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23 Cards in this Set
- Front
- Back
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gene pool |
the set of all genes, or genetic information, in any population, usually of a particular species. |
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relative frequency |
the average number of occurrences of a particular event in a large number of repeated trials.
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single-gene trait |
A single-gene trait is a phenotypic trait controlled by two homologous alleles within one gene. |
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polygenic trait |
This means that each dominant allele "adds" to the expression of the next dominant allele. Usually, when there is wide variation in the trait. For example, humans can be many different sizes. Height is a this type of trait, controlled by at least three genes with six alleles. |
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directional selection |
a mode of natural selection in which a single phenotype is favored, causing the allele frequency to continuously shift in one direction. |
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stabilizing selection |
a type of natural selection in which genetic diversity decreases and the population mean stabilizes on a particular trait value. When the average phenotype is favored. |
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disruptive selection |
describes changes in population genetics in which extreme values for a trait are favored over intermediate values. In this case, the variance of the trait increases and the population is divided into two distinct groups. |
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genetic drift |
variation in the relative frequency of different genotypes in a small population, owing to the chance disappearance of particular genes as individuals die or do not reproduce. |
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founder effect |
the reduced genetic diversity that results when a population is descended from a small number of colonizing ancestors. |
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genetic equilibrium |
the condition of an allele or genotype in a gene pool (such as a population) where the frequency does not change from generation to generation. |
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speciation |
the formation of new and distinct species in the course of evolution. |
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reproductive isolation |
situation where different species may live in the same area, but properties of individuals prevent them from interbreeding. The things which stop species or groups of organisms reproducing sexually are called isolating mechanisms. |
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behavioral isolation |
An isolating mechanism in which two species do not mate because of differences in courtship behavior. |
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geographic isolation |
is a term that refers to a population of animals, plants, or other organisms that are separated from reproducing with other organisms of the same species because of barriers like rivers or mountains |
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temporal isolation |
an evolutionary mechanism that keeps individuals of different species from reproducing, even if they live in the same environment. the barrier is usually time related in some way. |
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genotype |
the genetic constitution of an individual organism. |
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phenotype |
the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment. |
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homozygous |
When an individual has two of the same allele, whether dominant or recessive. |
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heterozygous |
having one each of two different alleles. |
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dominant |
traits that are expressed or seen when a heterozygous genotype is present. Heterozygous just means having two different alleles for a gene. Recessive alleles are masked by these. |
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recessive |
a trait that gets masked by a dominant gene. For example, your mom's recessive gene for blue eyes was trumped by your dad's dominant gene for brown eyes. That's how you got stuck with brown eyes. |
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allele |
one of two or more alternative forms of a gene and are found at the same place on a chromosome. |
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gene |
the basic physical and functional unit of heredity. |
