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Punnetts Cheat Sheet (DRAFT) by

Honors Biology - genetics and Punnett squares

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Monohybrid Cross

Terms

Homozygous Dominant - AA
Homozygous Recessive - aa
Hetero­zygous - Aa; sometimes called a "­car­rie­r"
Genotype - the alleles inherited from parents; repres­ented by letters (example: AA)
Phenotype - observable trait that results from the genotype (example: Brown Eyes)
Dominant - masks recessive trait; only need to inherit one copy to display trait
Recessive - must inherit two recessive alleles to display trait; "­hid­den­" when dominant allele is present

Males and Females

  

Dihybrid Cross

Use FOIL to determine each possible combin­ation that can be passed from parent to child.

Dihybrid FOIL

Incomplete Dominance

Polygenic Traits

When two or more genes control a trait
Skin Color - 4 to 7 genes
Eye Color
Height
Blood Type (Type + Rh Factor)
 

Codomi­nance

Codomi­nance (Blood Type)

A is Codominant with B
O is recessive to A and B
+ is dominant
- is recessive

X-Linked

* X-linked traits are much more common in males than females because males have only one X chromo­some. Females need to inherit two mutated alleles to have the disease, while men can get the disease with just one mutated allele.
* XC X is an unaffected female carrier
* XC Y is an affected male
* XC XC is an affected female