cycle and Cell Division Text Book Questions and Answers

Cell division is an intrinsic property of a cell, Walter Flemming (1882) studied the details of somatic cell division and coined the term mitosis for it.
There are three types of cell divisions:
(1) Amitosis or direct cell division.
(2) Mitosis or indirect cell division.
(3) Meiosis or reduction division.

Cell cycle:
The sequence of events that occur between the formation of a cell and its division into daughter cells, is called a cell cycle. It consists of two stages, a non living, growing interphase or inter phase and a short dividing mitotic or M – phase.

1. Interphase (L Inter – between, Br. Phasis – aspect). The period between two mitotic divisions is called interphase.

  • G1 Phase: It is the post mitotic phase and takes place at the end of cell division. During this, active synthesis of RNA and protein takes place.
  • S phase: It is the synthesis phase. During this phase, duplication of DNA and centriole takes place.
  • G2 Phase: It is the premitotic gap phase. The synthesis of RNA and protein continues in this phase.

1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division

2. Mitotic division: Mitotic division has two processes occurring simultaneously.
They are:
(A) Karyokinesis and
(B) Cytokinesis.

A. Karyokinesis: (Gr: Karyon-nucleus; kinesis-movement): It is a continuous process and for convenience divided into four stages. They are prophase, metaphase, anaphase and telophase.

I. Prophase: (Gr: pro-first, phases-stage): It follows the interphase and characterized by the following features

  • The already duplicated chromosomes become progressively shorter and thicker due
    to condensation. The spindle fibres appear between the centrioles present at the poles.
  • The nucleolus diminishes in size and finally disappears.
  • The nuclear envelope is partly disintegrated.

II. Metaphase: (Gr. Meta-after or second: phases-Stage) It is characterized by the following features.

  • Spindle fibres are completely formed.
  • The spindle fibres that are attached to chromosomes are called chromosomal fibres.
  • The chromosomes aggregate in the center of the cell. They come to lie in the equatorial places to form an equatorial plate.

1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division.1

1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division.2

 

III. Anaphase (Gr:ana-up; phases-stage):
Anaphase is characterized by the following features.

  • The two chromatids of each chromosome separate completely, to become daughter chromosomes. The two daughter chromosomes move away from the equator towards the opposite poles.
  • During anaphasic movement of chromosomes, the centromeres lead the path and the arms trail behind. As a result, the anaphasic chromosomes appear V,L,J and I shaped.

IV. Telophase (Gr:telos-end; phases-stage):
It is characterized by the following features.

  • Here, reversal of the prophasic events occur. The daughter chromosomes move and reach the opposite poles where they become thin and thread like again. These threads overlap one another to form a fine chromatin network.
  • The spindle fibres disintegrate and disappear.
  • Reconstitution of a new nuclear envelope occurs. Nucleolus reappear.

B. Cytokinesis: (Gnkytos-hollow; kinesis-movement): The division of the cytoplasm is called cytokinesis. A furrow develops in the middle of the Cell. They deepen centripetally, till the cytoplasm is divided into two equal parts. It forms two daughter cells.

1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division

Significance of Mitosis:

  • The somatic chromosome number (2n) in all the cells of an organism is effectively
    maintained by mitosis. The duplication of chromosomes occurs during interphase and their orderly behaviour during the different stages of mitosis maintains a constant chromosome number. ;
  • The daughter cells produced as a result of mitosis are quantitatively and qualitatively identical.
  • Mitosis of somatic cells helps in growth and development of multicellular organisms.
  • It forms a means of multiplication in some of the tower organisms eg: Amoeba, Euglena etc.
  • Mitosis produces new cells for the healing of wounds and for regeneration.

3. Meiosis:
Meiosis (Gr: meios – to reduce pr to lessen) is a division which occurs in a diploid cell (or nucleus) and gives rise to four haploid cells or nuclei. Therefore meiosis is also known as reductional division.

Meiotic division:
Meiotic division takes place in two successive stages namely,
(i) Meiosis I and
(ii) Meiosis II.
1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division.3

Each of these show karyokinesis and cytokinesis. These two steps involve the following

Meiosis I Meiosis II
1. Karyokinesis I
(i) Prophase I
(ii) Metaphase I
(iii) Anaphase 1
(iv) Telophase I
2. Cytokinesis I
1. Karyokinesis II
(i) Prophase II
(ii) Metaphase II
(iii) Anaphase II
(iv) Telophase II
2. Cytokinesis II

Meiosis I:
During this process the diploid parent cell divides into two daughter cells which are haploid, hence it is a reduction division.
A. Karyokinesis I:-
(I) Prophase I: It lasts for quite a long period and is studied under five substages.
(i) Leptotene
(ii) Zygotene
(iii) Pachytene
(iv) Diplotene
(v) Diakinesis.

1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division

(i) Leptotene: (Gr: leptos slender; tene – thread) :The chromosomes are thin, long and uncoiled. Each is a double chromosome consisting of two chromatids. These chromatids are held firmly.
Each chromosome appears as a string of beads, the beads are the chromomeres.

(ii) Zygotene: (Gr: Zygon-male; tene- thread) :During this stage, pairing of homologous chromosomes (half of them maternal and half of them paternal). This pairing is called synapsis. The pairs so formed are called bivalents.

Each bivalent consists of four chromatids and is therefore called a tetrad. The two chromatids of the same chromosomes are called sister chromatids and the belonging to two different chromosomes of a homologous pair are termed as non-sister chromatids.

(iii) Pachytene: (Gr: Pachiis – thick tene – thread): Crossing over takes place by breakage and reunion of chromatid segments. After, crossing over, the two chromatids of a chromosome become dissimilar.
The points of interchange are X shaped and are called chiasmata. (sing.chiasma)

(iv) Diplotene: (Gr : diplo – double; tene – thread)

  • Repulsion between homologous chromosomes begin.
  • Each tetrad now appears in different shapes i.e, X-shaped, ‘8’ shaped or ‘O’ shaped.
  • Repulsion results in terminalization of chiasmata (sliding of chiasmata towards the ends of chromosomes.

(v) Diakinesis: (Gr : dia-cross; kinesis- movement).

  • The nucleolus breaks down and disappear.
  • Spindle fibres appear.
  • Nuclear membrane breaks down.
  • Chromosomes are released into the cytoplasm.

(i) Metaphase I: It is characterized by the completion of spindle formation. In animals cells, asters are formed around the centrioles at two poles. The paired chromosomes arrange themselves on the equator of the spindle fibres.

(ii) Anaphase I: Here, the spindle fibres contract and this makes the bivalents move towards the opposite poles of the spindle without the division of centromere. The separated chromosomes or univalents are also called dyads because each of them consists of two chromatics which remain attached with each other at the centromere.

(iii) Telophase I : Chromosomes undergo uncoiling. A nuclear envelope is formed around each group of chromosomes. The nuclei do not reappear now.

1st PUC Biology Question Bank Chapter 10 Cell Cycle and Cell Division

Meiosis II:
In this division, the two chromatids of each chromosome separate from each other and go to separate daughter cells. As a result, the number of chromosomes remains the same as produced by meiosis I therefore meiosis is also called equational division.

Significance of Meiosis:

  • Meiosis maintains the chromosome number constant in sexually reproducing organisms. It is essential since the chromosome number is doubled after fertilization.
  • It results in crossing over and recombination of genes. This brings in variations in the population.
  • Meiosis in reproductive organs results in the formation of gametes.

1st PUC Biology Question Bank with Answers