Warm ups:

1. Which of the following has purebred alleles?a. Bb b. Tt c. Blue d.

BB

2. Which of the following would be the phenotype for blue eyes?

a. Bb b. blue c. BB d. bb

3. Which of the following would be the genotype for a hybrid brown eyed person?

a. Brown b. BB c. Bb d. bb

Important Vocabulary Review

1. Homozygous – when you have two of the same genes for a particular trait

a. You are PUREBRED (2 dominant or 2 recessive)

b. TT (tall) tt (short) BB (brown eyes)

2. Heterozygous – When you have two different genes for a particular trait

a. You are Hybrid (always 1 dominant and 1 recessive)

b. Tt (tall) Bb (brown eyes)

Homozygous and Heterozygous Practice Problems

T = tall t = shortB = brown eyes b = blue eyes

1. Homozygous tall: _________________2. Homozygous short: _______________3. Heterozygous tall: ________________4. Homozygous brown eyes: __________5. Heterozygous brown eyes: _________6. Homozygous blue eyes: ___________

TTttTt

BBBb

bb

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 HeHe Ho Ho HeHo Ho Ho Ho

TT, DD tt, BB, FF, dd, ff, bb

Bb, Ff, Tt, Dd,

Homozygous and Heterozygous Practice Problems

Punnett Squares

How to predict traits in offspring

Punnett Squares

1. 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%

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

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

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

t t

T

t

Step 4 – bring letters down and across

Completed Punnett Square

End result:

_____ tall

_____ shortTt Tt

tt tt

tt

Tt

t t

T

t

50 %50 %

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?

Father = ______

Mother = ______

BB

bb b b

B

B B b

B b

B b

B b

____ % heterozygous

____ %

homozygous

100

0

G = Green pea g = yellow peaA heterozygous green pea plant is crossed with homozygous green pea plant. What is the expected outcome?

Plant 1 = ______

Plant 2 = ______

Gg

GG G g

G

G GG

GG

G g

Gg

____ % heterozygous

____ %

homozygous

50

50

T = tall t = short A mother and father are both heterozygous for being tall.

Father = ______

Mother = ______

Tt

Tt T t

t

T T T

T t

T t

t t

____ % tall

____ % short

75

25

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.

Dog 1 = ______

Dog 2 = ______

cc

Cc c c

c

C Cc

c c

C c

c c

____ % purebred

____ % hybrid

50

50