1. PATTERNS OF HEREDITY CAN BE PREDICTED
PUNNETT SQUARES SHOW POSSIBLE OUTCOMES FOR INHERITANCE
RATIOS AND PERCENTAGES CAN EXPRESS THE PROBABLITY OF OUTCOMES.

2. PUNNETT SQUARE
Shows how the parent’s alleles might combine in offspring
Top of square shows one parent’s alleles for a trait (D,D for dominant tall); while side shows other parent’s alleles for the trait (d,d for recessive short)
Each box shows way the alleles from each parent would combine in offspring. (In this case, each child would be Dd, one dominant and one recessive, so they would all be tall.

3. Ratios can Express Probability
RATIO: compares the relationship between 2 quantities. 4:4 is four out of four
PROBABILITY: the chance of a specific outcome in relation to the total number of possible outcomes.

4. Percentages can Express Probability
PERCENTAGE: is a ratio that compares a number to 100. (the chance 2 hybrid black guinea pigs Bb, will have a recessive brown pig bb, is 25% or 25 out of Punnett square shows it as 1:4.
Punnett squares & probability do not guarantee the outcome, only predict an outcome.

6. Calculating Probability
Human females have 2 X-chromosomes (X,X) & males are (X,y). The punnett square shows only 2 possible outcomes (male-Xy or female-XX).
Punnett squares & probability only predict the likelihood of different outcomes, the actual experimental results may not match predicted outcomes.