patterns of inheritance Flashcards
genetic makeup of an organism
genotype
visible characteristic of an organism
phenotype
a version of a gene
allele
not true-breeding; having different alleles at a particular gene locus on a pair of homologous chromosomes
heterozygous
true-breeding; having identical alleles at a particular gene locus on a pair of homologous chromosomes
homozygous
determined by a single gene
monogenic
involving two gene loci
dihybrid
where both alleles present in the genotype of a heterozygous individual contribute to the individual’s phenotype
codominance/ codominant
characteristic for which there are three or more alleles in the population’s gene pool
multiple alleles
gene present on (one of) the sex chromosome
sex-linked
gene loci present on the same autosome (non-sex chromosome) that are often inherited together
autosomal linkage
interaction of non-linked gene loci where one masks the expression of the other; from the greek, ephistanai, meaning ‘stoppage’
epistasis
statistical test designed to find out if the difference between observed and expected data is significant or due to chance
chi-squared test
variation that produces phenotypic variations where the quantitative traits vary by very small amounts between one group and the next
continuous variation
genetic variation producing discrete phenotypes- two or more non-overlapping categories
discontinuous variation
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
directional selection
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
founder effect
a sharp reduction in size of a population due to environmental catastrophes such as earthquakes, floods, disease or human activities such as habitat destruction, overhunting or genocide, which reduces genetic diversity; as the population expands it is less genetically diverse than before
genetic bottleneck
natural selection leading to constancy within a population; intermediate phenotypes are favoured and extreme phenotypes selected against; alleles for extreme phenotypes may be removed from the population; stabilising selection reduces genetic variation within the population
stabilising selection
members of a species living in the same place at the same time that can interbreed
population
formation of two different species from one original species, due to geographical isolation
allopatric 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
speciation
formation of two different species from one original species due to reproductive isolation while the populations inhabit the same geographical location
sympatric speciation
selective breeding of organisms; involves humans choosing the desired phenotypes and interbreeding those phenotypes individually; therefore selecting the phenotypes that contribute to the gene pool of the next generation of these organisms
artificial selection
