Lecture 4: Heredity
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Created by:
Molly_Bonham3 on February 13, 2012
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25 terms
Terms | Definitions |
|---|---|
 Segregation | Mendell: crossing one trait with another to see the hybrid generation |
| Units | (genes) occure in pairs and that offspring inherit one unit from each parent |
| recessive | describing a trait that isnt expressed in heterozygotes; also refers to the allele that governs the trait. for a recessive allele to be expressed an individual must have 2 copies |
| dominant | describing a trait governed by an allele in the presence of another allele (what trait shows) |
| Homozygous | having the same allele at the same locus on both members of a pair of chromosomes, - having two identical alleles for a trait |
| Heterozygous | having different alleles at the same locus on member on a pair of chromosomes, - term used to refer to an organism that has two different alleles for the same trait |
| Genotype | genetic makeup of an individual - can refer to an organisms entire geentic makeup or to the alleles of a particular locus |
| Phenotype | observable physical characteristics of an organism - the detectible expressions of genotypes - frequently influenced by environmental factors |
| Principal of independent assortment | the dist of one pair of alleles into gametes does not influence the distribution of another pair - genes controlling different traits are inherited independently |
| Random assortment | the chance distribution of chromosomes to daughter cells during meiosis - important source of genetic variation |
| codominance | expression of 2 alleles in heterozygotes |
| polygenic | traits that are influenced by genes at 2 or more loci - ex eyes, skin, hair |
| Plieotropy | the capacity of a single gene to influence severla phenotypic expressions |
| allele frequency | in a pop. the percentage of all the alleles at a locus accounted for by one specific allele |
| Microevolution | small changes occur within a species such as changes in allele frequencies |
| Macroevolution | changes produced only after many generations such as the appearance of a new species |
| gene flow | exchange of genes between populations |
| genetic drift | random factor - evolutionary changes or changes in allele frequencies that are produced by RANDOM facotrs in small pop. result of small pop. size |
| Founder effect | type of genetic drift in which allele frequencies are altered in small pops that are taken from, or are remnants of, larger populations - because of random factors (2 or more individuals initially carried this trait and reproduced) this recessive trait has stayed present in the population |
| Speciation | The process by which a new species evolves from a prior species, the most basic process in macroevolution. |
| Allopatric speciation | The formation of a new species as a result of an ancestral population's becoming isolated by a geographic barrier. |
| Adaptive Radiation | process by which a single species or small group of species evolves into several different forms that live in different ways; rapid growth in the diversity of a group of organisms |
| Stasis | no change in population |
| Cladogenesis | - 2 species that derive from 1 species Speciation through a branching mechanism whereby an ancestral population gives rise to two or more descendant populations. |
| Anagenesis | - 1 species that changes over time - punctuated equilibrium , A pattern of evolutionary change involving the transformation of an entire population, sometimes to a state different enough from the ancestral population to justify renaming it as a separate species; also called phyletic evolution. |
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