ch. 14b- Mendelian inheritance

hybridization

interbreeding between two different varieties or species

true breeding

the physical appearance of the offspring in each successive generation is identical to the previous one

P₁ generation

the parental generation in a series of crosses

F₁ generation

the first filial, or offspring, generation of a particular mating

reciprocal cross

a cross in which the female and male parents are interchanged

dominant

describes an allele or trait that is expressed in heterozygotes

recessive

describes an allele or trait that is only expressed in homozygotes

F₂ generation

the second filial generation; the offspring from intercrossing among F₁ individuals

principle of segregation

half the gametes receive one allele of a gene and half receive the other allele

punnett square

a diagram used to predict the outcome of a genetic cross by showing all possible gametes of parents

testcross

any cross of an unknown genotype with a homozygous recessive genotype

incomplete dominance

inheritance in which the phenotype of the heterozygous genotype is intermediate between those of homozygous genotypes

codominance

a form of inheritance where both alleles in a heterozygous organism are fully expressed, resulting in a phenotype that shows both traits simultaneously.

probability

the likelihood of a specific outcome occurring in a genetic cross, often expressed as a fraction or percentage.

addition rule

applies when the possible outcomes being considered cannot occur simultaneously

multiplication rule

principle applies when outcomes can occur simultaneously, and the occurrence of one has no effect on the likelihood of the other

principle of independent assortment

states that segregation of one set of alleles of a gene pair different gene pair

epistasis

interaction between genes that modifies the phenotypic expression of genotypes

pedigree

a diagram of family history that summarizes the record of the ancestor—descendant relationships among individuals

incomplete penetrance

individuals with a genotype corresponding to a trait do not actually show the phenotype

variable expressivity

a particular phenotype is expressed with a different degree of severity in different individuals