11 Cell cycle and division II
2nd Term WS 13
1
(a) Metaphase 1m
(b) Y
→ X → Z → W 1m
(c) The
cells have no cell wall. 1m
(d) The
chromosomes are not in homologous pairs. /
Only two
cells are produced in stage W. /
No
chiasmata are formed between chromosomes. (any 2) 1m x 2
2
(a) R
® S ® Q ® T ® P 3m
(b) The
DNA content of the cell at stage R is double that in a cell at stage P. 1m
After stage R, the chromosomes in
the cell separate into two equal groups 1m
and each group goes to a daughter
cell. 1m
As chromosomes are made up of DNA,
mitotic cell division reduces
the DNA content of the cell at
stage R by half. 1m
(c) To
produce new cells for growth. 1m
To
produce new cells for replacing worn-out or damaged cells. 1m
For asexual reproduction in some
organisms to produce offspring. 1m
3
(a) (i) Chromosomes were / chromatin /
nucleus was visible after staining. /
Staining enabled the determination
of different stages in mitosis / cell cycle. /
Staining provided contrast between
cell structures. (any 2) 1m x 2
(ii) Mitosis 1m
(b) 4.34%
+ 3.23% + 3.23% + 7.20% 1m
= 18% 1m
OR
100% – 82% 1m
= 18% 1m
(c) In
meiosis, the cells produced are not genetically identical. /
In meiosis, the cells produced have only one
set of chromosomes / are haploid. /
In meiosis, the cells produced are gametes. /
In meiosis, four cells are produced. 1m
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