Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms.
The genotype is the part of the genetic makeup of a cell, and therefore of any individual, which determines one of its characteristics (phenotype). The term was coined by the Danish botanist, plant physiologist and geneticist Wilhelm Johannsen in 1903.
Microevolution is the change in allele frequencies that occurs over time within a population. This change is due to four different processes: mutation, selection, gene flow and genetic drift. This change happens over a relatively short amount of time compared to the changes termed macroevolution which is where greater differences in the population occur.
Dominance in genetics is a relationship between alleles of one gene, in which the effect on phenotype of one allele masks the contribution of a second allele at the same locus. The first allele is dominant and the second allele is recessive. For genes on an autosome, the alleles and their associated traits are autosomal dominant or autosomal recessive. Dominance is a key concept in Mendelian inheritance and classical genetics. Often the dominant allele codes for a functional protein whereas the recessive allele does not.
A gene family is a set of several similar genes, formed by duplication of a single original gene, and generally with similar biochemical functions. One such family are the genes for human hemoglobin subunits; the ten genes are in two clusters on different chromosomes, called the α-globin and β-globin loci. These two gene clusters are thought to have arisen as a result of a precursor gene being duplicated approximately 500 million years ago.
A haplotype is a group of alleles in an organism that are inherited together from a single parent. However, there are other uses of this term. First, it is used to mean a collection of specific alleles in a cluster of tightly linked genes on a chromosome that are likely to be inherited together—that is, they are likely to be conserved as a sequence that survives the descent of many generations of reproduction. A second use is to mean a set of linked single-nucleotide polymorphism (SNP) alleles that tend to always occur together. It is thought that identifying these statistical associations and few alleles of a specific haplotype sequence can facilitate identifying all other such polymorphic sites that are nearby on the chromosome. Such information is critical for investigating the genetics of common diseases; which in fact have been investigated in humans by the International HapMap Project. Thirdly, many human genetic testing companies use the term in a third way: to refer to an individual collection of specific mutations within a given genetic segment;.
A variable number tandem repeat is a location in a genome where a short nucleotide sequence is organized as a tandem repeat. These can be found on many chromosomes, and often show variations in length among individuals. Each variant acts as an inherited allele, allowing them to be used for personal or parental identification. Their analysis is useful in genetics and biology research, forensics, and DNA fingerprinting.
The evolution of sexual reproduction describes how sexually reproducing animals, plants, fungi and protists could have evolved from a common ancestor that was a single celled eukaryotic species. There are a few species which have secondarily lost the ability to reproduce sexually, such as Bdelloidea, and some plants and animals that routinely reproduce asexually without entirely losing sex. The evolution of sex contains two related, yet distinct, themes: its origin and its maintenance.
A haplotype is a group of alleles in an organism that are inherited together from a single parent, and a haplogroup is a group of similar haplotypes that share a common ancestor with a single-nucleotide polymorphism mutation. More specifically, a haplogroup is a combination of alleles at different chromosomes regions that are closely linked and that tend to be inherited together. As a haplogroup consists of similar haplotypes, it is usually possible to predict a haplogroup from haplotypes. Haplogroups pertain to a single line of descent. As such, membership of a haplogroup, by any individual, relies on a relatively small proportion of the genetic material possessed by that individual.
RecLOH is a term in genetics that is an abbreviation for "Recombinant Loss of Heterozygosity".
Genetics is the study of heredity and variations. Heredity and variations are controlled by genes—what they are, what they do, and how they work. Genes inside the nucleus of a cell are strung together in such a way that the sequence carries information: that information determines how living organisms inherit various features. For example, offspring produced by sexual reproduction usually look similar to each of their parents because they have inherited some of each of their parents' genes. Genetics identifies which features are inherited, and explains how these features pass from generation to generation. In addition to inheritance, genetics studies how genes are turned on and off to control what substances are made in a cell—gene expression; and how a cell divides—mitosis or meiosis.
This glossary of genetics is a list of definitions of terms and concepts commonly used in the study of genetics and related disciplines in biology, including molecular biology and evolutionary biology. It is intended as introductory material for novices; for more specific and technical detail, see the article corresponding to each term.
SNP genotyping is the measurement of genetic variations of single nucleotide polymorphisms (SNPs) between members of a species. It is a form of genotyping, which is the measurement of more general genetic variation. SNPs are one of the most common types of genetic variation. A SNP is a single base pair mutation at a specific locus, usually consisting of two alleles. SNPs are found to be involved in the etiology of many human diseases and are becoming of particular interest in pharmacogenetics. Because SNPs are conserved during evolution, they have been proposed as markers for use in quantitative trait loci (QTL) analysis and in association studies in place of microsatellites. The use of SNPs is being extended in the HapMap project, which aims to provide the minimal set of SNPs needed to genotype the human genome. SNPs can also provide a genetic fingerprint for use in identity testing. The increase of interest in SNPs has been reflected by the furious development of a diverse range of SNP genotyping methods.
The Sex-linked (SL) Clearbody budgerigar mutation is one of approximately 30 mutations affecting the colour of budgerigars. It is the underlying mutation of the Texas Clearbody variety.
Zygosity is the degree of similarity of the alleles for a trait in an organism.
Disease gene identification is a process by which scientists identify the mutant genotypes responsible for an inherited genetic disorder. Mutations in these genes can include single nucleotide substitutions, single nucleotide additions/deletions, deletion of the entire gene, and other genetic abnormalities.
Quantitative trait loci mapping or QTL mapping is the process of identifying genomic regions that potentially contain genes responsible for important economic, health or environmental characters. Mapping QTLs is an important activity that plant breeders and geneticists routinely use to associate potential causal genes with phenotypes of interest. Family-based QTL mapping is a variant of QTL mapping where multiple-families are used.
