Practise CAIE AS Biology 5.1 by tracing the mitotic cell cycle and connecting chromosome structure, stem-cell replacement and uncontrolled division to tissue growth and tumours.
During sperm formation in mammals, part of the structure of each chromosome is replaced with proteins called protamines. This replacement allows the DNA to be packaged much more densely than would otherwise be possible.
Which part of the chromosome is replaced by protamines?
centromeres
chromatids
histones
telomeres
Which diagrams show roles of mitosis?
1
4
3
1, 2, 3 and 4
1, 2 and 3 only
1 and 2 only
3 and 4 only
The contents of a daughter cell are compared to the parent cell after one cell cycle.
Which row is correct?
number of chromosomes
volume of cytoplasm
length of telomeres
increases
remains the same
decreases
increases
decreases
remains the same
remains the same
remains the same
remains the same
remains the same
decreases
decreases
Telomerase is an enzyme that adds nucleotides to telomeres.
Which statement about telomerase is correct?
A high concentration of telomerase in a cell damages genes during DNA replication.
A high concentration of telomerase in cancerous cells limits the rate of tumour growth.
The low concentration of telomerase in stem cells means that these cells can divide an unlimited number of times.
The low concentration of telomerase in body cells means that these cells can divide a limited number of times.
Which row is correct for stem cells?
can repair cells
can be involved in the
formation of phagocytes
yes
no
yes
yes
no
no
no
yes
Why does the white blood cell count increase in people with leukaemia?
More antibodies are required so there are more B-lymphocytes.
More lymphocytes are produced in bone marrow.
More memory cells are produced in plasma.
More T-lymphocytes are required to stimulate the immune system.