Genetic screening can be used to identify people who have, are predisposed to, or are carriers of genetic diseases. Screening can be done at the phenotype level by identifying an abnormal protein such as an enzyme with altered activity. It can also be done at the genotype level by direct testing of DNA.
learning outcomes
You should be able to:
Compare and contrast phenotypic and genotypic genetic screening.
Explain how DNA testing is used for genetic screening.
What is the advantage of screening for genetic mutations by allele-
DNA analysis can be done on any tissue at any time in the life cycle of an individual. In addition, heterozygotes can be detected. Phenotype analysis by enzyme activity requires gene expression in an accessible tissue at a certain time and place. In many cases, heterozygotes cannot be detected.
Explain how allele-
A patient’s DNA could be tested to see if it hybridizes to sequences of the mutant β-globin gene. If it did, this would mean that the patient carries the mutation, and no further sequencing of the patient’s DNA would need to be done to verify this.
Ongoing research has resulted in the development of increasingly accurate diagnostic tests and a better understanding of various genetic diseases at the molecular level. This knowledge is now being applied to the development of new treatments for genetic diseases. In the next section we will survey various approaches to treatment, including modifications of the mutant phenotype and gene therapy, in which the normal version of a mutant gene is supplied.