exam Q's Flashcards
In human cells, the tumour suppressor gene TP53 codes for a protein that interrupts the cell cycle if there
is any damage to the DNA and prevents the copying of damaged DNA.
Which of the stages, A to D, could TP53 interrupt the cell cycle?
b- G1 stage
what can be seen during prophases
dark bodies visible within nucleus
The eukaryotic cell cycle is regulated by three checkpoints. Mutations can occur in genes that
control the cell cycle checkpoints.
Scientists recorded observations of two different tissues.
i. In one tissue, the scientists found a genetic mutation that stopped the metaphase checkpoint from
working.
Suggest an abnormality the scientists might observe in the cells of this tissue.
incorrect number of chromosomes
Cells can be counted and analysed using a technique called flow cytometry. DNA in the cells is
stained with a fluorescent dye before analysis. The degree of fluorescence is dependent on the amount
of DNA present.
Suggest why the use of fluorescent dyes in flow cytometry is inappropriate when analysing red blood
cells.
they don’t have a nucleus so don’t have DNA
A transmission electron microscope image of a white blood cell was studied. It was concluded that the
cell had stopped dividing at the G2 checkpoint.
Suggest two observations that would have led to this conclusion.
-more DNA
-larger number of organelles
mitosis is involved in growth and repair of tissue
state two other roles
-asexual reproduction
-clonal expansion/ produce new stem cells
Another stage of meiosis is metaphase 1.
Explain how the organisation of homologous chromosomes during metaphase 1
increases genetic variation.
- independent / random,
assortment ✓ - (homologous
chromosomes) line up,
across the centre of the cell
/
on the equator ✓ - either one
of the homologous pair,
can end up, facing either
pole - each chromosome of the
homologous pair, is
genetically different
. Mitosis and meiosis are important in the life cycles of organisms.
Hydra is a small animal that lives in fresh water.
When conditions are not favourable, Hydra reproduces sexually. This often happens in the winter.
Cells in the body wall produce sperms and eggs by meiosis.
Large numbers of sperms are released into the water. These sperms can fertilise eggs from
different individuals. Each egg forms a tough outer coat, and can lie dormant at the bottom of the
water until conditions improve.
i. *Explain how sexual reproduction in Hydra leads to genetic variation in the offspring.
- offspring have alleles from more than one
parent - meiosis produces genetically unique gametes
- crossing over in prophase 1
- alleles swapped between non-sister
chromatids - independent assortment / random segregation
Cell Division and Specialisation
PhysicsAndMathsTutor.com
in italics):
o award the higher mark
where the Communication
Statement has been met.
o award the lower mark
where aspects of the
Communication Statement
have been missed. - The science content
determines the level. - The Communication
Statement determines the
mark within a level.
Level 3 (5–6 marks)
Explains in detail how sexual
reproduction leads to genetic
variation with reference to more than
one stage of meiosis and with
reference to Hydra.
There is a well-developed line of
reasoning which is clear and
logically structured. The information
presented is relevant and
substantiated.
Level 2 (3–4 marks)
Explains in some detail how sexual
reproduction leads to genetic
variation with reference to more than
one stage of meiosis OR with
reference to Hydra and one stage of
meiosis.
There is a line of reasoning
presented with some structure. The
information presented is in the mostpart relevant and supported by some
evidence.
Level 1 (1–2 marks)
Mentions more than one reason why
sexual reproduction leads to genetic
variation.
The information is basic and
communicated in an unstructured - in metaphase 1
- the sperm from one Hydra can fertilise an egg
from any other individual Hydra - the two Hydra can have different alleles
Plant growth requires the production of new xylem cells.
Describe how new xylem cells are produced.
(produced) in, meristems / cambium
✓
(by) differentiation (from stem cells)
✓
Bone marrow contains stem cells that can develop into erythrocytes, neutrophils and
lymphocytes.
Describe the changes that must occur inside these stem cells as they differentiate to form
erythrocytes.
synthesise (a lot of) haemoglobin (1)
remove nucleus (2)
Cells from an embryo can be used for medical research and for research on the development
of an organism.
Suggest three ways in which the use of embryonic stem cells in research has practical benefits to
biological knowledge.
(can be grown into different tissues
to) test how effective new medicinal
drugs are (1)
(can be grown into different tissues
to) test for side effects / toxicity of
new drugs (1)
(can be grown and) studied to see
how they develop into different cell
types (developmental research) (1)
Explain the benefit to plants of internal transport systems.
idea of diffusion from outer surface
not sufficient ✓
(transport system) ensures
molecules / nutrients / sugars /
water, reach all tissues s ✓
Fig. 22.2 shows a podocyte from the kidney. The many gaps between the microscopic
processes form fenestrations in the Bowman’s capsule.
i. Explain why podocytes are usually unable to undergo mitosis.
1 have already / are, differentiated /
specialized (so cannot divide) ✔
3
max
Cell Division and Specialisation
PhysicsAndMathsTutor.com
2 are in, G0 (phase of cell cycle) /
resting phase ✔
3 idea that shape is (too), irregular /
asymmetrical (so cannot divide) ✔
Studies show that after damage by infection or injury, it is possible for nephron tissues to be
regenerated. Adult stem cells are involved in this process.
What features of adult stem cells make them suitable for regeneration of tissues in the kidney?
(adult stem cells) are multipotent ✔
(differentiate to) become any cell
type within, kidney / nephron (tissue)
✔
