definitions Flashcards
epistasis
interaction of non-linked gene loci where one masks the expression of the other
dominant epistasis
A dominant allele at one gene locus masks the expression of alleles at a second gene locus
recessive epistasis
two recessive alleles at one gene locus, will mask the expression of alleles at a second gene locus
complimentary epistasis
The presence of a particular allele at each locus is required for the expression of a particular phenotype
continuous variation
variation that produces phenotypic variation where the quantitative traits vary by very small amounts between one group and the next
-can change gradually and have a range of values
discontinuous variation
genetic variation producing discrete phenotypes- 2 or more non-overlapping categories
directional selection
A type of natural selection that occurs when an environmental change favours a new phenotype and so results in a change in the population mean
stabilising selection
-natural selection, leading to constancy within a population
-Intermediate phenotypes are favoured and extreme phenotype selected against
-Alleles for extreme phenotypes may be removed from the population
-stabilising selection reduces genetic variation within the population
founder effect
-when a small sample of an original population establishes in a new area
-its gene pool is not as diverse as that of the parent population
genetic bottleneck
-A sharp reduction in size of a population due to environmental catastrophes, such as earthquakes, flood, disease, or human activities, such as habitat destruction, over hunting or genocide, which reduces genetic diversity
-as the population expands it is less genetically diverse than before
population
members of a species living in the same place, and at the same time that can interbreed
allopatric speciation
formation of two different species from one original species due to geographical isolation
sympatric speciation
formation of two different species from one original species due to reproductive isolation, while the population inhabit the same geographical location
speciation
The splitting of a genetically similar population into two or more populations that undergo genetic differentiation and eventually reproductive isolation, leading to the evolution of two or more new species
artificial selection
selective breeding of organisms
-involves humans, choosing the desired phenotypes and interbreeding those phenotypes individually, therefore, selecting the genotypes that contribute to the gene pool of the next generation of these organisms
