Biology 9700 · AS & A Level · Genetic technology applied to medicine
Genetic technology applied to medicine — practice question
Cancer is a condition in which the normal control of cell division is lost, so malignant tumours develop. For many types of cancer, early detection can lead to successful treatment.
The BRCA2 protein helps to suppress tumour development. The gene that codes for this protein is found on chromosome 13.
Several different dominant alleles of this gene, BRCA2, code for faulty forms of the protein. Having any one of these faulty alleles raises the likelihood of developing several types of cancer, including breast cancer. However, not all people with one of these alleles develop cancer, because environmental influences, including lifestyle, are also involved.
Fig. 5.1 is a pedigree (family tree) showing cancers across four generations of a family. A faulty BRCA2 allele was confirmed in person 15. The other individuals with cancer were not tested for the allele. Individuals 24-30 are all under twelve years old.
(a)[4]
Discuss the extent to which Fig. 5.1 provides evidence that a faulty BRCA2 allele increases the chance of a person developing cancer.
(b(i))[1]
Explain what the term genome means.
(b(ii))[1]
Suggest a type of cell taken from a blood sample that is suitable for checking whether this allele is present, and justify your choice.
(b)
People whose families are thought to have a faulty $BRCA2$ allele may choose to be tested for whether it is present in their own genome.
A company based in the USA sells a microarray containing DNA probes for 20 different alleles that are linked to an increased cancer risk, including the faulty $BRCA2$ alleles. This microarray can be used in a medical facility or research laboratory to test blood samples for the presence of these alleles.
(b(iii))[4]
Outline how a microarray allows particular alleles to be detected.
(b(iv))[2]
Suggest one benefit and one drawback of screening for faulty alleles of $BRCA2$ before any symptoms appear.
Worked solution & mark scheme
This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Individual 8 or 11 carries the BRCA2 allele but has no cancer” …