21 Cell division and chromosomes
1 A cell in the basal layer of the skin contains 46 chromosomes and divides by mitosis to
produce new skin cells. After ten successive divisions, how many chromosomes will the
basal cell have?
4.6
2 The drawings below depict stages in the mitotic division of a cell
(a) Write the letters in the order in which these stages occur.
(b) How many pairs of chromosomes are there in the cell? 23
(c) What is the diploid number of chromosomes in these cells? 46
3 Choose the most appropriate word to complete the sentence.
When chromosomes replicate, they produce ……... nuclei
tissues, nuclei, chromatids, somatic cells
4 In which three of the following cells is mitosis unlikely to occur?
a sperm cell, an epithelial cell of a villus, a hair cell, a cell in the red bone marrow, a red blood
cell, a lymphocyte, a cell in the basal layer of the skin a cell in the red bone marrow
5 An animal has 36 chromosomes in each of its body cells. How many of these chromosomes
came from its male parent? 18
6 Which pairs of chromosomes in the cell shown here
are homologous?
7 Fill in the missing words.
The ….. A ….. of a cell contains a fixed number of
chromosomes. Before mitosis, each chromosome
….. B ….. to produce two ….. C …...
8 The following drawings-show the sequence of events early in cell division.
(a) Is the division meiotic or mitotic?
(b) How do you know?
A
B
C
D
E
A
B
C
D
E
F
Self-assessment questions 21.01
