Syllabus Edition
First teaching 2023
First exams 2025
A scientist counted 24 chromosomes in each of the root cells of a melon plant.
What is the diploid and haploid number of chromosomes for this species?
|
haploid number |
diploid number |
|
|
A B C D |
24 12 48 24 |
12 24 24 48 |
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What is the role of a telomere?
to enable correct coiling of genetic material
to aid the division of genetic material
to prevent the loss of genetic material
to initiate the replication of genetic material
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When animal cells undergo mitosis, which structure organises spindle formation?
centrosome
nucleolus
centriole
centromere
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Which of the following processes involve mitosis?
growth, repair and semi-conservative replication
repair, growth and asexual reproduction
reduction division, asexual reproduction and growth
repair, reduction division and asexual reproduction
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Chromosomes in a nucleus are shown in the diagram below.
What are the structures R and S?
| R | S | |
|
A B C D |
centromere centromere chromatid chromatid |
chromatid centriole centromere centriole |
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Which statement about mitotic cell division is incorrect?
DNA is replicated semi-conservatively during mitosis
DNA is normally unchanged from one generation of cells to the next
the daughter cells have the potential to produce the same enzymes as the parent cell
the same quantity of DNA is distributed to the nuclei of two new cells
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In which of the processes shown in the table is mitosis required?
| genetic variation | increase in cell number | replacement of damaged cells | |
| A | x | ✓ | ✓ |
| B | ✓ | x | x |
| C | ✓ | ✓ | x |
| D | x | x | ✓ |
key
✓ contributes to process
x does not contribute to process
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What is the end result of mitosis?
one dead cell and one new cell
two genetically identical clones of the parent cell
two cells with half the amount of DNA as the parent cell
one parent cell and two daughter cells, all identical
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At what stage of the cell cycle would a cell be producing the most mRNA molecules?
mitosis
G1 phase
S phase
G2 phase
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Which statement does not describe a stem cell?
a cell that is required in the immune system
a cell only found in embryos
a cell that produces cells capable of differentiating
a cell that can divide an unlimited number of times
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Mitosis is required in which of the following processes?
1 only
2 only
1 and 2 only
1, 2 and 3
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What processes during mitosis ensure that the genetic constitution of the cell is maintained?
1, 2 and 3 only
1, 2 and 4 only
2, 3 and 4 only
1, 2, 3 and 4
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Tumors are formed from uncontrolled cell division of cancer cells.
Which statement describes the difference between a normal cell and a cancer cell?
only cancer cells have mutated DNA
cancer cells do not undergo cytokinesis
cancer cells have a shorter interphase
cancer cells do not have metaphase
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The cell cycle is shown in the diagram below.
If dividing cells, cells are supplied with radioactive nucleotides, at which point will the nucleotides be incorporated into the chromosomes?
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What properties does a human cell have just before it enters prophase?
| nuclear envelope present | spindle present |
number of chromatids |
number of molecules of DNA in nucleus | |
|
A B C D |
no yes yes yes |
yes no yes no |
46 92 46 92 |
46 92 92 46 |
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The statements below are about two genes involved in breast cancer.
Which genetic combination is most likely to result in breast cancer?
| gene | ||
| BRAC1 | p53 | |
| A | ✓ | ✓ |
| B | ✓ | X |
| C | X | ✓ |
| D | X | X |
Key:
✓ = normal active gene
x = mutated gene
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DNA replication is promoted by chromosome telomeres and are not completely replaced during mitosis.
However, substance X is known to completely replace telomeres during mitosis.
What will be the effect of growing a cell culture with and without substance X?
| with substance X | without substance X | |
| A |
cell division stops immediately |
cells continuously divide |
| B |
cells continuously divide |
cell division eventually slows and stops |
| C | cell division eventually slows and stops |
cell division stops immediately |
| D | cells divide quicker |
cells continuously divide |
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Radioactive thymine is supplied to mammalian skin cells in tissue culture.
At which stage in the cell cycle will the thymine be used in the nuclei?
interphase
metaphase
prophase
anaphase
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The risk of developing a cancerous tumour is increased by exposure to which of the following?
| ultraviolet light | viruses | carbon monoxide | X-rays | |
| A | ✓ | ✓ | x | ✓ |
| B | ✓ | x | ✓ | ✓ |
| C | x | ✓ | ✓ | x |
| D | ✓ | x | ✓ | x |
key
✓ increases risk
x does not increase risk
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Mice in laboratories had their p53 genes switched off. These mice went on to develop tumours.
When their p53 genes were switched on again, the tumour cells stopped dividing and died within a few days. Healthy cells in the mice were unaffected.
What do these observations suggest?
the p53 gene acts as a tumour suppressor gene
p53 protein causes all cells to die
the p53 gene encourages the growth of tumours
p53 protein speeds up the mitotic cell cycle the p53
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Which of the following requires only mitosis during their production?
root hairs
cancerous tissue
gametes
antibodies
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The diagram shows a cell of an organism after replication division.
What is the diploid number for this organism?
10
20
40
46
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Around 250 billion red blood cells and 20 billion white blood cells are replaced each day. Blood cells are generated from stem cells in the bone marrow.
What type of stem cells are found in human bone marrow?
pluripotent
totipotent
omnipotent
multipotent
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What is the composition of telomeres and why?
| composition | reason | |
| A | protein | it is able to protect the DNA |
| B | RNA | it is made of different nucleotides to DNA |
| C | C/G nucleotides only | forms a high number of hydrogen bonds |
| D | C/G/A/T nucleotides | because telomeres are like the coding regions |
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Why does DNA condense into tightly packed chromosomes?
easier to access genes
because it contains histone proteins
the volume of the cell is small
easier to separate the genetic material
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Cells divide in response to a signal called a growth factor. Growth factors are proteins that bind to receptors on the surfaces of cells.
At which point in the cell cycle will the growth factor bind?
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The DNA of cancer cells is mutated.
Which of the following proteins would not cause cancer if mutated?
DNA repair proteins
aquaporin channel proteins
cell death proteins
cell adhesion proteins
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If a 14 cm long piece of string was packed into a 7 cm long tube, the packing ratio would be 2. The packing ratio is a useful measure of the degree of compactness achieved.
The linker DNA between nucleosomes is 72 base pairs long. Each base pair occupies a 0.52 nm length of the DNA double helix. Nucleosomes plus their linker DNA form a 10 nm wide fibre.
What is the packing ratio of DNA in this form of chromatin?
0.052
37.44
3.7
13.8
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Which cells contain telomerase?
|
1 |
B-lymphocytes |
|
2 |
embryonic cells |
|
3 |
heart cells |
2 only
1 and 3 only
1 and 2 only
1,2 and 3
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