Human Cerotype
Jun 15, 2015
Human Cerotype
Punnett Squares
How to predict traits in offspring
Important Vocabulary
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: ___________
Bikini Bottom Genetics
1. 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 _____
2. Which of the genotypes would be considered purebred? _______________________________________________
3. Which of the genotypes would be considered hybrids? ________________________________________________
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
1. A heterozygous tall man has children with a homozygous short women.
1. Write down the genotypes of the parents
Father = _________
Mother = _________
Tttt
Step 1 – Draw a box and put a line going down and across
Step 2 – Put Mother’s genes on top of box and father’s on left hand side
t t
T
t
Step 3 – 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
How to Make a Punnett Square.
1. Draw a square and divide it into 4 sections.
2. Write the genotypes for one parent on the top and one down the side.
3. Fill in the sections with one allele from top and one from the side.
4. Figure out the percentages (each box is worth 25%)
Try making your own P-square!
Incomplete Dominance
• There’s always an exception to the rule!
• Genes are the same way. There are times when a blending of the genes occur.
• Skin color or Flower color often does this.
WHITERED
AND
PINK
Word Definition Picture
Incomplete Dominance
When two traits blend
RED A
ND
PINK