Module #8 Study Guide

Gregor Mendel
Founder of modern genetics.
True Breeding
If an organism has a certain characteristic that is always passed on to its offspring, we say this organism bred true with respect to that characteristic.
Self-pollination
a plant sexually reproducing with itself.
Allele
One pair of genes that occupies the same position on homologous chromosomes.
Genotype
Two-letter set that represents the alleles an organism possesses for a certain trait
Phenotype
The observeable expression of an organism’s genes.
Homozygous genotype
A genotype in which both alleles are identical
Hetrozygous genotype
A genotype with two different alleles
Dominant allele
An allele that will determine phenotype if just one is present in the genotype
Recessive allele
An allele that will not determine the phenotype unless the genotype is homozygous in that allele
Mendel’s Principles
1. The traits of an organism are determined by its genes
2. Each organism has two alleles that make up the genotype for a given trait
3. In sexual reproduction, each parents contributes ONLY ONE of its alleles to its offspring.
4. In each genotyp, there is a dominant allele. If it exists in an organism, the phenotype is determined by that allele.
Punnett Squares
Used to predict the likelihood that an offspring will have a given genotype and phenotype.
Pedigree
A diagram that follows a particular phenotype through several generations.
Monoybrid 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
Polygenetic inheritance
traits are caused by the interaction of several genes
Incomplete dominance
traits that are controlled by alleles
Epistasis
One set of allels might affect how another set of alleles is expressed
Pleiotrophy
A single gene affects multiple observable traits
Antigen
A protein that, when introduced in the blood, triggers the production of an antibody
Autosomal Inheritane
Inheriitance 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 the sex chromosomes
Mutation
A radical chemical change inn 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