1. Using a Punnett Square

2. Describe DOMINANT
A trait that covers over, or dominates, another form of that trait
Trait that always shows up, even when only one of the two alleles is in the dominant form
Shown by a capital letter

3. Describe RECESSIVE
A trait that is covered up, or dominated, by another form of that trait.
Hidden when the other copy of the gene contains the DOMINANT allele.
Shows up only when there is no dominant allele present
Shown with a lower-case letter

4. What is HOMOZYGOUS? Both alleles [forms of the gene] are the same.
Example:
When offspring inherit two dominant genes (RR), they are said to be homozygous dominant
When offspring inherit two recessive genes, (rr) they are said to be homozygous recessive

5. What is HETEROZYGOUS? When alleles occur in different forms Example:
When offspring inherit two different alleles, one dominant gene and one recessive gene (Rr), they are said to be heterozygous

6. Define GENOTYPE
An organism's genetic makeup – the specific combination of alleles for a gene received from parents.
Ex. – Rr, Hh, Tt

7. Define PHENOTYPE
Physical appearance or characteristics and behavior of an organism resulting from its genotype.
Ex. – eye color, hair color, shape of nose or ears.

8. What is a PUNNETT SQUARE?
A chart that shows all the possible combinations of alleles that can result when genes are crossed

9. What is a PUNNETT SQUARE?
Letters stand for dominant and recessive alleles
An UPPERCASE letter stands for a dominant allele. Ex. – R, T
A Lowercase letter stands for recessive alleles. Ex. – r, t

10. Using a PUNNETT SQUARE
To set up a Punnett square, draw a large square, and then divide it into 4 equal sections (also squares). It should look something like this:

11. Rr x rr Using a PUNNETT SQUARE
Now you need two parents to mate, ones with a known genotype
For example, a red flower (genotype Rr) and a white flower (genotype rr).
Rr x rr

12. Using a PUNNETT SQUARE
Place one of the parents on top, and one on the left. You should get something similar to this:

13. Using a PUNNETT SQUARE
Finally, take each letter in each column and combine it with each letter from each row in the corresponding square. You should now have a picture close to this:

14. Using a PUNNETT SQUARE
The two-letter combinations are the possible genotypes of offspring
For this example, they are: Rr, Rr, rr, and rr genotypes.
From this it is possible to determine the probability (chance) that a flower will have a red phenotype (2/4 or 50%) or a white phenotype (2/4 or 50%)