Pea In Your Genes

Gregor Mendel

• Liked to play with pea• Noticed that

certain Characteristics (inheritable physical features) showed up or disappeared in peas.

plants.

Characteristics

• Inheritable physical features – such as yellow peas or wrinkled peas.• Come from Genes – Which come from your

parents.• Also called Traits – could be pea color or

pea shape.

• A single trait can be expressed (shown) in different ways.• Allele is the different

representation of the same trait. Ex. Seed color: Yellow or Green• Yellow is one Allele for

Seed Color• Green is another Allele

Genotype & Phenotype

• Genotype – “code” for a trait• Phenotype – what you actually see. • Yellow peas – Use Y to represent Yellow• Green peas – Use y to represent Green

Yellow and Green Peas

Genotype Phenotype• YY – Yellow• Yy – Yellow• yy - Green

Three different Genotypes but Two Colors. Why?

• YY – Yellow• Yy – Yellow• yy - Green

• Dominant Allele – rep. by a capital letter – Y• Recessive Allele –

rep. by a lowercase letter - yDominant Alleles OVER POWER

Recessive Alleles

• YY – Homozygous Yellow• Yy – Heterozygous

Yellow• yy – Homozygous

Green

How do alleles pass from parent to child?

• Punnett Squares• What if you cross a

Homozygous Yellow Pea (YY) with a Homozygous Green Pea (yy)?

YYYYY

Y

y yyy

yy

100% Heterozygous Yellow Peas

YY

YYYY

y

y yyyy

25% Homozygous Yellow50% Heterozygous Yellow25% Homozygous Green