Apologia Biology 2nd edition Module 8

true breeding

if an organism has a certain characteristic that is always passed on to its offspring, we say that this organism bred true with respect to that characteristic

allele

one of a pair of genes that occupies the same position on homologous chromosomes

genotype

a two-letter set that represents the alleles an organism possesses for a certain trait

phenotype

the observable expression of an organism's genes

homozygous genotype

a genotype in which both alleles are identical

heterozygous genotype

a genotype with two different alleles

dominant allele

an allele that will determine the phenotype if just one is present in the genotype

recessive allele

an allele that will not determine the phenotype unless the genotype is homozygous

Mendel's principal #1 of genetics

The traits of an organism are determined by its genes.

Mendel's principal #2 of genetics

each organism has two alleles that make up the genotype for a given trait

Mendel's principal #3 of genetics

in sexual reproduction, each parent contributes ONLY ONE of its alleles to the offspring

Mendel's principal #4 of genetics

In each genotype, there is a dominant allele. If it exists in an organism, the phenotype is determined by that allele.

Pedigree

a diagram that follows a particular phenotype through several generations

monohybrid cross

a cross between two individuals, concentrating on only one definable trait

Dihybrid cross

a cross between two individuals, concentrating on two definable traits

autosomes

chromosomes that do not determine the sex of an individual

sex chromosomes

chromosomes that determine the sex of an individual

antigen

a protein that, when introduced in the blood, triggers the production of an antibody

autosomal inheritance

inheritance of a genetic trait not on a sex chromosome

genetic disease carrier

a person who is heterozygous in a recessive genetic disorder

sex-linked inheritance

inheritance of a genetic trait located on a sex chromosome

mutation

a radical chemical change in one or more alleles

change in chromosome structure

a situation in which a chromosome loses or gains genes during meiosis

change in chromosome number

a situation in which abnormal cellular events in meiosis lead to either none of a particular chromosome in the gamete or more than one chromosome in the gamete