Trait

A characteristic caused by genetics or the environment

Chromosomes

Long strands of DNA that contain thousands of

genes

Genes

Part of chromosome that controls a trait(30,000 in humans)

Allele

Different forms of genes

Recessive allele

Only see this trait if two are present

Dominant Allele

Always shows its trait

Hybrid

Has two different alleles for same trait

Purebred

Has two identical alleles for same trait

Probability

The likelihood that an event will occur

Punnett Square

A chart that shows all possible combinations of

alleles between two organisms

Phenotype

The visibly expressed trait (ie. blue eyes)

Genotype

The allele combination for a trait (ie. Bb or bb.)

Homozygous

Two identical alleles (Purebred)

Heterozygous

Two different alleles (Hybrid)

Codominant Alleles

Neither allele is dominant(ie. Blood types or

spotted dog)

Incomplete Dominance

The dominant alleles mix – (Green flower

from blue and yellow alleles)

Meiosis

Process that creates sex cells with one copy of each gene or half the number of chromosome

Cross-Fertilization

A gamete(sex cell) from each parent gives one

allele for each trait to make a new organism(humans)

# of human chromosomes

23 pairs or 46 chromosomes

X and Y

Human chromosomes that determine gender

Mutation

When a chromosome is not copied correctly

Carrier

Someone who has one recessive allele for a trait but doesn’t

show it.

Pedigree

A chart that tracts a particular trait in a family

Karyotype

A picture of all the chromosomes of a cell

Genome

All the DNA in one cell of an organism

Genotype