Classical genetics

An allele is a variant of the sequence of nucleotides at a particular location, or locus, on a DNA molecule.

thumb|right|250px |The mollusc shell|shells of individuals within the [[bivalve mollusk species Donax variabilis show diverse coloration and patterning in their phenotypes.]] thumb|right |Here the relation between genotype and phenotype is illustrated, using a [[Punnett square, for the character of petal color in pea plants. The letters B and b represent genes for color, and the pictures show the resultant phenotypes. This shows how multiple genotypes (BB and Bb) may yield the same phenotype (purple petals).]]

A gamete ( ), reproductive cell, or sex cell, is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. The name gamete was introduced by the German cytologist Eduard Strasburger in 1878.

type of biological inheritance

thumb|upright|A haploid set that consists of a single complete set of chromosomes (equal to the monoploid set), as shown in the picture above, must belong to a diploid species. If a haploid set consists of two sets, it must be of a tetraploid (four sets) species.

set of all genes in a population

A haplotype is a group of alleles in an organism that are inherited together from a single parent, and a haplogroup (haploid from the , haploûs, "onefold, simple" and ) is a group of similar haplotypes that share a common ancestor with a single-nucleotide polymorphism mutation. More specifically, a haplotype is a combination of alleles at different chromosomal regions that are closely linked and 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. Such as t

principle that allele and genotype frequencies in a population will remain constant over generations in the absence of other evolutionary influences

thumb|This image shows haploid (single), diploid (double), triploid (triple), and tetraploid (quadruple) sets of chromosomes. Triploid and tetraploid chromosomes are examples of polyploidy.

thumb|350px|An example of epistasis is the interaction between hair colour and baldness. A gene for Alopecia totalis|total baldness would be epistatic to one for [[blond hair or red hair. The hair-colour genes are hypostatic to the baldness gene. The baldness phenotype supersedes genes for hair colour, and so the effects are non-additive.]] thumb|Example of epistasis in coat colour genetics: If no pigments can be produced the other coat colour genes have no effect on the phenotype, no matter if they are dominant or if the individual is homozygous. Here the genotype "c c" for no pigmentation is

thumb|300px|Time course imaging of two maize [[inbreds and their F1 hybrid (middle) exhibiting heterosis.]]

tendency of DNA sequences that are close together on a chromosome to be inherited together

thumb|363px|DNA molecule 1 differs from DNA molecule 2 at a single base-pair location (a C/A polymorphism). A haplotype (haploid genotype) is a group of alleles in an organism that are inherited together from a single parent.

220px|thumb|right|The American lobster#Coloration|blue lobster, an example of a mutant thumb|right|220px|Wild-type Physcomitrella patens|Physcomitrella and [[knockout mosses: Deviating phenotypes induced in gene-disruption library transformants. Physcomitrella wild-type and transformed plants were grown on minimal Knop medium to induce differentiation and development of gametophores. For each plant, an overview (upper row, scale bar corresponds to 1 mm) and a close-up (bottom row, scale bar equals 0.5 mm) is shown. A, Haploid wild-type moss plant completely covered with leafy gametophores and

phenotype of the typical form of a species as it occurs in nature. Most prevalent allele – i.e., the one with the highest gene frequency – is the one deemed as wild type

DNA locus associated with variation in a quantitative trait

specific feature of an organism

diagram used to predict the possible outcomes of a breeding experiment, and their respective likelihoods

A polygene is a member of a group of non-epistatic genes that interact additively to influence a phenotypic trait, thus contributing to multiple-gene inheritance (polygenic inheritance, multigenic inheritance, quantitative inheritance), a type of non-Mendelian inheritance, as opposed to single-gene inheritance, which is the core notion of Mendelian inheritance. The term "monozygous" is usually used to refer to a hypothetical gene as it is often difficult to distinguish the effect of an individual gene from the effects of other genes and the environment on a particular phenotype. Advances in st

thumb|300px|Homozygous and heterozygous Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism.

alt=Introgressive phylogenetic clade|thumb|A phylogenetic model of introgressive hybridization; the hybrid zone of the two species' lineages is shown in blue, with each horizontal line representing an individual introgressive event. Introgression, also known as introgressive hybridization, in genetics is the transfer of genetic material from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species. Introgression is a long-term process, even when artificial; it may take many hybrid generations before significant backcrossin

allele that cause the death of the organism that carries them

branch of genetics based solely on visible results of reproductive acts

first-generation hybrid (or crossbreed) animal or plant

mating between two organisms with different variations at one genetic chromosome of interest

interaction of a dominant allele with a recessive allele resulting in complete expression or non-expression of a trait

In medical genetics and other medical fields, a proband, propositus (male proband), or proposita (female proband) is a particular subject (human or other animal) being studied or reported on. On pedigrees, the proband is noted with a triangle (male) or circle (female) shaded accordingly. Denoting the proband is important, so the relationship to other individuals can be seen and patterns established.

obsolete theory in biology

concept in classical genetics

occurs when two strains of an organism with different homozygous recessive mutations that produce the same mutant phenotype produce offspring with the wild-type phenotype when mated or crossed

human ability to roll the tongue into a tube

Ratio of characters

selective removal of alleles that are deleterious

biological lab technique

some certain genres of inheritance that doesn't follow the rules of mendelian inheritance

thumb|440x440px|Synteny (in the modern sense) between human and mouse chromosomes. Colors in the human chromosomes indicate regions homologous with parts of the mouse chromosome of the same color. For instance, sequences homologous to mouse chromosome 1 are primarily on human chromosomes 1 and 2, but also 6, 8, and 18. The X chromosome is almost completely syntenic in both species. In genetics, the term synteny refers to two related concepts: In classical genetics, synteny describes the physical co-localization of genetic loci on the same chromosome within an individual or species. In geno

diagram showing the occurrence and appearance or phenotypes of a particular gene or organism, in generations

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Overdominance is a phenomenon in genetics where the phenotype of the heterozygote lies outside the phenotypical range of both homozygous parents. Overdominance can also be described as heterozygote advantage regulated by a single genomic locus, wherein heterozygous individuals have a higher fitness than homozygous individuals. However, not all cases of the heterozygote advantage are considered overdominance, as they may be regulated by multiple genomic regions. Overdominance has been hypothesized as an underlying cause for heterosis (increased fitness of hybrid offspring).

nonfunctional allele (a variant of a gene) caused by a genetic mutation

right|thumb|280px|Overview of paleopolyploidy process. Many higher eukaryotes were paleopolyploids at some point during their evolutionary history.

traits produced by genes located on the Y chromosome

link between a disease and the causal genetic entity

Sex-linked mutation

mutant mouse that eats excessively and becomes profoundly obese

identical nucleotide sequence due to inheritance without recombination from a common ancestor

breeding experiment in genetics

Concept in genetics