White blood cells help to defend the body against pathogens.
.1
What are the molecules on the surface of a pathogen that white blood cells recognise as foreign?
[1 mark]
.2
Describe three ways white blood cells defend the body against pathogens.
[3 marks]
.3
A person has antibodies against the measles virus. These antibodies do not protect the person against the mumps virus.
Explain why.
[2 marks]
4 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
Scientists compared two ways of growing new bone cells to repair a damaged bone.
Method A uses adult stem cells from the patient's own bone marrow.
Method B uses stem cells from an embryo.
The table shows their results.
Table comparing method A (bone marrow stem cells) and method B (embryonic stem cells): cells after 14 days, 18 million and 45 million; percentage becoming bone cells, 85 and 55.
Measurement
Method A: bone marrow
Method B: embryo
Cells after 14 days (millions)
18
45
Cells that became bone cells (%)
85
55
.1
Compare the results of method A and method B.
[2 marks]
.2
Calculate how many bone cells method B produced. Give your answer in millions.
[1 mark]
.3
Suggest one advantage of method A for the patient that is not shown in the table.
[1 mark]
5 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
The body cells of a species of fish contain 30 chromosomes, in 15 pairs.
.1
Give the number of chromosomes in one of this fish's gametes.
[1 mark]
.2
Give the number of chromosomes in a fertilised egg cell of this fish.
[1 mark]
.3
Describe what happens to the chromosomes when a cell divides by meiosis to form gametes.
[3 marks]
4 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
Scientists studied the risk of lung cancer in adults who smoked different numbers of cigarettes each day. The graph shows how many times greater the risk was than for non-smokers.
051015202530510152025Cigarettes smoked per dayRisk compared with non-smokers1481522
.1
Describe the pattern shown in the graph.
[1 mark]
.2
Calculate how many times as great the risk is for a person smoking 20 cigarettes a day as for a person smoking 5 a day.
[1 mark]
.3
A correlation does not always mean that one factor causes another.
Explain what other evidence scientists needed before concluding that smoking causes lung cancer.
[2 marks]
6 marksFoundation and Higher
Spec and skills
Original practice question
Answer and supported method checks
Tobacco mosaic virus (TMV) infects tomato and tobacco plants. HIV infects humans.
.1
TMV causes a mosaic pattern of discoloured patches on the leaves.
Explain why an infected plant grows more slowly.
[3 marks]
.2
Explain how viruses make people ill.
[2 marks]
.3
How is HIV controlled in a person who is infected?
