1. Mendelian Genetics

2. Gregor Mendel Born in 1822 in the Czech Republic
Studied at university of Vienna
Worked with PEAS in his monastery garden.
Started the first official true-breeding = plants that are self pollinated for generations. Result in genetically identical plants (clones).

3. Genetics=The Study of Heredity
He cut off the Male parts of each flower on a plant to do his experiments. This made sure that they bred with a flower group that was genetically different.
For each trait (physical characteristic) everything has two forms of a gene (also called alleles). One from the mother. One from the father.
Bred together plants that had different traits to create hybrids.

4. How to do a Monohybrid Genetic Cross
Must figure out how the alleles will interact with one another when mixed.
One type of interaction is complete dominance
The Principle of Dominance= Some alleles are dominant and some are recessive.
Dominant Allele Recessive Allele
This trait is always This trait will only be
expressed (shown) expressed if there are
if it is present two recessive alleles
and no dominant alleles

5. Punnett Squares
Figures out the Genotypes (combination of alleles) of the parents and offspring and also the resulting Phenotypes (the actual trait or characteristic we are talking about)
Since only one allele will be passed on to the next generation the chances of passing on each allele is segregated.
The Principle of Segregation = states that only one allele from each parent can be passed on. The two different alleles for a trait are segregated into different gametes
Parents are the F1 generation and the offspring are the F2 generation.

6. Monohybrid Cross using a Punnett Square
Tall alleles (T) are dominant to short alleles (t) in a pea plants.
Lets find out what will happen if we cross a true-breeding tall plant TT with a true-breeding short plant tt
Genotypic ratio of offspring:
Phenotypic ratio of offspring:
What will happen if we cross two tall plants that are heterozygous.

7. Put one parent on top of the square and one on the side
Bring the above alleles to the boxes below
Match up the side alleles by bringing them across.

8. Heterozygous vs Homozygous
What is a homozygote?
- how many different types are there?
What is a heterozygote?
- What is the genotype of the heterozygote?

9. Who’s the Daddy?
Genotypic Ratio:
Phenotypic Ratio:
- Perhaps the hardest part of doing a Punnett Square is figuring out what genotype the parents on the outside of the square will be.
Homozygous dominant vs. Homozygous Recessive
Homozygous Dominant vs. Heterozygous
Homozygous recessive vs. Heterozygous
Heterozygous vs. Heterozygous

10. Taking Your Chances.
If a monohybrid cross between two heterozygotes is conducted what are the chances/what is the percentage that you child will have the dominant phenotype?
How about the recessive trait?

11. Genetic Disorders Occur for a number of reasons - Mutation
- In-Breeding (lack of genetic diversity)
- Virus
Sickle Cell Anemia
Hemophilia
Diabetes
Tay-Sachs
PKU
Cystic Fibrosis
Huntington’s Disease
You can be a carrier for a disease and still not
have it. How is this possible?

12. Monohybrid vs Dihybrid Crosses
A monohybrid cross can only have 4 spaces within its Punnett Square.
A dihybrid cross will have 16 spaces?
A dihybrid cross looks at two traits. The human body is thousands upon thousands of traits.
DO NOT WRITE THIS, BUT THINK!!!!!!
How many spaces would there be if you accounted for all of these traits within one cross?

13. Pick Two Traits:
Lets cross two individuals who are heterozygous for both traits.
What is the Genotype of the mother and the father?

14. Put All of those Possibilities into a Single Cross:

15. Characteristic Ratios:
When conducting a dihybrid cross between two individuals who are heterozygous for both traits, what will be the phenotypic ratio of the offspring?
9 : 3 : 3 : 1

16. Complex Genetics So far we have only talked about COMPLETE DOMINANCE.
There are other types of interactions between alleles in a heterozygote:
-Complete Dominance
-Incomplete Dominance
-Co-Dominance
-Multiple Alleles

17. Incomplete Dominance
The heterozygote has a phenotype half-way between the dominant and recessive phenotypes.
The phenotypes blend.
Ex: tt = short & TT = tall then Tt = medium
RR = red & rr = white then Rr = pink

18. Co-dominance Both of the phenotypes involved are expressed.
Black Horse X White Horse = Zebra
Red X White = Red and white polka dots or
stripes
RED WHITE ROAN

19. Results in 4 Different Phenotypes
Multiple Alleles
There are more that two (T & t) alleles. You would have three different alleles. (A & B & C).
A, B, O blood-typing. Different
Phenotypes: AA Ao AB Bo BB oo
Results in 4 Different Phenotypes

20. Multiple Alleles Example:
What is the phenotypic ratio of the blood types of the offspring when two parents are crossed: the father is heterozygous for A type blood and the mother is heterozygous for B type blood?

21. Rules for Making a Pedigree
A Blank Circle = Female without the trait
A Shaded Circle = Female with the trait
A Blank Square = Male without the trait
A shaded square = Male with the trait

22. Sex-Linked Traits Many are found to be on the X chromosome.
The Y chromosome is smaller and has no allele to donate.
As a result whatever trait is on the X chromosome is expressed(even if it’s recessive).

24. Color Blindness: A Sex-linked Trait
A colorblind male and a female who is a carrier for color blindness have a child. What are the chances the child will be color blind?
Is it possible for a girl to be color blind?

25. Don’t forget to add the genetic disorders to your cheat sheets!!!!