Applied genetics" most impacts on society are as a result of genetic tests. In general, genetic tests seek to detect some feature of a person's genetic constitution. This feature can be a disease causing mutation or a marker DNA sequence used to detect presence of another gene. Obviously these procedures used for testing the status of DNA, RNA or chromosomes are included in genetic tests. What is more it is possible to include some protein based tests and classical medical examinations when they aim to detect inheritance of a trait. Genetic tests have been divided into four categories in this text, and they will be examined in greater detail later. These categories are: Prenatal tests that are applied on fetuses during pregnancy. Neonatal screening just after birth and career screening of marrying couples. Testing for serious late-onset disease before the symptoms occur. Testing to assess the probability of developing complex disease. There are a couple of considerations about genetic tests: .
1. First of all, the tests should be reliable. When a positive or a negative result is obtained, we should be confident in that result with a confidence approaching 100%. To achieve such a high accuracy is not as easy as it may at first appear to be. Meiotic recombinations that always occur take place during gamete generation, may separate a disease-associated gene and a marker DNA sequence which is used to detect mutated genes. False positive or negative results could be obtained. In addition, genetic tests look for the most common mutations that cause the disease. For example, a test would detect CFTR?F508 (Cystic Fibrosis Transmembrane Receptor) mutation, however it is not possible to detect infinite number of other mutations. Therefore, a genetic test can give such results so that the physician is convinced that his patient is normal while he is affected by an undetectable mutation. New tests are continuously being developed.