| Term | Definition |
|---|
| chromosome ("coloured body") | the visible bodies within dividing cells that contain DNA and thus carry the genetic information. |
| chromatid | a subunit of a chromosome, which contains one DNA molecule. |
| chromosome disjunction | separation of members of homologous chromosomes during meiosis. |
| gene | a segment of the DNA molecule that codes for a certain character. |
| locus | the location of a certain gene on the choromosome. |
| allele | a variant of the same gene. |
| monohybrid cross | crosses between genotypes with one locus that are heterozygous. |
| dihybrid cross | crosses between genotypes with two loci that are both heterozygous. |
| test-cross | cross between a homozygous recessive and an unknown genotype. |
| back-cross | cross between an offspring (usually the F1) genotype and one of the parental genotypes. |
| gene pool | the set of all alleles at all loci carried by individuals in a population. |
| genotypic frequency | the proportion of a given genotype within a population. |
| allele frequency | the proportion of a certain allele at a given locus within a population. |
| mutation | random change in the genetic code. |
| genetic drift | random changes in allele frequencies in a population from generation to generation. |
| migration(=gene flow) | movement of genes beween populations. |
| inbreeding | mating between relatives |
| inbreeding depression | loss or decrease of vigor, survivorship, and/or fecundity due to inbreeding. |
| selection | differential reproduction among differing phenotypes in a population. |
| heritability | proprotion og phenotypic variation that has a genetic basis. |
| selection differential | the difference between the mean of the group selected for reproduction and the mean of the entire population. |
| cline | gradual changes in the phenotype along an environmental gradient. |
| race | group of populations with similar allele frequencies that are different form those of other populations. |
| evolution | changes in allele frequencies within a population. |
| allopatric speciation | species formation from a common ancestor in geograpghically separate locations. |
| sympatric speciation | species formation from a common ancestor in the same geographical location |
| industrial melanism | increase in the frequency of the dark phenotype due to industrial pollution. |
| reproductive isolating barriers | genetically determined (thus heritable) mechanisms preventing gene flow between populations. |
| polyploidy | the state of having more than two sets of chromosomes. |
| adaptive differentiation | development of different phenotypes from a common ancestor due to adaptations to different environments. |
| adaptive radiation | development of several new species from a common ancestor due to adaptations to different environments. |
| paralell evolution | similar changes in the phenotype between two geographically isolated taxa (species, genera, etc.) |
| divergent evolution | accumulation of phenotypic differences between two lineages originating from a common ancestor over time. |
| convergent evolution | development of phenotypic similarities between distantly related taxa over time. |
| phyletic evolution (=anagenesis) | gradual changes in the phenotype without speciation events (splitting or branching) over time. |
| punctuated equilibrium | sudden development of new phenotypes that stay the same over long period of time. |
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