genetics and evolution

genotype

the genetic makeup responsible for a particular trait

phenotype

an organisms observable traits

gene

genetic material coding for a single gene

locus

the chromosomal location of a gene

allele

one varient of a gene

homologous chromosomes

chromosome that code for the same set of genes

homozygous

having two identical allele for a gene

heterozygous

having two different alleles for a gene

complete dominance

when a heterozygote has the phenotype of only 1 of the alleles

codominance

both inherited alleles are completely expressed

incomplete dominance

phenotypes of the progeny that are intermediates of the parental phenotypes

leakage

when a loss of function mutation doesn’t result in complete lack of a phenotype

penetrance

the percentage of organisms having a certain genotype expressing a certain phenotype

expressivity

a term describing the variation in phenotype among organisms with a given genotype

gene pool

the set of all alleles in a population

nondisjunction

failure of tetrads to separate during meiosis I or sister chromatids in meiosis II

law of segregation

separation of alleles into haploid gametes

law of independent assortment

genese assort independently to the progeny

linked genes

genes on the same chromosome won’t necessarily undergo independent assortment

• The closer, the greater the linkage

recombination

exchange of segments from homologous chromosomes during prophase I — genetic diversity

genetic drift

random change in allele frequencies in a population

• smaller populations more susceptible

hardy-weinberg principle

p + q = 1

p² + 2pq + q² = 1

fitness

the ability of an organism to pass on its alleles

natural selection

differential reproduction of an organism based upon its fitness in its environment

group selection

natural selection acting at the level of a group of organisms rather than a individual

species

group of organisms that are capable of interbreeding to produce fit offspring

polymorphism

the existence of multiple phenotypes within a population

adaptation

an inherited trait that confers greater fitness

specialization

an adaptation to a specific function or environment

inbreeding

increased likelihood of mating between organisms with similar genotypes (limits genetic diversity)

outbreeding

increased likelihood of mating between organisms with different genotypes (increase genetic diversity)

bottleneck

dramatic decrease in the size of a population making it susceptible to a genetic drift