THE MOLECULAR GENETICS DEPARTMENT
What is DNA?
DNA (deoxyribonucleic acid) contains the geneticcode instructing our body how to grow and function properly. It is a double-helix molecule organized in microscopic structures called chromosomes located in the nucleus of all our cells. Each DNA molecule is made of four nitrogenous bases: A (adenine), T (thymine), G (guanine), and C (cytosine) in various combinations. The order and the succession of these bases determine the body structure and function.
An important property of DNA is the ability to self-copy, resulting in identical copies; this function is vital because when a cell gets divided, every new cell has an identical copy of the DNA from the originalone. Human beings’ DNA is identical up to 99.9%. The uniqueness of each individual is determined by the 0.1% of DNA which is different.
What is a gene?
A gene is the basic structural and functional unit of heredity. Genes are made of DNAsequences and they are located onchromosomes, containing instructions for synthesising proteins and for regulating cell distinction. Each chromosome contains thousands of genes made of millions of base pairs. Any human being has two copies of each gene, one inherited from each parent. The genome (all the genes) determines the normal development of each individual.
What is a mutation?
When a cell divides, DNA is replicated, its division resulting in two identical cells, each bearing a complete set of genetic information. Sometimes, errors may occur during replication, changing the coding sequence. Such errors are called mutations. Mutations can be inheritedor acquired during the lifetime, and they can be passed on to the next generation.
Mutations occurring in an egg, sperm cell or immediately after fertilization are called de novo mutations. Most mutations do not alter the gene function and don’t have any impact on health and development. When a mutation alters the gene function, the resulting protein will be modified and its’ function altered, resulting in genetic disorders.
DNA analyses for inherited or acquired genetic diseases
What is a genetic disease?
A condition caused by changes in DNA is calleda genetic disease. The changes in DNA may cause pregnancy loss, neonatal death, severe chronic disease, or more mild disorders.
DNA analysis is mainly performed for individuals affected or suspected to carry genetic changes. All types of modifications can be analysed using different genetic testing techniques.
What are the recommendations for genetic testing?
Aneuploidy testing in prenatal diagnosis
Individuals affected by a genetic condition or with a family history of genetic disease
Parents of an affected child
Parents who are carriers for a certain gene
Positive immunological testing