1. Blood Types and Skin Colors
Incomplete Dominance and Co-Dominance

2. Non-Mendelian Inheritance
Multiple alleles = trait is determined by more than two alleles (ex. Human blood types)
Polygenic traits = trait influenced by several genes (ex. Human eye color, weight, skin tone)
Incomplete dominance = one allele is not completely dominant over the other and the two phenotypes blend together in the heterozygote (Ex: flowers…red, white, pink)
Co-dominance= both alleles for a gene are expressed when present in the heterozygote (Ex: cattle…red, white, roan coat)

3. Example 1: Flowers
Example: Snapdragons can be red, white, or pink (heterozygous).
Incomplete dominance - neither allele is dominant, red x white = pink
Use all capital letters - Red (RR) x White (WW) = Pink (RW)
What traits followed this one in the “Making Faces” lab?
Hair color, skin color, eye color, mouth size, eye distance, hair texture

4. Example 2: Fish Coloration
Co-Dominance- both alleles are expressed in the heterozygote
In a certain fish, blue scales and red scales are co-dominant.
When a fish has the genotype B R, it has a patchwork of blue and red scales.
What happens if you breed this fish with a fish that only has Blue Scales?

5. Example 2: Fish Coloration
 Step 1: Determine the genotypes of the parents RR = Red, BB = Blue, RB = patchwork fish
Step 2: Set up the Square
Step 3: Count the number of each phenotype:
1/2 will by patchwork
1/2 will be blue

6. Fish Coloration Practice
What happens when you cross two patchwork fish? (Draw the Punnett square, list phenotypes and percentages of each)

8. Special Inheritance: Human Blood Types
Austrian Karl Landsteiner discovered human blood groups
Even animals have blood types

9. Blood Type is Controlled by 3 Alleles
4 Possible Blood Types
Alleles: IA, IB, i
Special Inheritance:
IA & IB are co-dominant
i (type O allele) is recessive
Phenotype
Genotype(s)
Type A blood
IAIA or IAi
Type B blood
IBIB or IBi
Type AB blood
IAIB
Type O blood ii

10. Genotypes & Phenotypes

11. Blood Type Antigens

12. Blood that has antibodies on it that is not recognized by the body will be attacked by your immune system
AB is the Universal Acceptor – it has no anti-A or anti-B antigens
O Is the Universal Donor – it has not A or B antibodies and cannot be attacked

13. Consider Both Parents
Type A (genotype IAIA) x Type O (genotype ii)

14. Rh Factor
A person can either be Rh + or Rh –
(positive is dominant)

15. Rh Factor and Pregnancy
*Problem: When a fetus is Rh+ and the mother is Rh-, this can cause the mother’s immune system to attack the fetus. There are drugs that will suppress this. reaction.

17. Blood Type Test

18. Classwork Answer questions 1-8 on your own!
Please ask me for help as needed
The unfinished questions will be homework

19. Punnett Square Strategy
Read the question
Pick out the traits and dominant / recessive (underline)
Find information about the parents (circle)
Write down the letters and what they stand for (Capital letter = dominant)
Write down the parents’ genotype
If two traits, FOIL to get all possible combination
Complete the Punnett square
Choose the right size (2x2 or 4x4)
Put the parents’ genes on the outside
Combine the genes in the boxes
Interpret the Punnett square
Answer the question
Circle your answer

20. Punnett Square Strategy
Read the problem. Look for:
The dominant & recessive trait (with letters, sometimes)
Information about the parents
Write down our allele letters & what they stand for (ex: f = faint, F = not fainting)
Write out the parents’ genotypes
If it’s a two gene cross, FOIL to get all of the possible combinations
Make and solve the Punnett square
Choose the right size (2x2 or 4x4)
Put the parents’ genes on each side
Cross the traits
Interpret the Punnett square
See what the question is asking for
Circle your answer