The cilia on ciliated epithelial cells vary in length, both within one person and from one individual to another.
Samples of ciliated epithelial tissue were taken from the airways of healthy people, and the mean cilia length was found for each person.
The participants in the investigation were divided into two categories:
• people who had been exposed to a harmful environmental factor
• people who had not been exposed to a harmful environmental factor.
The findings are shown in Fig. 3.1.
(a(i))[1]
State the form of variation shown by the mean cilia length in each group of people in Fig. 3.1.
(a(ii))[2]
Suggest two harmful environmental factors that the people may have been exposed to, which might explain the difference between the two curves in Fig. 3.1.
(b(i))[4]
Using Fig. 3.2, explain how genes such as A, B and C can turn on other genes.
(b(ii))[5]
Describe how microarray analysis can be used to identify the genes switched on by the product of gene C.
(c)[3]
Suggest how knowledge of the genes for these receptor proteins could help in the treatment of asthma.
Worked solution & mark scheme
This 15-mark question has a full step-by-step worked solution and mark scheme. One marking point: “continuous variation” …