MCDB 101B punnett square ratio memorization

9:3:3:1

Additive

• four distinct

9:3:4

Recessive Epistasis

• aa masks bb

9:7

Reciprocal Recessive Epistasis

• both genes required

12:3:1

Dominant Epistasis I

• Dominant A masks B_ and bb

13:3

Dominant Epistasis II

• Dominant A masks B (ex. inhibitory pathway)

15:1

Redundancy

• either gene is sufficient

3:1

Simple Dominance/Recessive

2:1

Recessive Lethal

1:1

Testcross