1. Warm ups: Which of the following has purebred alleles?
a. Bb b. Tt c. Blue d. BB
Which of the following would be the phenotype for blue eyes?
a. Bb b. blue c. BB d. bb
Which of the following would be the genotype for a hybrid brown eyed person?
a. Brown b. BB c. Bb d. bb

2. Important Vocabulary Review
Homozygous – when you have two of the same genes for a particular trait
You are PUREBRED (2 dominant or 2 recessive)
TT (tall) tt (short) BB (brown eyes)
Heterozygous – When you have two different genes for a particular trait
You are Hybrid (always 1 dominant and 1 recessive)
Tt (tall) Bb (brown eyes)

3. Homozygous and Heterozygous Practice Problems
T = tall t = short
B = brown eyes b = blue eyes
Homozygous tall: _________________
Homozygous short: _______________
Heterozygous tall: ________________
Homozygous brown eyes: __________
Heterozygous brown eyes: _________
Homozygous blue eyes: ___________ TT tt Tt BB Bb bb

4. Homozygous and Heterozygous Practice Problems
7. For each genotype below, indicate whether it is heterozygous (He) or homozygous (Ho)
TT ____ Bb ____ DD ____ Ff ____
Tt ____ tt _____ dd ____ Dd ____
BB ____ FF ____ ff _____ bb _____
8. Which of the genotypes would be considered purebred? _______________________________________________
9. Which of the genotypes would be considered hybrids? ________________________________________________ Ho He Ho He Ho He Ho He Ho Ho Ho Ho
TT, DD tt, BB, FF, dd, ff, bb
Bb, Ff, Tt, Dd,

5. How to predict traits in offspring
Punnett Squares
How to predict traits in offspring

6. Punnett Squares Punnett Squares – a grid showing genetic material
Shows probability, not actual results
Uses percentage to predict what might happen to the offspring
0 %, 25%, 50%, 75% or
100%

7. Punnett Square Problems
T = tall t = short
A heterozygous tall man has children with a homozygous short women.
Step 1: Write down the genotypes of the parents
Father = _________
Mother = _________ Tt tt

8. Step 2 – Draw a box and put a line going down and across

9. Step 3 – Put a pair of genes on top of box and a pair on the left hand side
t t T t

10. Step 4 – bring letters down and across

14. Completed Punnett Square
End result:
_____ tall
_____ short T
50 % Tt Tt
50 % Tt t tt tt

15. B = brown eyes b = blue eyes A father is homozygous for brown eyes and the mother is homozygous for blue eyes. What is the expected outcome? BB
Father = ______
Mother = ______
b b bb B B b
100 B b
____ % heterozygous
____ %
homozygous B B b B b

16. G = Green pea g = yellow pea A heterozygous green pea plant is crossed with homozygous green pea plant. What is the expected outcome? Gg
Plant 1 = ______
Plant 2 = ______
G g GG 50 G G G G g
____ % heterozygous
____ %
homozygous 50 G G G G g

17. T = tall t = short A mother and father are both heterozygous for being tall.75
____ % tall
____ % short 25 t T t t t

18. C = curly hair c = straight hair A dog that is purebred for straight hair is bred with a dog that is hybrid for curly hair. cc
Dog 1 = ______
Dog 2 = ______
c c Cc C C c C c 50
____ % purebred
____ % hybrid 50 c c c c c