Punnett Squares

Punnett Squares

An allele of a gene is said to be dominant when it effectively overrules the other (recessive) allele

Dominant

An allele of a gene that is usually hidden by the dominant allele (requires 2 to be present)

Recessive

Terminology

2 different alleles of a gene

-EX: height --> T=tall
t=short
Tt=heterozygous dominant
(never tT)

Heterozygous

2 identical alleles of a gene

-Ex: height --> T=tall
t=short
TT= homozygous dominant
tt= homozygous recessive

Homozygous

Terminology

-description of the alleles





PHYSICAL

Phenotype

-genetic "code" for genes
-alleles expressed are dominant or recessive

GENETIC

Genotype

Terminology

​Monohybrid Punnett Square

-only one difference
- 2 x 2 (2 alleles from mom x 2 alleles from dad)
-percentage of each possible combination

Practice

In pea plants, purple flowers are dominant over white flowers, which are recessive. Cross two homozygous dominant (PP) parents.

Practice

In pea plants, yellow seeds are dominant and green seeds are recessive. Cross two heterozygous individuals (Yy).

​Practice

In pea plants, green pods are dominant over yellow pods. Cross a plant with yellow pods with a plant that is heterozygous for green pods.