Classical (Mendelian) Genetics terms

Genetics

the study of heredity, the process by which characteristics are given from parents to their offspring through genes

character

a detectable, heritable feature of an organism, such as flower color, that varies among individuals

trait

variant of a character, such as purple or white flower color

true-breeding plants, pure-breeding plants

a variety of plants which — when self-pollinated (and subsequently self-fertilized) — give rise to identical offspring, generation after generation ( with respect to a specific trait

stamen

pollen-producing organ of a flower

Carpel

egg-bearing organ of a flower

stigma

the very tip of the carpel

self-pollination

the transfer of pollen from an anther of a flower on one plant to the stigma of the same flower or the flower on the same plant, subsequently self-fertilization may occur

cross-pollination

the transfer of pollen from an anther of a flower on one plant to the stigma of a flower on another plant, subsequently cross-pollination may occur

to mate, to cross

to bring two parental organisms together to produce offspring

hybridization

the mating (crossing) of true-breeding plants with contrasting traits

hybrids

the offspring of hybridization

P (F0) generation

parental generation

F1 generation

first filial generation (offspring of P generation)

F2 generation

second filial generation (offspring of F1 generation)

Reciprocal cross

the cross with switched parental gender

gene

factor of inheritance controlling a character (section of DNA which codes for a particular protein)

Alleles

different forms of the same gene

phenotype

appearance, the physical and physiological trait of an organism determined by its genetic makeup

genotype

the genetic makeup of an organism, given a pair of alleles, it determines a particular trait

homozygote

an individual that had two identical alleles for a given gene, they are also called homozygous

heterozygote

an individual that has two different alleles for a given gene, they are also called heterozygous

dominant / recessive phenotype

phenotype 1 is said to be dominant over phenotype 2, if the heterozygote shows phenotype 1, in this case phenotype 2 is recessive

dominant / recessive alleles

dominant alleles always appear in the phenotype, irrespective of whether the genotype is homozygous or heterozygous. recessive alleles appear in the phenotype only if the genotype is homozygous

punnet square

a diagram used in the study of inheritance to show the results of random fertilization in genetic crosses

test cross

breeding of an organism of unknown genotype with a homozygous recessive individual to determine the unknown genotype, the ratio of phenotypes in the offspring determines the unknown genotype

monohybrid

an organism that is heterozygous with respect to a single gene of interest, all of the offspring between parents (that are homozygous for different alleles) are called monohybrids

monohybrid cross

a cross between two heterozygous individuals

dihybrid

an organism that is heterozygous with respect to two genes of interest, all the offspring between parents doubly homozygous for different alleles are dihybrids

Mendel's law of uniformity

if one crosses two pure-breeding varieties that differ in one trait of one character, the filial generation shows only one trait

Mendel's law of segregation

1. if one crosses hybrids of F1 (or allows self-pollination within a member of F1) the parental traits occur again in a well-defined ratio in F2

2. the law states that two alleles separate from each other when gametes are produced, each gamete only gets one allele of each pair, when they define during fertilization, the offspring has two alleles - one from each parent

incomplete dominance

the situation in which the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele

codominance

the situation in which the phenotype of both alleles are exibited in the heterozygote