How to create a punnett square.

Why is gene expression a regulated process?

A brief overview on Punnett Squares

  • Punnett square- a chart which shows/predicta all possible gene combinations in a cross of parents(whose genes are known).

  • The Punnett squares were named for the geneticist, Reginald Punnett.

  • He discovered basic principles of sex linkage and sex determination

  • Worked with the feather color traits of chickens to separate male and female

  • Gregor Mendel did this with pea plants for their heights


Step 1:

sign letters to represent genes/traits. Big letters represent dominant traits, small letters represent recessive traits. Ex:(B:dominant), (b:recessive).


Step 2:

Write down the genotypes of each parent. (given to you/ possible to determine)

BB*bb


Step 3:

List the gene the parents will pass on. for example for this case:



BB will give dominant traits


Bb will give dominant

Step 4:

Draw a punnett square and fill the chart.


BB*bb



Big image

Step 5:

list all phenotypes of the cross.


phenotype(physical appearance)- (B) all 4 offspring will have a 100% dominant trait.