History, Gene Expression
A gene is the basic structural unit of inheritance in biological organisms. It is made up of a short segment of DNA and contains the necessary information to produce a specific protein. Each gene is separated from each other by non-coding sequences that serve other functions. Genes are strung together and tightly packed into structures called chromosomes. All the genes in an organism are located on chromosomes in the nucleus of most cells and represent the blueprint for instructions that make up an organism. For example, genes can determine physical characteristics in humans such as height, eye color, skin color, or any other trait. Genes are passed from one generation to the next through sex cells (the egg and the sperm) called gametes. Maternal and paternal genes combine at fertilization and each contribute to the observable features of the offspring, explaining why children often look like one or both parents.
Mutations, which are changes in the structure or sequence of DNA, can cause disease if it involves disruption in the specific sequence of a gene. For example, if a mutation disrupts a gene that encodes a protein responsible for controlling cell division, this loss of function might cause the cell and the cells that arise from it to continuously divide, producing cancer.