Mendelian & Non-Mendelian Genetics

allele

one form or version of a gene

genotype

the two alleles inherited for a particular gene; the genetic make up of a trait; the "genes"

phenotype

an individual's observable traits, such as height, eye color, and blood type; "Physical" traits

dominant

the allele in a genotype that masks the contribution of a second allele at the same locus on a chromosome

recessive

the allele in a genotype that is frequently masked by a second allele at the same locus on a chromosome

homozygous

description of a genotype of an individual who has two of the same allele, whether dominant or recessive

heterozygous

description of a genotype of an individual who has two different alleles, one dominant and the other recessive

Law of Segregation

the principle, originated by Gregor Mendel, stating that during the production of gametes the two copies of each hereditary factor separate so that offspring acquire one factor from each parent

Law of Independent Assortment

the principle, originated by Gregor Mendel, stating that when two or more characteristics are inherited, individual hereditary factors line up independently during gamete production, giving different traits an equal opportunity of occurring together

complete or simple dominance

type of dominance that occurs when an inherited trait is coded for by a single gene and that gene has two versions, or alleles: the dominant version and the recessive version, where the dominant version masks the recessive version

incomplete dominance

type of dominance that occurs when the phenotype of the heterozygous phenotype is distinct from and often intermediate to the phenotypes of the homozygous phenotypes

codominance

type of dominance that occurs when the contributions of both alleles are visible in the phenotype

multiple alleles

three or more alternative forms or versions of a gene

polygenic inheritance

type of inheritance that occurs when one characteristic is controlled by two or more genes; often there is a wide range of intermediate phenotypes

sex-linked traits

traits that are caused by genes that are found on the X and Y chromosomes

P generation

parent generation

F1 generation

first generation (offspring of the parent generation)

F2 generation

second generation (offspring of the F1 generation)

monohybrid cross

cross that follows just ONE trait

dihybrid cross

cross that follows TWO traits

test cross

involves the breeding of a phenotypically dominant individual (HH or Hh) with a phenotypically recessive individual (hh), in order to determine the genotype of the former by analyzing proportions of offspring phenotypes

pedigree

the recorded ancestry, especially upper-class ancestry, of a person or family

pure-bred or true-breeding

an individual with a homozygous genotype

hybrid

an individual with a heterozygous genotype

trait

a genetically determined characteristic

Gregor Mendel

an Austrian monk who discovered the basic principles of heredity through experiments in his garden

Punnett square

a diagram that is used to predict an outcome of a particular cross or breeding experiment

gene

a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring

Carrier

Heterozygote for a recessive genetic disorder

Epistasis

Phenotypic expression of a gene at one locus alters a gene at a 2nd locus

Pleiotrophy

a single gene that has multiple affects on the body such as sickle-cell anemia

Locus

location of a gene on a chromosome