Our body consists of many organs and each organ is formed from tissues that their building unit is the cell. Cells are the fundamental, structural, and functional units of every known living organism. Instructions needed to direct activities are contained within a DNA (deoxyribonucleic acid) sequence.
The human genome (the total composition of genetic material within a cell) is packaged into larger units known as chromosomes. Each chromosome is formed from many genes. Genes are the controller of the development and function of an organism as they contain the instructions of how to make protein. Mutations can lead to alterations in the structure of an encoded protein or to a reduction or complete loss in its expression. Since the change in the DNA sequence affects all copies of the encoded protein, mutations can be particularly harmful to a cell or organism.
Several diseases are caused or influenced by genetics. Genes, through the proteins they encode, regulate how efficiently foods and chemicals are metabolized, how effectively toxins are detoxified, and how vigorously infections are targeted. Genetic diseases can be categorized into three main groups: single-gene, chromosomal, and multifactorial.
Although some genetic changes may cause or modify disease risk, other changes may lead to no increased risk or a neutral presentation. For example, genetic variants in a single gene account for the different blood types: A, B, AB, and O.
Understanding the clinical significance of genetic variation is a complicated process because of our limited knowledge of which genes are involved in a disease or condition and the multiple gene-gene and gene-behavior-environment interactions likely to be involved in complex chronic diseases.
New technologies are enabling faster and more accurate detection of genetic variants in hundreds or thousands of genes in a single process.
Lodish H, Berk A, Zipursky SL, et al. Molecular Cell Biology. 4th edition. New York: W. H. Freeman; 2000. Section 8.1, Mutations: Types and Causes. Available from: https://www.ncbi.nlm.nih.gov/books/NBK21578/