Topic 8 - Genetics Vocabulary #1-34

character

A structure or attribute determined by a gene or group of genes

trait

A variation of a particular character

true breeding

describes organisms homozygous for a specific trait and thus always produce offspring that have the same phenotype for that trait

hybridization

In genetics, the mating, or crossing, of two true-breeding varieties.

P generation

The parent individuals from which offspring are derived in studies of inheritance.

F1 generation

the first generation of offspring obtained from an experimental cross of two organisms

F2 generation

the offspring from crosses among individuals of the F1 generation

alleles

is one of a number of alternative forms of the same gene or same genetic locus (group of genes)

dominant allele

An allele that determines the phenotype of an individual organism when two different copies are present.

recessive allele

An allele that will not determine the phenotype unless the genotype is homozygous in that allele

law of segregation

first law of heredity stating that pairs of alleles for a trait separate when gametes are formed

Punnett square

a chart that shows all the possible combinations of alleles that can result from a genetic cross

homozygous

having two IDENTICAL alleles for a particular gene

heterozygous

having two DIFFERENT alleles for a particular gene

phenotype

The physical traits that appear in an individual as a result of its genetic make up.

genotype

the genetic makeup of an organism

testcross

the crossing of an individual of unknown genotype with a homozygous recessive individual to determine the unknown genotype

monohybrid

an organism that is heterozygous with respect to a single gene of interest

monohybrid cross

a cross between two organisms that are both heterozygous for one character of interest

dihybrid

an organism that is heterozygous with respect to two genes of interest

dihybrid cross

A cross between two organisms that are each heterozygous for two characters of interest

law of independent assortment

second law of heredity, stating that allele pairs separate from one another independently during gamete formation

probability

the likelihood that a particular event will occur

multiplication rule

the probability that two or more independent events will occur together is the product of their individual probabilities

addition rule

the probability that two or more mutually exclusive events will occur is calculated by adding together their individual probabilities

complete dominance

A type of inheritance in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable

incomplete dominance

A type of inheritance in which the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele

codominance

inheritance pattern in which a heterozygote expresses the distinct traits of both alleles

multiple alleles

the existence of more than two versions of the gene for a genetic character

quantitative character

A heritable feature in a population that varies continuously as a result of environmental influences and the additive effect of two or more genes

polygenic inheritance

An additive effect of two or more genes on a single phenotypic character

multifactorial character

phenotypic character that is influenced by multiple genes and environmental factors

pedigree

A diagram that shows the occurrence of a genetic trait in several generations of a family

carrier

individual who has one copy of the allele for a recessive disorder and does not exhibit symptoms