வேதநதி

CELL CYCLE & CELL DIVISION

A 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 B 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

Section-A

1.Cell division can not be stopped in which phase of the cell cycle?

$G_1$-phase
$G_2$-phase
S-phase
Prophase
Cell division cannot be stopped in S-phase. The S-phase is the synthesis phase, in which the cell synthesises a replica of its genome, i.e., DNA replication occurs which ultimately result in the duplication of chromosomal material.

2.In which stage of the first meiotic division, two sister chromatids are formed?

Leptotene
Zygotene
Pachytene
Diplotene
In pachytene substage of meiosis-I, the paired homologous chromosomes divide into sister chromatids. Thus, each bivalent is composed of four chromatids and known as tetrad.

3.Chiasma shows the sites of

Spindle formation
Synapsis
Crossing over
None of these
Chiasma is an attachment of two non-sister chromatids in a bivalent in diplotene stage of prophase-I of meiosis. Each chiasma results in the exchange of genetic material between non-sister chromatids, i.e., crossing over.

4.Select the correct statements regarding S-phase of interphase
I. Occurs between $G_1$ and $G_2$
II. DNA replication begins in the nucleus
III. Centrioles duplicate in the cytoplasm
IV. As DNA is doubled, number of chromosomes also doubles
The option with correct statements is

IV and III
I, II, III and IV
II, III and IV
I, II and III
S-phase is the sub-phase between $G_1$-phase and $G_2$-phase, during which DNA synthesis or replication takes place.
In animal cells, during the S-phase, DNA replication begins in the nucleus and the centriole duplication in the cytoplasm. The amount of DNA per cell doubles in the nucleus. If the initial amount of DNA is denoted as 2C, then it increases to 4C. However, there is no increase in the chromosome number

5.Which is correct for meiotic metaphase-I?

Bivalents are arranged at equator
Univalents are arranged at equator
Non-homologous chromosomes forms pair
Spindle fibres are attached at chromomere
In meiotic division metaphase-I spindle apparatus starts appearing and bivalents become attached to spindle through centromeres. Bivalents then appear in the form of an equatorial plate due to the movement known as ‘congression’

6.Significance of meiosis lies in

Reduction of chromosome number to one half
Maintaining consistency of chromosome number during sexual reproduction
Production of genetic variability
All of the above

7.RNA and proteins are formed in

$G_1$-phase
$G_2$-phase
S-phase
$G_0$-phase
The main events which take place in $G_1$-phase are:
Intensive cellular synthesis,
Pooling of nucleotides for synthesis of rRNA.
Synthesis of enzymes and ATP storage,
Synthesis of NHC protein, carbohydrates, liquids, etc.

8.In _A_. phase, there is synthesis of RNAs and proteins that are needed for cell growth and replication of DNA. While it is _B_ phase, where synthesis of protein occur that is needed for spindle formation and mitosis to continue.
Identify A and B to complete the given statement

A-G; B-S
A-$G_2$; B-S
A-G; B-$G_2$
None of these
$A-G_1;B-G_2$

9.An egg cell has 5 picogram of DNA in its nucleus. How much amount of DNA will be, in this animal, at the end of $G_2$-phase of mitosis?

2.5 picogram
5 picogram
5 g
20 picogram
Egg is haploid and has 5 pg (picogram) DNA. Its animal, which is diploid will be having 10 pg DNA. In S-phase, DNA doubles and therefore, in $G_2$ amount of DNA will be 20 pg.

10.Crossing over is also an enzyme mediated process and the enzyme involved is called

Ligase
Polymerase
Recombinase
Endonuclease
Crossing over is also an enzyme mediated process and the enzyme involved is called recombinase

11.Mitosis is characterized by

Reduction division
Equal division
Both Reduction and Equal division
Absence of spindle formation
M-phase (mitosis) is the most important period of cell cycle. It involves a major recognisation of virtually all components of the cell. Since, the number of chromosomes in the parent and progeny cells is the same, it is also called as equal division

12.From the following, identify the two correct statements with reference to meiosis
I. Bead-like structures are absent on chromosomes
II. Displacement of chiasmata occurs in diakinesis
III. Separation of two basic sets of chromosomes
IV. No division of centromere
The correct option is

II and III
II and IV
III and IV
I and III
In meiosis-I, displacement of chiasmata takes place in diakinesis and homologous chromosomes segregates during anaphase-I

13.What type of cell division takes place in the functional megaspore initially in angiosperms?

Homeotypic without cytokinesis
Reductional without cytokinesis
Somatic followed by cytokinesis
Meiotic followed by cytokinesis
Initially, homeotypic cell division takes place in the functional megaspore without cytokinesis.

14.If you are provided with root-tips of onion in your class and are asked to count the chromosomes, which of the following stages can you most conveniently look into?

Metaphase
Telophase
Anaphase
Prophase
At metaphase, the chromosome are clearly visible as composed to two closely associated halves (chromatids) and the chromosomes have undergone maximum contraction, so these can be counted conveniently.

15.Which of the following character is related with telophase?

Formation of nuclear membrane
Formation of nucleolus
Elongation of chromosome
Formation of two daughter nuclei
During telophase, the chromatids have reached the poles of the cell, uncoil and lengthen to form chromatin again. The spindle fibres disintegrate and centriole replicate. Nucleoli and nuclear envelope reappear and hence, two daughter nuclei are formed at each pole.

16.Which of the following statements are correct for $G_1$-phase?
I. It is the last substage of interphase
II. Cell organelles do not increase in number
III. Both cell and nucleus grow in size
IV. It synthesizes RNAs, proteins and other biochemical for cell growth and subsequent replication of DNA
Choose the correct option

I and II
II and IV
I and III
II and III
The last substage of interphase is $G_2$-phase in $G_2$-phase, cell organelles increases in number and both cell and nucleus grows in size
$G_1$-phase, is the first stage of interphase during which cell organelles do not increase in number. Cell grows in size but the growth of nucleus is little. It synthesizes RNAs, proteins and other biochemical for cell growth and subsequent replication of DNA

17.What is the nature of cells formed at the end of meiosis-II?

Haploid
Diploid
Tetrad
None of these
Reduces by half.
Meiosis start with one diploid containing copies of chromosome, one from mother and one from father. The cell divides twice, producing up to four haploid cells containing one copy of each chromosome

18.In meiosis, chromosome number becomes

Half of its parent chromosome
Same as that of parent chromosome
One fourth of its parent chromosome
None of the above
In meiosis (meiotic-I), chromosome number becomes half to that of parent chromosome.

19.The two chromatids of a metaphase chromosome represent

Replicated chromosomes to be separated at anaphase
Homologous chromosomes of a diploid set
Non-homologous chromosomes joined at the centromere
Maternal and paternal chromosomes joined at the centromere
The two chromatids of a metaphase chromosome represent replicated chromosomes to be separated at anaphase

20.In plant cell has 12 chromosomes at the end of mitosis. How many chromosomes would it have in the $G_2$-phase of its next cell cycle?

6
8
12
24
In $G_2$-phase chromosome number remains same, so the right answer is 12 chromosomes.

21.Chromatid formation takes place in

S-phase
Metaphase
$G_1$-phase
$G_2$-phase
Interphase of cell cycle is composed of $G_1$-phase, $G_2$-phase and S-phase. During S-phase, DNA replicates in semi conservative manner so, each chromosome is formed of two chromatids joined at centromere.

22.DNA replicates

Twice in each cell cycle
Only once in each cell cycle
Once in mitotic cell cycle, once in meiotic-I (reductional division) and once in meiotic-II (equational division)
None of the above
DNA replicates only once in each cell cycle (S-phase)

23.In which stage of cell division, chromosomes are most condensed?

Prophase
Metaphase
Anaphase
Telophase
In metaphase, chromosomes are shortest and show maximum condensation. Chromosomes are arranged at equatorial metaphasic plate. Structure, size and number of chromosomes are best studied at metaphase.

24.Choose the correct sequence of two main events in mitosis

Karyokinesis followed by cytokinesis
Cytokinesis followed by karyokinesis
Karyokinesis followed by separation of the daughter cells
Cytokinesis followed by separation of the daughter cells
There are two main events in mitosis, karyokinesis or duplication of the nucleus, followed by division of the cytoplasm called cytokinesis. This is followed by the separation of the daughter cells

25.Replication of centriole occurs during

Interphase
Prophase
Late prophase
Late telophase
Interphase has three phases-$G_1$, S and $G_2$. Replication of centriole occurs during $G_1$-phase of interphase. DNA replication takes place in S-phase of interphase.

26.Which of the following statement is true for cells in $G_0$ stage of cell cycle?

Cells in $G_0$ stage are metabolically more active
Cells are metabolically inactive
Cells are metabolically active but no longer proliferate in normal condition
None of the above
During the $G_0$-phase, cells are metabolically active but no longer proliferate in normal condition

27.Crossing over is the exchange of genetic material between

Non-sister chromatids of the homologous chromosomes
Sister chromatids of the homologous chromosome
Chromatids of non-homologous chromosomes
The genes those are completely linked
Crossing over is a process that produces new combination of genes by interchanging of segments between non-sister chromatids of homologous chromosomes. It occur between homologous chromosomes at four stranded stage during pachytene of prophase-I of meiosis-I.

28.Which of the following occurs more than one and less than five in a chromosome?

None
Chromomere
Centromere
Telomere
Telomeres are the ends of chromosomes. These are required for the individuality of chromosomes. Generally, these are present more than one and less than five in a chromosome.

29.Which stages of cell division do the following figures ‘A’ and ‘B’ represent respectively?

A-Metaphase,B-Telophase
A-Telophase,B-Metaphase
A-Late anaphase,B-Prophase
A-Prophase,B-Anaphase
Late anaphase is characterised by
(i) Centromeres split and chromatids separate
(ii) Chromatids move to opposite poles.
Prophase is characterised by centriole separation.

30.In cell cycle, during which phase chromosomes are arranged at equatorial plate?

Metaphase
Anaphase
Telophase
Prophase
Metaphase in both mitosis and meiosis is characterised by the orientation of chromosomes themselves on the spindle fibres at the equatorial plate.

31.Which of the following statement(s) is/are not correct about meiosis?
I. Meiosis involves pairing of homologous chromosomes and recombination between them
II. Two diploid cells are formed at the end of meiosis-II
III. Meiosis involves two sequential cycles of nuclear and cell division called meiosis-I and meiosis-II, but only a single cycle of DNA replication
IV. Meiosis-I is initiated after the parental chromosome replication which produce identical sister chromatids at the S-phase
The correct option is

I and III
II only
II and III
I, II, III and IV
During meiosis, four haploid cells are produced by reductional division from a single diploid cell. Parent cell contains replicated chromosomes, but the daughter cells contains unreplicated chromosomes

32.Which of the following statements (events) is/are true for mitotic telophase?

Nucleolus, GB and ER form
NM assembles around each chromosomes clusters
Arrival of chromosomes cluster at opposite poles and loss of their identity as discrete elements
All of the above
Telophase is the reverse stage of prophase. During this phase, the cytoplasmic viscosity decreases and the two chromosome groups reorganize themselves into nuclei. A nucleae envelope appears outside the nucleoplasm collected in the area of chromatin. Spindle fibres disappear around the poles and Golgi complex and endoplasmic reticulum are reformed

33.Chromosome reaches their respective poles in which of the following stages of mitosis?

Cytokinesis
Interphase
S-phase
Telophase
At the beginning of the final stage of mitosis, i.e., telophase, the chromosomes that have reached their respective poles, decondense and lose their individuality. The individual chromosomes can no longer be seen and chromatin material tends to collect in a mass in the two poles . This is the stage which shows the following key events

34.In $G_1$-phase of cell cycle, what would be the change in DNA content of the cell?

DNA content increases to double
DNA content gets reduced
Four fold increase of DNA content
No change in DNA content
$G_1$-phase corresponds to the interval between mitosis and initiation of DNA replication. During $G_1$-phase, the cell is metabolically active and continuously grows but do not replicate its DNA

35.I. The cells that do not divide further, exit $G_1$-phase to enter an inactive stage called -A- phase of the cell cycle
II. The cells that are in $G_2$-phase definitely continue with the -B- phase.
Identify A and B to complete the given NCERT statements

$A-G_0; B-S$
$A-S; B-G_0$
$A-M; B-G_0$
$A-G_0; B-M$
$A-G_0; B-M$

Section-B

36.Sequence of four phases of cell cycle is

$G_1 →S →G_2→M$
$G_1 →G_2 →S→M$
$S→G_1 →G_2→M$
$M→G_1 →G_2→S$
The correct sequence of cell cycle phases is $G_1 →S →G_2→M$.

37.Which of the following type of cell cycle is known as equational division?

Amitosis
Mitosis
Meiosis
None of the above
Mitosis divides the parent cell into two identical daughter cells, each with a nucleus having the same amount of DNA, the same number and kind of chromosomes and the same heredity instructions as the parent cell, that’s why it is called as the equational division

38.Mitotic stages are not observed in

Cosmarium
E.coli
Saccharomyces
Chlorella

39.Which of the following statements are correct for multicellular cell division?
I. Cell division brings about embryonic development and growth
II. It plays a role in repair and maintenance of the body
III. It is important for reproduction
The correct option is

Only I
I and III
Only II
I, II and III
In multicellular organisms, cell division brings about embryonic development and growth and also plays an important role in repair and maintenance of the body and also in reproduction, both asexual and sexual

40.Colchicine arrests which of the following stage of cell division?

Prophase
Anaphase
Telophase
Metaphase
Colchicine prevents spindle formation, which occurs during metaphase stage of cell division.

41.Choose the correct combination of options to select the correct statement for prophase
I. Chromosomal material condenses to form compact mitotic chromosomes
II. The assembly of mitotic spindle is initiated by the microtubules
III. Cells do not show organelles when viewed under the prophase
IV. The nucleolus or nucleoli degenerate completely

I only
II and III
I and II
All of these
At the end of prophase, several characteristic events can be observed. Chromosomal material condenses to form compact mitotic chromosomes. Two chromatids attach together to form chromosomes
Assembly of mitotic spindle is initiated by, microtubules (proteinaceous components) of the cell cytoplasm. When observed under the microscope cells at the last stage of prophase, do not shows cell organelles like, Golgi complexes, endoplasmic reticulum, nucleolus and the nuclear envelope

42.Synapsis occurs between

A male and a female gamete
mRNA and ribosomes
Spindle fibres and centromere
Two homologous chromosomes
In zygotene of prophase-I, homologous chromosomes pair up. This process is called synapsis. One chromosome of the pair is from the male parent and other from the female parent.

43.Which of the following shows diplotene stage of cell cycle?

Separation of synapsed homologous chromosomes except at the site of cross overs
Degenecation of nucleolus
Chiasmata shift towards cheromosome ends
All of the above
The beginning of diplotene stage is marked by chiasma formation. The chiasma formation is the indication of crossing over and the beginning of separation of chromosomes.
The chiasma formation is associated with the process of terminalisation

44.The stage between two meiotic division is called

Interphase
Cytokinesis
Interkinesis
Karyokinesis
The stage between two meiotic divisions is called interkinesis. It is generally short lived and is followed by prophase-II, a much simpler prophase than prophase-I of meiosis-I.

45.Arrange the following events of meiosis in the correct sequence.
1. Terminalization
2. Crossing over
3. Synapsis
4. Disjunction of genomes
The correct sequence is

4, 3, 2, 1
3, 2, 1, 4
2, 1, 4, 3
1, 4, 3, 2
The correct sequence is:
Synapsis→Crossing over→Terminalization→ Disjunction of genomes

46.Chromosome number can be doubled by using which of the following?

Indole acetic acid
GA
Zeatin
Colchicines
Colchicine treatment doubles the chromosome number.

47.What would be the change in the chromosome number, during S-phase?

No change
The number of chromosome doubles
The number of chromosome doubles only in case of diploid cell
The number of chromosome doubles only in case of haploid cell
During S-phase, there is no increase in the chromosomes number. If the cell has diploid or 2n number of chromosomes at $G_1$, even after S-phase the number of chromosomes remains the same, i.e., 2n

48.The major event that occurs during the anaphase of mitosis, which brings about the equal distribution of chromosomes is

Replication of the genetic material
Splitting of the chromatids
Splitting of the centromeres
Condensation of the chromatin
Anaphase is characterised by splitting of the centromeres and separation of chromatids. Chromatids move to opposite poles from the equatorial plates

49.Which of the following is unique to mitosis and not a part of meiosis?

Homologous chromosomes behave independently
Chromatids are separated during anaphase
Homologous chromosomes pair and form bivalents
Homologous chromosomes crossover
During mitosis, all the chromosomes behave independently while during meiosis, homologous chromosomes pair up through synapsis and form bivalents in zygotene substage of prophase-I, then in pachytene substage, crossing over occurs between homologous chromosomes and during diplotene substage of prophase-I of meiosis chiasma formation takes place.
During anaphase of both mitosis and meiosis, chromatids are separated and pulled towards opposite poles.

50.During mitosis, number of chromosomes gets

Change
No change
May be change if cell is mature
May be change if cell is immature
Mitosis was first observed by Strasburger and termed by W Flemming. During mitosis, chromosome number remain same in the daughter cells. During meiosis (reduction division), the chromosome number reduced to half in the daughter cells.