1. Punnett Squares
Write on the right side

2. * Remember alleles can be dominant or recessive.*
Different versions of genes are called alleles
* Remember alleles can be dominant or recessive.*

3. Punnett Square
A graphic used to predict the possible genotypes of offspring.
Think about it:
Each parent has 2 alleles for each gene. Their offspring receive one of those alleles from each parent (so the offspring also have 2)
Punnett squares show us a possible combination the offspring will receive

4. Getting a Better Understanding
Punnett squares
Getting a Better Understanding
The letters on top show one parent’s alleles for that trait
The letters on the side show the other parent’s alleles for that trait
Each box shows a possible combination the offspring will have

5. Making Predictions
Punnett squares help us find probabilities of certain genotypes. (a probability is the chance of getting a certain outcome in relation to the total number of outcomes)
We usually use ratios or percentages to represent probabilities.
percentage
25%
50%
1 out of 4
1:4
2 out of 4
2:4
ratio
50%
2 out of 4
2:4
25%
1 out of 4
1:4

6. Now Let’s practice
Fill in each box in the Punnett squares with the combination of alleles that the offspring would have.
A A
T t a T t

7. Now Let’s practice
Now find the probabilities of each outcome and write them in the blanks below.
A A
T t Aa Aa TT Tt a T t Aa Aa tt Tt
AA_____ Aa_____ aa_____
TT_____ Tt_____ tt_____

8. Reflection
Complete the “Do the Math: You try it” questions on page 449 in your textbook.
Cut out that section and glue/tape/staple it on the left side of your journal next to your Punnett Square notes