A2 3.5 Unit 5: 3.5.7 Gene expression is controlled by a number of features

Regulation of transcription and translation
Candidates should be able to:

• interpret information relating to the use of oncogenes and tumour suppressor genes in the prevention, treatment and cure of cancer
• evaluate the effect on diagnosis and treatment of disorders caused by hereditary mutations and those caused by acquired mutations

A2 3.5 Unit 5: 3.5.8 Gene cloning technologies allow study and alteration of gene function in order to better understand organism function and to design new industrial and medical processes

Medical diagnosis
The use of labelled DNA probes and DNA hybridisation to locate specific genes. Once located, the base sequence of a gene can be determined by

• restriction mapping
• DNA sequencing

Many human diseases result from mutated genes or from genes that are useful in one context but not in another, e.g. sickle cell anaemia.
DNA sequencing and the PCR are used to produce DNA probes that can be used to screen patients for clinically important genes.
The use of this information in genetic counselling, e.g., for parents who are both carriers of defective genes and, in the case of oncogenes, in deciding the best course of treatment for cancers.