CELL DIVISION WITH MADAM HIDAH

1. (a) FIGURE 1.1 shows a Cell cycle and one of the stages in mitosis, B.

FIGURE 1.1

(i) Name the mitotic stage shown in B. Shade the area on the Cell cycle the stage

represented by B in FIGURE 1.1. [2 marks]

Anaphase

(ii) State the chromosomal behaviour shown in B. [1 mark]
Sister chromatids separate/move to opposite poles

(iii) Give one (1) important event thal occurs during S phase in the Cell cycle. [1 mark]
DNA/chromosome replication/synthesis/ duplication

(iv) A cat has 38 chromosomes in its somatic cell. How many chromosomes are inherited

from the female parent? Explain your answer. [2 marks]

▪ 19

▪ Meiosis reduces the chromosome number in gamete half from parental cell // To

ensure that zygote produced by the fusion of gametes contain the same number

of chromosomes as the parental cell.

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(b) FIGURE 1.2 shows the various stages, A - F in meiosis.

(i) Arrange the stages of meiosis, A- F shown in FIGURE 1.2 according to the correct

sequence. [1 mark]

C,E,D,B,F,A

(ii) Which of the stages in FIGURE 1.2 represents anaphase I? Give your reason.
[2 marks]

Homologous chromosomes separate /move to opposite poles

(iii) What happens to the number of chromosomes at the end of meiosis? [1 mark]
Haploid/ n//Number of chromosome is being halve

2 (a) FIGURE 2.1 shows a cell eycle.

FIGURE 2.1
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(i) Name phase P. [1 mark]
Interphase

(ii) Describe the events that occur in phase Q. [2 marks]

▪ Cells grows/ cell increase in size/ cytoplasmic volume increases

▪ Cell produce macromolecules/ protein/ lipid/ carbohydrate/ enzyme

▪ Increase in number of organelles // synthesis of organelles (such as mitochondria and

endoplasmic reticulum

(iii) Explain the importance of phase R. [3 marks]

▪ To allow/maintain the same number of chromosomes in daughter cells (as the parent cell

after cell division/ mitosis)
▪ DNA is replicated/ duplicated // Histones are synthesize to allow DNA synthesis to occur
▪ To double the genome/ increase the amount of DNA/ chromosomes

(b) FIGURE 2.2 shows two types of cells, L and M.

FIGURE 2.2
(i) Name the event of cell division that occurs in both types of cells in FIGURE 3.2. [1 mark]

Cytokinesis

(ii) Differentiate process 3(b)(i) between cell L and M. [2 marks]

▪ Cell L forms the cell plate while cell M forms cleavage furrow

▪ Cell plate is formed by vesicles while cleavage furrow is formed by microfilament/actin

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▪ Cell plate enlarges and fuses to plasma membrane while cleavage furrow deepens and
pinches off

3 FIGURE 3 shows different stages of cell division in P and Q. The alleles G, g, H, h occupy the
loci on the chromosome.

FIGURE 3

(a) Give the name and function of structure S. [2 marks]

Name : Centriole

Function : Involve in the formation of spindle fiber / organize microtubule to
form spindle fiber

(b) Identify the stage of cell division in P and Q. [2 marks]

P : metaphase I

Q : metaphase

(c) Give three (3) differences of cell division in P and Q. [3 marks]

P Q 1/0

Nucleus divides twice / cell division Nucleus divides once/ cell division 1/0
/cytokinesis occurs twice /cytokinesis occurs once 1/0

Four daughter cells are formed Two daughter cells are formed

Daughter cells are haploid// number of Daughter cells are diploid// number
chromosome reduce to half of chromosome remain the same

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Synapsis occur Synapsis does not occur 1/0
1/0
Crossing over occurs// chiasma forms Crossing over does not occurs// no
chiasma 1/0

Homologous chromosome / bivalent Chromosome / sister chromatid

/tetrad align at metaphase plate/ equator align at metaphase plate/ equator

(d) What is the allele combination for each daughter cell after the completion of cytokinesis

in P and Q? [2 marks]

P : GH and gh

Q : GgHh

No Suggested Answer
4(a)
Comparison
4(b)
Mitosis Meiosis II

DNA replication occurs No DNA replication

Chromosomes become condense Chromosomes already condensed

and visible

Daughter cell are diploid (2n) // Daughter cell are haploid (n) //

Daughter cells have the same Daughter cells have the half

number of chromosomes as the number of chromosomes of the

parent parent

Occurs in somatic cells Occurs in reproductive cells

Daughter cell genetically Daughter cell genetically

identical to parental cells // different from parental cells //

Daughter cell genetically Daughter cell genetically

identical to each other different from each other

Two daughter cells are produced Four daughter cells are produced

Similarities
No chiasmata occurs // no crossing over
No pairing of homologous chromosomes
Individual chromosomes with two sister chromatids line up at spindle equator
Division of centromere during anaphase
Sister chromatids pulled to opposite poles during anaphase
Cytokines occurs at the end of the process
i. During anaphase I, the microtubules start to shorten
ii. Due to the concentration of spindle fibers
iii. The ( paired ) homologous chromosomes separate
iv. Causing the chiasmata to break
v. The sister chromatids are united at their centromere regions // no division of
centromere

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vi. And migrate towards opposite poles
vii. Due to the random orientation of homologous chromosomes on the metaphase plate

//due to the independent assortment.
viii. Each pole receives recombination / mixture of a set of parental chromosomes
ix. Thus, contributes to the genetic variation.

5 (a) Mitotic cell division which occurs in all eukaryotic cells occupies the shortest period of
the cell cycle. Describe the events of all phases in mitotic cell division. [12 marks]

Suggested Answer

Prophase
Nuclear envelope disintegrate// nucleolus disintegrate
Chromosomes shorten and thicken / condense(and become visible)
Two sister chromatids are joined / attached at the centromere
Spindle fibres/ microtubules begin to form // aster begin to form
Metaphase
Chromosomes arranged themselves on the equatorial / metaphase plate
Kinetochore forms at the centromere// Centrosome arrived at the opposite poles of the cell
Microtubules / spindle fibres attach to kinetochore/centromere
Anaphase
Microtubules/ spindle fibres begin to contract
Centromere split
Two sister chromatids begin to separate/part
Chromatids begin to move to opposite poles

Telophase
Chromosomes arrive at the opposite poles of the cell
Nuclear envelope reappear//nucleolus reappear
Microtubules/spindle fibres depolymerised/ disappeared /disintegrate
Chromosomes become less dense/ uncondense

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(b) Compare mitotic cell division in plant and animal cells. [8 marks]

Suggested Answer

Similarities
Involve four phases
Both occur in somatic cells
Produce identical/similar two daughter cells
Differences

Cell division in plant cell Cell division in animal cell
Formation of cell plate
During telophase, cell plate is formed Formation of cleavage furrow
from vesicles During telophase, contractile ring is
formed from microtubules/ actin
Only occurs in meristematic cells filaments
Absence of aster Occur in all cells
Presence of aster

6. (a) Describe the behaviour of chromosomes during mitosis. [8 marks]

i. During (early) prophase, chromatin begin recoil/becoming shorter and thicker // during

(early) prophase chromosomes condensed

ii. Chromosome become visible

iii. Each chromossome consists a pair of sister chromatids which are joined at the centromere

iv. The chromosome centromeres are attached to the spindle fibres

v. At the (end of) prophase, chromosomes move towards the equator of the cell

vi. At metaphase, chromosomes lined up at the equator/equatorial/ metaphase plate

vii. At anaphase, the sister chromatids seperate and move to opposite poles of the cell

viii. At telophase, the (two groups) of (daughter) chromosomes /seperated sister chromatids

reached the opposite poles

ix. At the (end of) telophase, the chromosomes decondence/uncoiled/ lengthen and form (a

mass) of chromatin again

x. Each pole consists of a complete set of chromosomes enveloped in a new nucleus

(b) Explain the differences between mitosis and meiosis. [12 marks]

Mitosis Meiosis
Occurs in somatic cells Occurs in germ/oogonium and
spermatogonium/megaspore mother
Concist of a single division//nucleus divides// cells/microspore mother cells/megasporocyte/
cytokinesis division//nucleus divides/ microsporocyte/germinal epithelial cells
Consists of two successive division//nucleus
divides/cytokinesis occur twice

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Pairing of homologous chromosomes/ synapsis Pairing of homologous chromosomes/synapsis
does not occur occurs
Does not form bivalent/tetrad Formed bivalent/tetrad
Separation of sister chromatids Separation of sister chromatids occur at
occur at anaphase/separation anaphase II/ separation of homologous
of sister chromatids only chromosome and sister chromatids
Chromosome/sister chromatids align at the Homologous
metaphase plate during chromosome/bivalent align at metaphase plate
metaphase during metaphase I and
chromosome/sister chromatids align at
Crossing over/chiasmata does not occur metaphase plate during metaphase II
Produces (two) diploid (2n) Crossing over/chiasmata occurs
daughter cells// number of Produces (four) haploid
chromosomes same as parent daughter cells// number of
Daughter cells are identical to parent// daughter chromosome is halved
cell are genetically identical Daughter cells may be different due to crossing
over// daughter cell are genetically varied

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