1. Mendel’s Genetics
Mendel’s research provided the groundwork for our understanding of inheritance of traits.

2. Mendel’s Conclusions
Mendel's four conclusions – although there are exceptions, his conclusions apply to plants, animals and humans! Many of our deadly diseases are found to be carried on one recessive allele.
First Conclusion: biological inheritance is determined by factors that are passed form one generation to the next. Today we know these factors as genes.
Second Conclusion: Principle of dominance – Some alleles (forms of a gene) are dominant and some are recessive. An organism with a dominant allele for a particular form of a trait will always have that form.

3. Mendel’s Conclusions
Third Conclusion: Mendel's Law of Segregation = Each pea plant has 2 alleles (different forms of a gene) for each trait. One allele comes from each parent. This means, that during the formation of each gamete (egg and sperm), the two alleles must separate or segregate from each other. Each gamete only carries a single gene (allele).
Fourth Conclusion: Principle of Independent Assortment - genes for different traits can separate INDEPENDENTLY during the formation of gametes.

4. Real World Genetics
MOST traits are not inherited in such a simple manner as shown by Mendel. For example:
Many traits are controlled by more than one gene
Many alleles are neither completely recessive nor dominant
We now know a gene is actually a small section of a DNA molecule.

5. Jackalope = cross between a jack rabbit and an antelope
Exceptions to Mendel
Incomplete Dominance
Codominance
Multiple Alleles for a Trait
Multiple Genes for a Trait

6. Exceptions to Mendel
Incomplete dominance – neither allele is dominant.
For example: Red + White sometimes makes …

7. Incomplete Dominance
What CONCEPT does red + white = pink appear to follow? __________________
How does this differ from blending?
Genetics of four-o-clock flowers:
R = red allele
W = white allele
RR = red flower, WW = white flower, RW = pink flower
Blending

8. Incomplete Dominance
Draw a Punnett Square showing a cross between a red flowering four o’clock and a white flowering four o’clock.
What are the phenotypes and genotypes of the offspring?

9. Incomplete Dominance Phenotype: All of the offspring are pink
Genotype: All of the offspring are RW
Draw a Punnett Square showing a cross between two pink flowering four o’clock.
What are the phenotypes and genotypes of the offspring?

10. Incomplete Dominance Is this blending? Why or why not?
Have the alleles
(R and W) been
“blended away?”
Now show a cross
between a pink
and white flower. R W
RR RW
RW WW

11. Incomplete Dominance
Each allele in the example provides instructions to a cell for making an enzyme.
The R allele produces an enzyme necessary for the production of red pigment.
The W allele produces an enzyme necessary for the production of white pigment.
Both alleles are active in incomplete dominance.

12. Exceptions to Mendel
Codominance -neither allele is dominant or recessive.
Example:
variety of cattle with all red hair = RR
variety of cattle with all white hair = WW
A cross of a red cow with a white bull produces offspring (RW) that have both red and white hair

13. Codominance
Other examples: + =

14. Codominance
Other examples: +

15. Exceptions to Mendel
Multiple alleles: More than two alleles exist for a trait--however, each individual still only has two alleles.

16. Exceptions to Mendel Example: Hair Color
Some alleles, such as brown-ebony, produce enzymes with very high activity, which in turn produce a large quantity of the brown pigment.
Some alleles, such as brown-Swedish-blonde, produce enzymes with very little activity, which in turn produce only a small amount of the brown pigment.
All alleles fall somewhere on a continuum, from no activity to very high activity--which geneticists refer to as an allelic series.
In hair color, alleles with more activity are dominant to alleles with less activity. More activity —› more pigment —› hair color phenotype.

17. Multiple Alleles for a Trait
Example: Variations of a tabby cat

18. Multiple Alleles for a Trait
Example: Human Blood Groups
Before the 1900’s people thought all blood was the same. Fatalities resulted from
Transfusions of animal blood into humans!
Transfusions of some human blood to other humans

19. Multiple Alleles for a Trait
It was then discovered there are different types of red blood cells.
Human Blood Groups – Three alleles: A, B, O

20. Multiple Alleles – Blood Types
What are all of the possible genotypes using these three alleles? (Hint: Remember each person only has two alleles for a trait!!)
AA AO BB BO AB OO

21. Multiple Alleles – Blood Types
Genotypes Phenotypes
AA Blood Type A
AO Blood Type A
BB Blood Type B
BO Blood Type B
AB Blood Type AB
OO Blood Type O

22. Multiple Alleles – Blood Types
What is the difference between the phenotypes?
Type A = contains one type of antigen
Type B = contains a different type of antigen
Type AB = contains both types of antigens
Type O = does not contain any antigens

23. Multiple Alleles – Blood Types
Antigen: A foreign substance that triggers an immune response (production of antibodies)
Antibodies: part of the body’s defense for fighting off infection
Example: If a person has Type A blood, the antigen on his blood cells is NOT foreign to him.  the body does not produce antibodies.
Example: If Type B blood is transfused into a person with Type A blood or Type O blood, the body will attack the new blood cells as though they are an infection!

24. Multiple Alleles – Blood Types
Which blood type shows codominance?
_________
Which blood type is the universal donor?
Which blood type is the universal recipient? AB O AB

25. Multiple Alleles – Blood Types
Blood types in the United States are more or less common based on race and ethnicity.
However, Type O is most common among all groups and Type AB is least common.

26. Rh Factor Research conducted on rhesus monkeys.
Rh is a protein either found in the blood Rh+ or absent Rh-.
The Rh factor follows dominant/recessive patterns of inheritance.

27. Rh Factor
Mother-fetus incompatibility occurs when the mother is Rh- (dd) and her fetus is Rh+ (DD or Dd). 
Maternal antibodies can cross the placenta and destroy fetal red blood cells.  The risk increases with each pregnancy. 
Treatment: If you are Rh-, you will be given a shot of Rh immunoglobulin during pregnancy. It prevents the production of Rh antibodies.

28. Rh Factor Rh- : Found in 15% Europeans; 7% African Americans
Set up two Punnett Squares showing a cross between a father who is Rh+ and a mother who is Rh-.
What is the possibility of the Rh- mother producing a fetus that is Rh+?

29. Multiple Alleles – Blood Types
Complete Reading on Blood Types
Discuss articles with your group
Answer questions

30. Exceptions to Mendel Multiple genes for a single trait:
Example: height. Height is made up of the length of different sections of your body added together. Each section is controlled by a different gene.
Example: Eye color in humans. Controlled by interactions of at least 3 different genes.

31. Multiple Genes for a Single Trait
Skin color:
Scientists now believe that 3 genes control skin color.
You get 3 alleles from your mother and 3 alleles from your father for 6 alleles.
If all 6 of the alleles are for dark skin, you will have the darkest possible skin.
If you have 5 dark alleles and one light, you will have very dark skin.
If you have all 6 light alleles then you will have the lightest skin possible.

32. Exceptions to Mendel
Complete Worksheets
in Groups