Genetics

Traits

Gregor Mendel

Genetic Principles

• Traits are passed from one generation to the next.

Genetic Principles

• The traits of an organism are controlled by genes.
• (Genes are segments of DNA on a chromosome.)

Genetic Principles

• Organisms inherit genes in pairs, one from each parent.

Genetic Principles

• Some alleles are DOMINANT and others are recessive.
• (Alleles are possible forms of a gene: tall/short; green/blue)

Genetic Principles

• DOMINANT alleles hide recessive alleles when both are inherited.

Genetic Principles

• Some alleles are neither dominant nor recessive but are codominant or have incomplete dominance.

Genetic Principles

• Phenotype - physical appearance
• Ex.: tall/short
• Ex. brown fur/black fur
• Ex. round/wrinkled

Genetic Principles

• Genotype - gene pair
• Ex.: TT, Tt, tt
• Ex. BB, Bb, bb
• Ex. RR, Rr, rr

Genotypes

• Dominant Allele: Use a capital letter to represent
• Recessive Allele: Use a lower case letter to represent
• Use the same letter for both
• Usually the first letter of the trait controlled by the dominant allele

Gender
XX (female)
XY (male)