Chromosomes are organized structures of DNA and proteins that are found in cells. A chromosome is a continuous piece of DNA, which contains many genes, regulatory elements and other material.
A gene is a locatable region of genomic sequence, corresponding to a unit of inheritance, which is associated with regulatory regions, transcribed regions and/or other functional sequence regions. The physical development and phenotype of organisms can be thought of as a product of genes interacting with each other and with the environment.
Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information. DNA is often compared to a set of blueprints or a recipe, since it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information.
An allele (pronounce a-leel) is one member of a pair or series of different forms of a gene. Usually alleles are coding sequences, but sometimes the term is used to refer to a non-coding sequence. An individual's genotype for that gene is the set of alleles it happens to possess.
A gene mutation is a permanent change in the DNA sequence that makes up a gene. Mutations range in size from a single DNA building block (DNA base) to a large segment of a chromosome. Gene mutations occur in two ways: they can be inherited from a parent or acquired during a person’s lifetime. Mutations that are passed from parent to child are called hereditary mutations. Mutation is generally accepted by the scientific community as the mechanism upon which natural selection acts, providing the advantageous new traits that survive and multiply in offspring or disadvantageous traits that die out with weaker organisms.
Both parents carry a normal gene (N), and a faulty, recessive, gene (n). The parents, although carriers, are unaffected by the faulty gene. Their offspring are affected, not affected, or are carriers.
One parent has a single, faulty dominant gene (D), which overpowers its normal counterpart (d), affecting that parent. When the affected parent mates with an unaffected and non-carrier mate (dd), the offspring are either affected or not affected, but they are not carriers.
Penetrance is a term used in genetics describing the proportion of individuals carrying a particular variation of a gene (an allele or genotype) that also express a particular trait (the phenotype). For example, known mutations in the gene responsible for Huntington disease have 95% penetrance, whereby 5% of those with the dominant allele for Huntington disease don't develop the disease and 95% do. In other word, penetrance is the percentage of individuals with a specific genotype that possess an associated phenotype.
Gene expression is the process by which inheritable information from a gene, such as the DNA sequence, is made into a functional gene product, such as protein or RNA. Gene regulation gives the cell control over structure and function, and is the basis for cellular differentiation, morphogenesis and the versatility and adaptability of any organism.
Modifier genes are genetic variants that affect the clinical manifestation of disease.
Gene Environment Interaction
Gene-environment interaction is a term used to describe any phenotypic effects that are due to interactions between the environment and genes. Naive nature versus nurture debates assume that variation in a given trait is primarily due to either genes, or the individual's experiences. The current scientific view is that neither genetics nor environment are solely responsible for producing individual variation, and that virtually all traits show gene-environment interaction.
A candidate gene is a gene, located in a chromosome region suspected of being involved in the expression of a trait such as a disease, whose protein product suggests that it could be the gene in question. A candidate gene can also be identified by association with the phenotype and by linkage analysis to a region of the genome.
Genome Wide Association Studies (GWAS)
A genome-wide association study is defined as any study of genetic variation across the entire human genome that is designed to identify genetic associations with observable traits (such as blood pressure or weight), or the presence or absence of a disease or condition. Whole genome information, when combined with clinical and other phenotype data, offers the potential for increased understanding of basic biological processes affecting human health, improvement in the prediction of disease and patient care, and ultimately the realization of the promise of personalized medicine. a genome-wide association study is defined as any study of genetic variation across the entire human genome that is designed to identify genetic associations with observable traits (such as blood pressure or weight), or the presence or absence of a disease or condition. Whole genome information, when combined with clinical and other phenotype data, offers the potential for increased understanding of basic biological processes affecting human health, improvement in the prediction of disease and patient care, and ultimately the realization of the promise of personalized medicine.
Stochastic is synonymous with "random." The word is of Greek origin and means "pertaining to chance”.
Statistics is a mathematical science pertaining to the collection, analysis, interpretation or explanation, and presentation of data. It is applicable to a wide variety of academic disciplines, from the natural and social sciences to the humanities, and to government and business.
Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues. The sequence of amino acids in a protein is defined by a gene and encoded in the genetic code.
Single Nucleotide Polymorphism, or SNP (pronounced "snip"), is a small genetic change, or variation, that can occur within a person's DNA sequence. The genetic code is specified by the four nucleotide "letters" A (adenine), C (cytosine), T (thymine), and G (guanine). SNP variation occurs when a single nucleotide, such as an A, replaces one of the other three nucleotide letters—C, G, or T.