Human Genetic Screening

Human Genetic Screening

Humans, like all other living organisms, have genes. These genes instruct our bodies to make proteins, these proteins are the molecules that determine the shape and function of each cell. Each gene or set of genes encode for the production of a particular protein.What is a gene ?The term " gene "was created by Wilhelm Johanssen, a Danish botanist in 1911. He was discussing units of inheritance that Mendel called factors.T.H. Morgan's studies on fruit fly genetics led to the idea of a gene as the smallest unit of recombination. Aggregated with this idea was another that said the gene was the unit of mutation, and another that the gene is the unit of function (the smallest unit of control over the phenotype ). Modern evidence suggests that recombination can occur between any two nucleotide, which make the unit of recombination only one nucleotide long . Some mutations change only one nucleotide, so the unit of mutation could be only one nucleotide long . The unit of function is the cistron which is about 900-1500 nucleotide long. So we can identify the gene as the length of DNA that codes for one functional product (6).

DNA of the human species carries more or less the same set of DNA with some variations . Variations in the DNA sequence can be neutral, others might have positive or negative influence. Genetic screening is testing of this variation (2).

Human race carries 3000-4000 diseases in it's genes, and it is important to distinguish between inherited diseases and infectious diseases. Inherited diseases are caused by mutated genes which are inherited by an individual from his or her parents (2). The faulty gene will be one of the many healthy thousands of genes we possess in our cells. To pinpoint the location of these faulty genes, scientists search for variations in larger piece of DNA called markers, these subunits lie nearby on the DNA chain, and form the basis of genetic screening.

What is genetic screening ?

The principle of genetic screening is based on the binding of a probe to the DNA molecule of the patient or the person to be screened. Complementary DNA nucleotide sequences bind to each other. The probe used is usually single stranded DNA, which binds to the test sample. The DNA sample can be analyzed by a technique called restriction fragment polymorphism (RFLP). In this technique the DNA sample is cut up with a mixture of restriction enzymes which cut the DNA at a specific sequences.