Samacheer Class 11 Bio Botany Cell Cycle Book Back Answers & Solutions

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1Choose The Correct Answer:25 questions

Q.1The correct sequence in cell cycle is a) S M G1 G2 b) S G1 G2 M c) G1 S G2 M d) M G1 G2 Sv

Solution

c) G1 S G2 M

Answer:

c) G1 S G2 M

Q.1Most of the neurons in the brain are in …………… stage.v

(a) G 1
(b) S
(c) G 2
(d) G 0

Solution

(d) G 0

Answer:

(d) G 0

Q.2If mitotic division is restricted in G, phase the cell cycle, then the condition is known as a) S Phase b) G 2 Phase c) M Phase d) G 0 phasev

Solution

d) G 0 phase

Answer:

d) G 0 phase

Q.2Un differentiated cells include a) Stem cells in animals b) Meristematic cells in plants c) RBC which carry out the transportation of oxygen d) Mesophyll cells which carry out photosynthesis (i) a & b (ii) c & d (iii) a & c (iv) b & cv

Solution

(i) a & b

Answer:

(i) a & b

Q.3Anaphase promoting complex APC is a protein degradation machinery necessary for proper mitosis of animal cells. If APC is defective in a human cells. Which of the following is expected to occur? a) Chromosomes will be fragmented b) Chromosomes will not condense c) Chromosomes will not regregate d) Recombination of Chromosomes will occurv

Solution

c) Chromosomes will not segregate

Answer:

c) Chromosomes will not segregate

Q.3Robert Brown discovered the nucleus in the cells of …………… roots.v

(a) Mirabilis
(b) Orchid
(c) Moringa
(d) Oryza

Solution

(b) Orchid

Answer:

(b) Orchid

Q.4In the S phase of cell cycle a) Amount of DNA doubles in each cell b) Amount of DNA remain same in each cell c) Chromosome number is increased d) Amount of DNA is reduced to half in each cellv

Solution

a) Amount of DNA doubles in each cell

Answer:

a) Amount of DNA doubles in each cell

Q.4The proteins that activate the cell to perform cell division are a) Actin and Myosin b) Kinases and Cyclin c) Histamine and Cyclin d) Tubulin and Actinv

Solution

b) Kinases & Cyclin

Answer:

b) Kinases & Cyclin

Q.5The centromere is required for a) Transcription b) Crossing over c) Cytoplasmic cleavage d) movement of chromosome towards the polev

Solution

d) movement of chromosome towards the pole

Answer:

d) movement of chromosome towards the pole

Q.5The number of chromosomes in the onion cell is …………….v

(a) 8
(b) 16
(c) 32
(d) 64

Solution

(a) 16

Answer:

(a) 16

Q.6Synapsis occurs between a) m RNA and ribosomes b) spindle fibres and centromeres c) two homologous chromosomes d) a male and a female gemalev

Solution

c) two homologous chromosomes

Answer:

c) two homologous chromosomes

Q.6Mitosis is called a) Direct cell division b) Indirect cell division c) Mitotic Meiotic cell division d) Reduction divisionv

Solution

a) Direct cell division

Answer:

a) Direct cell division

Q.7In meiosis crossing over is initiated at a) Diplotene b) Pachytene c) Leptotene d) Zygotenev

Solution

b) Pachytene

Answer:

b) Pachytene

Q.7During Anaphase (I) The daughter chromosome move to the opposite poles due to the shortening of the phragmoplast (II) due to the thickening of chromosomes (III) Shortening of microtubules (IV) Shortening of astersv

Solution

(III) Shortening of microtubules

Answer:

(III) Shortening of microtubules

Q.8Colchicine prevents the mitosis of the cells at which of the following stage a) Anaphase b) Metaphase c) Prophase d) Interphasev

Solution

a) Anaphase

Answer:

a) Anaphase

Q.8Cell cycle was discovered by …………….v

(a) Singer & Nicolson
(b) Prevost & Dumans
(c) Schleider & Schwann
(d) Boveri

Solution

(b) Prevost & Dumans

Answer:

(b) Prevost & Dumans

Q.9The pairing of homologous chromosomes on meiosis is known as a) Bivalent b) Synapsis c) Disjunction d) Synergidsv

Solution

b) Synapsis

Answer:

b) Synapsis

Q.9The cells without nucleus are a) RBC – platelets, tracheids & vessels b) RBC – sievetube, companion cells thrombocytes c) WBC – platelets, companion cells & vessels d) RBC – platelets, companion cells & neuronsv

Solution

a) RBC – platelets, tracheids & vessels

Answer:

a) RBC – platelets, tracheids & vessels

Q.10Anastral mitosis is the characteristic feature of a) Lower animals b) Higher animals c) Higher plants d) All living Organismv

Solution

c) Higher plants

Answer:

c) Higher plants

Q.10The stage between two meiotic division is called a) Cytokinesis b) Interphase I c) Inter kinesis d) Interphase IIv

Solution

c) Inter kinesis

Answer:

c) Inter kinesis

Q.11Write any three significance of mitosisv

Solution

Exact copy of the parent cell is produced by mitosis (genetically identical).
* Genetic stability – daughter cells are genetically identical to parent cells.
* Repair of tissues – damaged cells must be replaced by identical new cells by mitosis.
* Regeneration – Arms of starfish.

Answer:

Q.11Replication of DNA occurs at …………… phase.v

(a) G 0
(b) G 1
(c) S
(d) G 2

Solution

Answer:

Q.12Differentiate between Mitosis and Meiosis.v

Solution

Differences between Mitosis and Meiosis
Mitosis
Meiosis
One division
Two division
The number of chromosomes remains the same
The number of chromosomes is halved
Homologous chromosomes line up separately on the metaphase plate
Homologous chromosomes line up in pairs at the metaphase plate
Homologous chromosome do not pair up
Homologous chromosome pair up to form bivalent
Chiasmata do not form and crossing over never occurs
Chiasmata form and crossing over occurs
Daughter cells are genetically identical
Daughter cells are genetically different from the parent cells
Two daughter cells are formed
Four daughter cells are formed

Answer:

Q.14Given an account of the Go phase.v

Solution

Some cells exit G 1 and enters a quiescent stage called G 0, where the cells remain metabolically active without proliferation. Cells can exist for long periods in G 0 phase. In G 0 cells cease growth with reduced rate of RNA and protein synthesis. The G 0 phase is not permanent. Mature neuron and skeletal muscle cell remain permanently in G 0. Many cells in animals remains in G 0 unless called onto proliferate by appropriate growth factors or other extracellular signals. G 0 cells are not dormant.

Answer:

Q.15Write about the Pachytene and Diplotene stage of Prophase I.v

Solution

3. Pachytene stage
* Chromosome appear as bivalent or tetrads
* 4 chromatids & 2 centromeres are seen
* Synapsis of homologous chromosomes between non-sister chromatids completes except at chiasmata where crossing over occurs
* Recombination (exchange of chromosomal bits is completed by the end) – but chromosomes are linked at the sites of crossing over
* Enzyme – Recombinase mediates the process.
4. Diplotene
* Synaptonemal complex disassembled & dissolves
* Nonsister chromatids of homologous chromosomes get attached where x like shape occur at Crossing over known as chiasmata holding the homologous chromosomes together the homologous chromosomes tend to separate except at chiasmat
* The sub-stage last for days or years depending on the sex & the organism follows Pachytene
* synaptical complex disassembled & dissolves
* The chromosomes are actively transcribed in females as the eggs stores up materials for embryonic development
* Exception In Lamp brush chromosome prominent loops occur.
11th Bio Botany Guide Cell Cycle Additional Important Questions and Answers
I.Choose the correct answer: (1 Marks)

Answer:

2II. Find out the true and false statements from the following and on that basis find the correct answer.3 questions

Q.1(I) Nucleolus disappear during the metaphase stage of mitosis (II) The microtubules arrange to form asters in plant cells (III) In plant cells phragmoplast is formed prior to the formation of cell plate (IV) Mitosis is responsible for the Regeneration of lost arms of starfishv

Solution

b) False – False – True- True

Answer:

b) False – False – True- True

Q.2(i) The word Protoplasm was coined by – Purkinje (ii) Structure of bacteria was observed first – Edouard Van Beneden through a microscope by (iii) Centrosome & Chromosome theory – Theodor Boveri Proposed by (iv) Cell division in round Worm was – Walther Flemming Observed byv

Solution

b) True – False – True – False

Answer:

b) True – False – True – False

Q.3(i) C Value is the amount in picograms of DNA contained within a haploid Nucleus (ii) Nucleolan membrane disappear during Ana Phase stage of mitosis (iii) The arrangement of microtubules is called to form Asters -, which is a unique feature of plant cells (iv) One of the protein synthesis in G2 – phase is known as Maturation Promoting Factorv

Solution

a) True – False – False – True
III. Find out the correct match from the following.

Answer:

a) True – False – False – True
III. Find out the correct match from the following.

3III. Find out the correct match from the following.2 questions

Q.1Zygotene – Chromosomes appear as tetrads Pachytene – Synapsis of homologous chromosomes occur Diplotene – Condensation of chromosomes takes place Diakinesis – Terminalisation of chiasmata occur & Nucleolus Disappearv

Solution

Diakinesis -Terminalisation of chiasmata occur & Nucleolus Disappear

Answer:

Diakinesis -Terminalisation of chiasmata occur & Nucleolus Disappear

Q.2Duration of different Phases of cell cycle given find out the correct match (I) S Phase – 12 Hours (II) G1 Phase – 11 Hours (III) G2 Phase – 4 Hours (IV) M Phase – 2 Hoursv

Solution

(III) G2 Phase – 4 Hours
IV. Find out the Wrong match

Answer:

(III) G2 Phase – 4 Hours
IV. Find out the Wrong match

4IV. Find out the Wrong match31 questions

Q.1(I) The chromosome does not divide as chromatids, for centromere does not divide – Anaphase I (II) The chromatids move to the opposite poles by the splitting of the centromere – Anaphase (III) Sister chromatids get separated by splitting of Centromere – Anaphase II (IV) Homologous chromosomes appear as bivalent or tetrad – Metaphase IIv

Solution

(IV) Homologous chromosomes appear as bivalent or tetrad – Metaphase II

Answer:

(IV) Homologous chromosomes appear as bivalent or tetrad – Metaphase II

Q.1Match the following and find the (I) Robert Brown – A) Coined the word cell (II) Robert Hook – B) Coined the word Mitosis (III) Schleiden & Schwann – C) Studied the presence of Nucleus in cells (IV) Waither Flemming – D) Cell theoryv

Solution

d) C-A- D- B

Answer:

d) C-A- D- B

Q.1Read the following Assertion and Reason. Find the correct answer Assertion A: The mitochondrial inheritance in higher animals is uniparental Reason R: The mitochondria from the male partner either undergo degeneration or rejected and only mitochondria from egg or ova is accepted. (a) Assertion and Reason are correct Reason is explaining assertion (b) Assertion and Reason are correct, but the reason is not explaining assertion (c) Assertion is true but Reason not explaining assertion (d) Assertion is true but Reason is wrongv

Solution

a) Assertion and Reason are correct. Reason is explaining assertion

Answer:

a) Assertion and Reason are correct. Reason is explaining assertion

Q.1See the diagram & label the partsv

Solution

A – Leptotene
B – Chromosomes are visible under a light microscope
C – Paired sister chromatids begin to condense

Answer:

A – Leptotene
B – Chromosomes are visible under a light microscope
C – Paired sister chromatids begin to condense

Q.1Name the two types of nuclear division.v

Solution

The two types of nuclear division:
* Mitosis and
* Meiosis.

Answer:

The two types of nuclear division:
* Mitosis and
* Meiosis.

Q.1Write down the significance of Meiosis.v

Solution

Maintain chromosome number constant
Crossing over (exchange of genetic meterial) leads to variations
Variation – the raw material for Evolution
Finally, meiosis produces genetic variability by partitioning different combinations of genes into gametes through an independent assortment.
Responsible for Adaptations of organisms to various environmental stress.

Answer:

Maintain chromosome number constant
Crossing over (exchange of genetic meterial) leads to variations
Variation – the raw material for Evolution
Finally, meiosis produces genetic variability by partitioning different combinations of genes into gametes through an independent assortment.
Responsible for Adaptations of organisms to various environmental stress.

Q.1Explain in detail the various stages of Prophase I.v

Solution

The various stages of Prophase I:
1. Prophase I – Prophase I is of longer duration and it is divided into 5 substages – Leptotene, Zygotene, Pachytene, Diplotene and Diakinesis.
2. Leptotene – Chromosomes are visible under light microscope. Condensation of chromosomes takes place. Paired sister chromatids begin to condense.
3. Zygotene – Pairing of homologous chromosomes takes place and it is known as synapsis. Chromosome synapsis is made by the formation of synaptonemal complex. The complex formed by the homologous chromosomes are called as bivalent (tetrads).
4. Pachytene – At this stage bivalent chromosomes are clearly visible as tetrads. Bivalent of meiosis I consists of 4 chromatids and 2 centromeres. Synapsis is completed and recombination nodules appear at a site where crossing over takes place between non – sister chromatids of homologous chromosome. Recombination of homologous chromosomes is completed by the end of the stage but the chromosomes are linked at the sites of crossing over. This is mediated by the enzyme recombinase.
5. Diplotene – Synaptonemal complex disassembled and dissolves. The homologous chromosomes remain attached at one or more points where crossing over has taken place. These points of attachment where ‘X’ shaped structures occur at the sites of crossing over is called.
6. Chiasmata: Chiasmata are chromatin structures at sites where recombination has been taken place. They are specialised chromosomal structures that hold the homologous chromosomes together. Sister chromatids remain closely associated whereas the homologous chromosomes tend to separate from each other but are held together by chiasmata. This substage may last for days or years depending on the sex and organism. The chromosomes are very actively transcribed in females as the egg stores up materials for use during embryonic development. In animals, the chromosomes have prominent loops called lampbrush chromosome.
7. Diakinesis – Terminalisation of chiasmata. Spindle fibres assemble. Nuclear envelope breaks down. Homologous chromosomes become short and condensed. Nucleolus disappears.

Answer:

Q.2Most nëurons remain in G-’o’ stage do not divide (I) This technique can be applied to replace neurons in dementia patients (II) neurons can be activated by giving electric shocks (III) neurons can be replaced by surgical procedures (IV) Dead or injured neurons can be replaced by stem cell therapyv

Solution

(IV) Dead or injured neurons can be replaced by stem cell therapy
V.

Answer:

(IV) Dead or injured neurons can be replaced by stem cell therapy
V.

Q.2(I) Cell cycle – A) division that follows the nuclear division (II) Restriction point – B) Longest part but not resting stage (III) lnterphae – C) A series of events leading to the formation of a new Cell (IV) Cytokinesis – D) The checkpoint at the end of Gi determine a cell’s fatev

Solution

c) C-D- B- A
VI.

Answer:

c) C-D- B- A
VI.

Q.2Assertion A: In Meiosis Prophase I is a longer but significant phase Reason R: Chiasma formation and crossing over takes place and recombination takes place (a) Assertion and Reason are correct Reason is explaining Assertion (b) Assertion and Reason are correct but Reason is not explaining Assertion (c) Assertion is true but Reason is wrong (d) Assertion is true but Reason not explaining Assertionv

Solution

b) Assertion and Reason are correct but Reason is not explaining Assertion

Answer:

b) Assertion and Reason are correct but Reason is not explaining Assertion

Q.2See the diagram and write the correct answer. A B C D a) Cell growth interphase Mitotic phase Cyto kinesis b) Interphase Cell growth Mitotic phase Cytokinesis c) Cell growth Inter Phase Cytokinesis Mitotic phase d) Interphase Cell growth Cytokineses Mitotic phasev

Solution

a) Cell growth – Interphase – Mitotic phase – Cyto kinesis

Answer:

a) Cell growth – Interphase – Mitotic phase – Cyto kinesis

Q.2What are the reasons for the arresting growth of cell during G1 Phase?v

Solution

Deprivation of nutrition
Lack of growth factors or density-dependent inhibition occur
Some metabolic changes leads to Go – stage

Answer:

Deprivation of nutrition
Lack of growth factors or density-dependent inhibition occur
Some metabolic changes leads to Go – stage

Q.2Differentiate between Mitosis in Plants & Animals.v

Solution

Plants
Animals
Centrioles are absent
Centrioles are present
Asters are not formed
Asters are formed
Cell division involves the formation of a cell
Cell division involves furrowing and cleavage of cytoplasm
Occurs mainly at the meristem
Occurs in tissues throughout the body

Answer:

Q.2Explain karyokinesis in mitosis of plant cellv

Solution

Prophase – Longest Phase
* Chromosomes visible thread like condenses into thick chromosomes
* Initiation of spindle fibres occur
* Nucleolus disappear Nuclear envelope breaks down
* Golgi apparatus & ER not seen
Metaphase
* Sister chromatids attached to spindle fibres by kinetochore of centromere
* Chromosome align on the equatorial plane (metaphase plate)
(spindle assembly check point decide the fate of the cell)
Anaphase
* Centromere split daughter chromatids move to opposite poles
* Shortening of spindle create pull divide centromere & divide chromosome into a chromatids
(APC /C leads to degradation of protein lead to separation of chromatids
Telophase
* Genetic material division completed Nucleolus & Nuclear membrane reform.
* Sister chromatids become thick chromosomes with its own centromere.

Answer:

Q.3Assertion A: Interphase is the longest part of cell division and the cell actively involved protein synthesis & DNA synthesis Reason: The Interphase is also known as the resting phase, & the cell takes rest between successive cell division (a) Assertion and Reason are correct Reason is explaining Assertion (b) Assertion and Reason are correct but Reason is not explaining Assertion (c) Assertion is true but Reason is wrong (d) Assertion is true but Reason not explaining assertionv

Solution

c) Assertion is true but Reason is wrong

Answer:

c) Assertion is true but Reason is wrong

Q.3See the diagram & label Find out the correct labelling. A B C D a) Chromatin Kineto chore See constriction Centromere b) Centromere Chromatin See constriction Kineto chore c) Centromere Kineto chore Chromatin Centomere d) Chromatin See Constriction Kineto chore Centomerev

Solution

b) Centromere – Chromatin – Secondary constriction – Kinetochore

Answer:

b) Centromere – Chromatin – Secondary constriction – Kinetochore

Q.3Point out the reasons responsible for the arresting of the cell in the G 1 phase?v

Solution

Cells are arrested in G 1 due to:
* Nutrient deprivation
* Lack of growth factors or density dependant inhibition
* Undergo metabolic changes and enter into G 0 state.

Answer:

Cells are arrested in G 1 due to:
* Nutrient deprivation
* Lack of growth factors or density dependant inhibition
* Undergo metabolic changes and enter into G 0 state.

Q.3Explain Endomitosis.v

Solution

Sometimes, the replication of chromosomes occur in the absence of karyokinesis & cytokinesis resulting in numerous copies within each cell condition known as Endomitosis.
* Chromonema donot separate to form Chromosomes
* Nuclear membrance does not repture
* No spindle formation occur
* Each chromosome consisting of over thousands of synapsed Chromatids
Eg – Salvary gland chromosome of Drosophila (Polytene or Chromosome).

Answer:

Q.3Explain S phase & G2 phase, til S Phasev

Solution

(i) S Phase:
* Known as synthetic phase of interphase of mitosis
* Growth of cell continues
* Replication of DNA occur
* Histones synthesised and attach to DNA
* Duplication of centrioles occur
* DNA content doubles from 2C to 4C
(ii) G2 phase
* 4 C amount of DNA
* Cell growth continues
* Synthesis of
* organelle,
* mitochondria & chloroplast
* tubulin synthesised, microtubules formed
* Spindle begin to occur
* Nuclear division follows
* MPF (Maturation Promoting factor) formed brings out condensation of interphase chromosomes into mitotic form.

Answer:

Q.4Assertion A: The sister chromatids of homologous chromosomes exchange chromosomal bits Reason R: This process of exchange of chromosomal bits is known as crossing over (a) Assertion and Reason are correct Reason is explaining Assertion (b) Assertion and Reason are correct but Reason is not explaining Assertion (c) Assertion is true but Reason is wrong (d) Assertion is true but Reason not explaining assertionv

Solution

d) Assertion is true but Reason not explaining assertion
VII.

Answer:

d) Assertion is true but Reason not explaining assertion
VII.

Q.4Label the diagram properly.v

Solution

A – Non-sister Chromatids
B – Centromere
C – Chiasma
D – Bivalent or Tetrad

Answer:

A – Non-sister Chromatids
B – Centromere
C – Chiasma
D – Bivalent or Tetrad

Q.4Differentiate between karyokinesis and Cytokinesis of Amitosis.v

Solution

Karyokinesis
Cytokinesis
Division of Nucleus occur
Division of Cytoplasm occur
Nucleus develop contraction at the centre become dumbbell shaped contriction deepen divide nucleus into two
Plasma membrane develop constriction along with nuclear contraction, which deepen centripetally and the cell divides into two

Answer:

Q.4Differentiate between Anaphase I & Anaphase II of Meiosis.v

Solution

5 Mark Questions

Answer:

5 Mark Questions

Q.5Define amitosis & write about its drawbacks.v

Solution

Amitosis is known as Direct cell division or Incipient cell division.
No spindle formation, no condensation of chromatin material occur.
It has one 2 steps
* Karyokinesis
* Cytokinesis
Drawbacks: Causes unequal distribution of chromosomes Can lead to abnormalities in
* metabolism
* reproduction

Answer:

Q.5What are the significances of Mitosis.v

Solution

Exact copy of the parent cell is produced by mitosis (genetically identical).
* Genetic stability – Daughter cells are genetically identical to parent cells.
* Growth – As multicellular organisms grow, the number of cells making up their tissue increases. The new cells must be identical to the existing ones.
* Repair of tissues – Damaged cells must be replaced by identical new cells by mitosis.
* Asexual reproduction – Asexual reproduction results in offspring that are identical to the parent. Example Yeast and Amoeba.
* In flowering plants, structure such as bulbs, corms, tubers, rhizomes and runners are produced by mitotic division. When they separate from the parent, they form a new individual. The production of large numbers of offsprings in a short period of time, is possible only by mitosis. In genetic engineering and biotechnology, tissues are grown by mitosis (i.e. in tissue culture).
* Regeneration – Arms of starfish

Answer:

Q.6Distinguish between Closed and Open mitosis.v

Solution

Closed mitosis
Open mitosis
Nuclear envelope remain intact & chromosomes migrate to opposite poles of a spindle with in the Nucleus
Eg – Unicellular Eukaryotes – Yeast, Slime molds
Nuclear envelope breaks down and then reforms around the 2 sets of separated Chromosome
Eg – Most higher Plants & Animals

Answer:

Q.7Differentiate between Anastral and Amphiastral cell divisionv

Solution

Anastral
Amphiastral
* Occur in plant cell
* No asters or centrioles are formed,
only spindle fibres are formed Eg. Plants
* Occur in animal cells
* Asters and centrioles formed at each pole of the spindle during cell division Eg. Animals

Answer:

Q.8What happens to plant cells at the end of Telophase in Mitosis?v

Solution

In plants, phragmoplast are formed between the daughter cells. A cell plate is formed between the two daughter cells, reconstruction of cell wall takes place. Finally, the cells are separated by the distribution of organelles, macromolecules into two newly formed daughter cells.

Answer:

Q.9Differentiate meiosis in Plants & Animals.v

Solution

Plants
Animals
In flowering plants meiosis occur during Microsporogenesis (anther) & in Mega sporogenesis (i.e) (ovule) development
It take place in reproductive organs at the time of production of gametes Spermatogenesis – produces haploid sperms Oogenesis – produces haploid eeas

Answer:

Q.10Define Mitogens.v

Solution

The biochemical substances or factors which promote cell cycle acceleration & proliferation is called Mitogen.
Eg. Gibberellin, Ethylene, Indole Acelic Acid, Kinetin.
They are also known as Growth promotors.

Answer:

The biochemical substances or factors which promote cell cycle acceleration & proliferation is called Mitogen.
Eg. Gibberellin, Ethylene, Indole Acelic Acid, Kinetin.
They are also known as Growth promotors.

Q.11Explain briefly about Endomitosis.v

Solution

The replication of chromosomes in the absence of nuclear division and cytoplasmic division resulting in numerous copies within each cell is called endomitosis. Chromonema do not separate to form chromosomes but remain closely associated with each other. Nuclear membrane does not rupture. So no spindle formation. It occurs notably in the salivary glands of Drosophila and other flies. Cells in these tissues contain giant chromosomes (polyteny), each consisting of over thousands of intimately associated, or synapsed, chromatids. Example: Polytene chromosome.
3 Mark Questions

Answer:

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