Class:
Name:
11
(
) Date:
Cell cycle and division
11.1 Chromosomes (Book 2, p. 11-5)

The genetic information of an organism is carried in (1) _______________ (deoxyribonucleic
acid) which is present in the (2) _______________ of a cell.

A DNA molecule coils around some special proteins to form a (3) _______________.
one chromosome (染色體)
DNA molecule coils into a
highly organized pattern
special protein
chromatids (染色單體)
centromere
(着絲點)
DNA molecule
A chromosome just before
cell division (×9000)
 Structure of a chromosome
Term
I
chromosome
II
chromatin (染色質)
III
chromatid
IV centromere
Explanation
a
the appearance of chromosome when the cell is not dividing.
It is very thin and cannot be seen clearly under microscope
b
a point at which a pair of chromatids joins
c
a structure found in the nucleus, which is made up of a DNA
molecule coiling up around proteins
d
I: (4) ___________

each of the two daughter strands of a duplicated chromosome
II: (5) ___________
III: (6) ___________
IV: (7) __________
Chromosomes exist in (8) _______________ in the body cells. Members of each pair of
chromosomes are called (9) _______________ chromosomes.
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1

A cell with two sets of chromosomes is a (10) _______________ (2n) (二倍體) cell. It is
produced by (11) _______________ cell division (有絲細胞分裂).

A cell with only one set of chromosomes is a (12) _______________ (n) (單倍體) cell. It is
produced by (13) _______________ cell division (減數細胞分裂).

Humans have (14) _______________ pairs or (15) _______________ chromosomes.

The 23rd pair is the (16) _______________ chromosomes.
 Go to …
Quick check
(Book 2, p. 11-7)
11.2 Chromosomes (Book 2, p. 11-8)

From one cell division to the next, a cell undergoes a sequence of events known as the
(1) _______________ _______________ (細胞週期).
A
What are the main stages of the cell cycle? (Book 2, p. 11-8)
first growth
phase (G1)
cytoplasmic
division
(2) _______________
_______________
synthesis
phase (S)
second
growth
phase (G2)
nuclear
division
(3) _______________
_______________
 The cell cycle

In each cell cycle, the cell spends most time on (4) _______________ _______________.

The (5) _______________ of the cell cycle varies with different types of cells.
B
What happens to the cell in different stages of the cell cycle?
(Book 2, p. 11-8)
1
Cell growth (Book 2, p. 11-9)

Cell growth is also called (6) _______________ (間期).
nuclear
membrane
During cell growth, chromosomes appear as a mass of
thin threads called chromatin, many biochemical activities
are taking place to prepare for (7) _______________.
2

chromatin
(DNA
replicated)
DNA molecules replicated
before division
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Phase
Event
First growth phase (G1)
New (8) _______________ and proteins are made.
Synthesis phase (S)
(9) ______________ ______________ are replicated.
Second growth phase (G2)
Energy stores increase. The cell grows to its maximum size.
2
Mitotic cell division

Mitotic cell division starts with (10) _______________ division followed by
(Book 2, p. 11-9)
(11) _______________ division.
i)
Nuclear division

(12) _______________ (有絲分裂) is the nuclear division in mitotic cell division.

During mitosis, the duplicate set of chromosomes is separated from the original set.

Each new nucleus receives (13) _______________ complete set of chromosomes so that two
identical (14) _______________ nuclei are formed.

Mitosis consists of four main stages:
chromosome
Stage 1 (15)_______________ (前期)

Chromosomes become visible. Each is seen to
consist of two chromatids held together at the
two identical
chromatids
centromere.

The nuclear membrane (16) _______________.
Stage 2 (17) _______________ (中期)

The chromosomes line up in the
(18) _______________ of the cell.
Stage 3 (19) _______________ (後期)

The (20) _______________ of each chromosome
separate and move to the opposite poles of the cell.

The cytoplasm starts to divide.
Stage 4 (21) _______________ (末期)

New (22) _______________ _______________
form around each set of chromosomes.

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The chromosomes uncoil to become chromatin again.
3
Misconception
Some students wrongly think that chromosomes replicate at prophase when they become visible
as thread-like structures. In fact, chromosomes replicate before cell division. They then shorten
and become visible at prophase.
ii)
Cytoplasmic division

Cytoplasmic division is also called (23) _______________ (胞質分裂).

The cytoplasm of the parent cell divides into two equal halves to form two cells.
Animal cells
C
Plant cells
Cell membrane constricts
Cell plate (細胞板) formed between the two
(24) _______________.
new nuclei grows (25) _______________.
What is the significance of mitotic cell division? (Book 2, p. 11-12)
Mitotic cell division is important for:

(26) ____________: it provides new cells for the growth of multicellular organisms.

repair: it provides new cells for replacing worn-out or damaged cells.

(27) ____________ reproduction (無性生殖): it occurs in some organisms to produce
offspring.
 Go to …
Practical 11.1
Examination of different stages of the cell cycle
(Book 2, p. 11-13; Practical Workbook for SBA 2, p. 11-1)
Practical 11.2
Investigation of the relative time required for each stage of the cell cycle
(Book 2, p. 11-13; Practical Workbook for SBA 2, p. 11-4)
Quick check
4
(Book 2, p. 11-14)
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11.3 Meiotic cell division (Book 2, p. 11-15)
A

How does meiotic cell division occur? (Book 2, p. 11-15)
Meiotic cell division reduces the (1) _______________ number by half and gives rise to
(2) _______________ haploid daughter cells which are genetically (3) ______________.

Meiotic cell division starts with nuclear division called (4) ______________ (減數分裂)
followed by cytoplasmic division. It consists of first meiotic division and second meiotic
division.
First meiotic division
a pair of homologous
chromosome
Stage 1 prophase I

Chromosomes become visible.

Members of each pair of (5) _______________
chromosomes pair up.

The (6) _______________ membrane disintegrates.
two chromatids
Stage 2 metaphase I

(7) _______________ _______________ line up in
the middle of the cell.
Stage 3 anaphase I

The two members of each
(8) _______________ _______________ separate
and move to opposite poles of the cell.

The cytoplasm starts to divide.
Stage 4 telophase I

New nuclear membranes form around each set of
chromosomes.
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5
Second meiotic division
Stage 5 prophase II

Nuclear membranes disintegrate again.
Stage 6 metaphase II

(9) _______________ line up in the middle of
the cells.
Stage 7 anaphase II

(10) _______________ separate and move to
opposite poles of the cells.

The cytoplasm starts to divide.
Stage 8 telophase II

New nuclear membranes form around each set
of chromosomes.

After (11) ______________ ______________
has completed, four (12) ______________ cells
are formed. Each cell has one member of each
homologous pair.

Chromosomes uncoil to become chromatin
again.
 Go to …
Practical 11.3
Examination of meiotic cell division
(Book 2, p. 11-15; Practical Workbook for SBA 2, p. 11-10)
6
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B
1
What is the significance of meiotic cell division? (Book 2, p. 11-18)
Meiosis produces haploid gametes (配子) for (13) _______________ reproduction (有性生殖),
so that the diploid number of chromosome can be restored (還原) at fertilization.
 Two haploid gametes combine to form a diploid zygote
2
The random distribution and (14) _______________ _______________ (獨立分配) of
chromosomes produce various genetic combinations in the gametes. The zygotes formed will
have different genetic combinations from their parents. This causes genetic variation among
individuals of the same species.
 Independent assortment of chromosomes in meiotic cell division
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 Go to …
Quick check
(Book 2, p. 11-20)
11.4 Comparison between mitotic and meiotic cell
divisions (Book 2, p. 11-21)
Mitotic cell division
Meiotic cell division
Number of cell division
(1) ______________
(2) ______________
Daughter
cell
Number
produced
(3) ______________
(4) ______________
Chromosome
number
(5) ______________ (2n)
(6) ______________ (n)
Genetic
material
(7) ______________
(8) ______________
______________ parent cell
______________ parent cell
and among daughter cells
and among daughter cells
(9) ___________ ___________
(10) ______________
Behaviour of
chromosomes
Pairing of homologous
Pairing of homologous
chromosomes does not occur
chromosomes occurs
Place of occurrence
Body cells
Gamete-producing cells in
Cell type
sex organ
Significance
Form cells for growth,
Form haploid gametes for
(11) ______________ and
(13) ______________
(12) ______________
reproduction;
reproduction
provide (14) ______________
variations that enhance the
survival of the species
 Go to …
Quick check
8
(Book 2, p. 11-22)
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Exercise
a
The diagram below shows the relative time spent by the two main stages of the cell cycle.
Y
X
i
Name stages X and Y.
(2 marks)
________________________________________________________________________
ii
List three biochemical activities occur during stage X.
(3 marks)
________________________________________________________________________
b
The drawings below show two nuclei from the root tip cell of two different plant species
during prophase of stage Y.
species Q
species P
i
In the nucleus of species P, one member of a pair of homologous chromosomes has been
shaded. Shade the other member of the pair.
ii
State the number of chromosomes in the following cells:
(1 mark)
(2 marks)
diploid cell of species P: ___________________
haploid cell of species Q: ___________________
iii
Name the phase that occurs immediately after prophase. Describe the behaviour of
chromosomes in this phase.
(2 marks)
________________________________________________________________________
________________________________________________________________________
Total: 10 marks
－ END －
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9
Answers
Ch 11 Cell cycle and division
11.1
1
DNA
2
nucleus
3
chromosome
4
c
5
a
6
d
7
b
8
pairs
9
homologous
10
diploid
11
mitotic
12
haploid
13
meiotic
14
23
15
46
16
sex
3
mitotic cell division
11.2
1
cell cycle
2
cell growth/interphase
4
cell growth
5
duration
6
interphase
7
division
8
organelles
9
DNA molecules
10
nuclear
11
cytoplasmic
12
Mitosis
13
one
14
diploid
15
prophase
16
disintegrates
17
metaphase
18
middle
19
anaphase
20
chromatids
21
telophase
22
nuclear membrane 23
24
inwards
25
outwards
26
growth
27
asexual
1
chromosome
2
four
3
different
4
meiosis
5
homologous
6
nuclear
7
homologous pairs 8
homologous pair
9
Chromosomes
10
Chromatids
11
cytoplasmic division
12
haploid
13
sexual
14
independent assortment
cytokinesis
11.3
11.4
1
1
2
2
3
2
4
4
5
diploid
6
haploid
7
same as
8
different from
9
body cell
10
gamete
11
repair
12
asexual
13
sexual
14
genetic
Exercise
a
b
i
X: cell growth / interphase; Y: Mitotic cell division
2m
ii
DNA replication
1m
protein synthesis
1m
organelles synthesis
1m
1m
i
ii
nucleus P: 6; nucleus Q: 6
2m
iii
Metaphase
1m
Chromosomes line up in the middle of the cell.
1m
10
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