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anthropology 300
chapter 4
| Term | Definition |
|---|---|
| Principle of Segregation | Genes (alleles) occur in pairs (because chromosomes occur in pairs). During gamete production, the members of each gene pair separate, so that each gamete contains one member of each pair. |
| Genotype | The genetic makeup of an individual; the actual alleles that are present |
| Phenotype | The observable, measurable, physical expression of the genotype as affected by the environment |
| Heterozygous | Having 2 different alleles at a given locus on a pair of homologous chromosomes |
| Homozygous | Having 2 of the same alleles at a given locus on a pair of homologous chromosomes |
| Dominant | An allele that masks the effect of another |
| Recessive | An allele whose expression can be masked by another |
| Codominant | The expression of two alleles in heterozygotes. Because neither allele is dominant or recessive, both influence the phenotype |
| Principle of Independent Assortment | The distribution of one pair of alleles into gametes does not influence the distribution of another pair. The gene controlling different traits are inherited independently of one another. |
| Mendelian or monogenic traits | Traits that are influenced by alleles at only one locus |
| Discrete distribution | Mendelian or monogenic traits, coded for by one gene, fall into clearly defined categories. For example, each human has either type A, B, AB or O blood. |
| Polygenic traits | Traits that are influenced by genes at two or more loci. |
| Continuous distribution | Polygenic traits, coded for by two or more genes, show continuous variation, from one extreme to another. Traits are measured in units on a scale with even increments (ex feet, in.), and every person falls somewhere on the continuum for that trait. |
| Species | A group of organisms that can interbreed and produce fertile offspring; a reproductively isolated group of organisms. |
| Population | Within a species, an interbreeding group of individuals; the group among which an organism is most likely to find a mate; a group of organisms sharing a gene pool. |
| Gene pool | The total complement or store of genes in a population; described by allele frequency. |
| Allele frequency | Proportion (expressed as percentage) of different alleles in the gene pool of a population. In a population, the percentage of all the alleles at a locus accounted for by one specific allele. |
| Evolution | A change in the allele frequency in the gene pool of a population through time |
| Microevolution | Small-scale changes in allele frequencies that can take place from generation to generation within a species. |
| Macroevolution | Large-scale evolutionary changes taking many generations that lead to speciation, the development of a new species |
| Genetic Drift | A change in allele frequency of a population due to chance or random factors (sampling errors) in small populations. |
| Founder effect | A type of genetic drift in which allele frequencies are altered in small populations that are taken from, or are remnants of, larger populations |
| Gene flow | A change in allele frequency of a population due to movement of alleles into or out of populations. The exchange of genes between populations. |
| Mutation | A change in allele frequency of a population due to a random alteration in genetic material in the gametes, resulting in an offspring with new phenotypic variation that can then be acted upon by natural selection. |
| Natural selection | A change in allele frequency of a population due to differences in reproductive success between individuals. |
| Balanced Polymorphism | Maintenance of two or more alleles in the population due to the selective advantage of the heterozygote. (Example Sickle Cell Anemia) |
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bonnie_cp
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