Genetics (Gregor Mendel)

Gregor Mendel

Father of genetics; studies inheritance transmission of physical traits across generations in pea plants

Genes

heritable units of information that determine or influence observable or measurable traits

Alleles

different molecular forms of a gene

Diploid cells

have pairs of homologous chromosomes of two copies of every gene locus

Haploid cells

have only one copy of each type of chromosomes

Genotype

set of alleles for any one gene that an individual organism has (AA, Aa, aa)

Homozygous

individual with two identitcal alleles of a gene (AA, aa)

Heterozygous

individual with nonidentical alleles of a gene (Aa)

Phenotype

refers to an organism's observable traits (determined by genotype)

Genetic cross

mating of two sexually reproducing individuals

Hybrid

the heterozygote offspring of a cross between two individuals that breed true for different forms of a trait

True breeding

term used to describe organisms that produce offspring identical to themselves if allowed to self-pollinate

P1

parental generation

F1

first filial generation

F2

second filial generation

monohybrid cross

a genetic cross involving one trait

Dihybrid cross

genetic cross involving two traits

Law of Independent Assortment

how alleles are sorted for one gene has no effect on other genes

Law of Dominance

For a pair of unit factors for a single trait, one unit factor is dominant and the other is recessive

Law of Segregation

This is the process by which paired alleles

separate into different gametes during meiosis.

True

True or False: individually both dominant traits show an F2 phenotypic ratio of 3:1. The inheritance of one trait does not affect inheritance of the other

Simple discrete traits

only two phenotypes for each; complete dominance relationships (that pea is either round or wrinkled)

Codominance

two nonidentical alleles of a gene are both fully expressed in heterozygotes, so neither dominant or recessive

Genotype: AA or AO

Phenotype: A

Genotype: AB

Phenotype: AB

Genotype: BB or BO

Phenotype: B

Genotype: OO

Phenotype: O

Incomplete dominance

one allele is not fully dominant over its partner

Epistasis

two or more gene products influence a trait; typically one gene product suppresses the effect of another

Polygenic

when multiple genes influence a trait

Continuous variation

when continuous phenotypes are divided into measureable categories and plotted as a bar chart, they form a bell-shaped curve

Pleiotropy

a single gene influences a variety of different traits

Genome

the complete set of an organism's genetic instructions containing all the information needed to build, function, and reproduce that organism, organized into chromosomes within cells