1. Genetics the scientific study of heredity.

2. Many of your physical traits resemble those of your parents
Many of your physical traits resemble those of your parents. These are physical or behavioral characteristics that vary from one individual to another.
Heredity can be defined as the passing of genetic traits from parents to offspring.
Question: Which one of the president’s daughters looks more like their mother?
Traits

3. Gregor Mendel
Gregor Mendel was an Austrian monk and a scientist who performed experiments with garden peas.
Mendel studied seven pea plant traits, each with two contrasting characters.
He crossed plants with each of the seven contrasting characters and studied their offspring.

4. Mendel’s Crosses
Each original pair of plants is the P (parental) generation.
The offspring are called the F1, or “first filial,” generation.
The F1 hybrid plants all had the character of only one of the parents.

5. Mendel’s Seven Traits
Mendel's first conclusion was that biological inheritance is determined by factors that are passed from one generation to the next.
He called these factors genes.
Each of the traits Mendel studied was controlled by one gene that occurred in two contrasting forms that produced different characters for each trait.

6. Principle of Dominance
The different forms of a gene are called alleles.
Mendel’s second conclusion is called the “Principle of Dominance.” which states that some alleles are dominant (expressed) and others are recessive (masked).

7. Mendel suggested that the alleles segregate from each other during the formation of the sex cells, or gametes.
Gamete Formation

8. Try writing your own PUN for extra credit.

9. Mendel’s Principles
1) Genes are passed from parents to their offspring.
2) If two or more forms (alleles) of the gene for a single trait exist, some forms of the gene may be dominant and others may be recessive.
3) In most sexually reproducing organisms, each adult has two copies of each gene. These genes are segregated from each other when gametes are formed.
4) The alleles for different genes usually segregate independently of one another.

10. Probability, Ratios and Punnett Squares
The likelihood that a particular event will occur is called probability.
Probability can be used to predict the outcomes of genetic crosses.
Punnett squares are diagrams used to predict and compare the genetic variations that will result from a cross.

11. Punnett Square Practice
To determine the phenotype of an offspring you must first recognize its genotype.
We have discussed two types of alleles, Dominant (B) and Recessive (b)
We have also discussed Heterozygous (Bb) and Homozygous (BB) or (bb) alleles
Punnett squares provide a means for determining the phenotypic outcome resulting from the combination of gametes
The basic construction of a simple punnet square is to the left of this explanation.
Punnett Square Practice

12. List the phenotype and genotype outcomes for each cross below using the Punnett Square.
Practice Problems
Heterozygous dominant x Homozygous recessive
Hh x hh ( H = white, h = green )
homozygous recessive x homozygous recessive
bb x bb ( B = Black, b = brown)
Heterozygous dominant x homozygous dominant
Tt x TT ( T = tall, t = short )

13. Probability and Predicted Averages
• Probabilities predict the average outcome of a large number of events. • In genetics, the larger the number of offspring, the closer the resulting numbers will get to expected values.
Cat example from class. Mom and Dad were BbxBb had 25 kittens of black and white color

14. Incomplete
Dominance
When one allele is not completely dominant over another it is called incomplete dominance.
In incomplete dominance, the heterozygous phenotype is between the two homozygous phenotypes.

15. Codominance In codominance, both alleles contribute to the phenotype
(like spots!).
Heterozygous chickens are speckled with both black and white feathers. The black and white colors do not blend to form a new color, but appear separately.

16. Multiple
Alleles
•An individual can’t have more than two alleles. (Only two parents….) However, more than two possible alleles can exist in a population.
•A rabbit's coat color is determined by a single gene that has at least four different alleles.
- Blood types in humans (A, B, and O)

17. Polygenic Traits
Traits controlled by two or more genes are said to be polygenic traits.
•Skin color in humans is a polygenic trait controlled by more than four different genes. Scientists do not believe they have identified all the genes responsible for eye color.

18. REVIEW
The name of the scientist responsible for forming the foundations of genetics is __________.
Why did this scientist chose garden peas to perform his experiments?
Heredity can be defined as ________
Genetics can be defined as _______
What is difference between dominant and recessive traits?
Explain the difference between the P, F1 and F2 generations. What type of genetic characteristics can be observed in each one?
The difference between a gene and an allele is?
Homozygous is?
What is codominance?
What is incomplete dominance?

19. Sex-Linked Traits

20. LOL Some traits are linked on the sex chromosomes.
These are typically on the X chromosome
This means that even if it is a recessive trait, it will show up in a male individual.
Examples: male pattern baldness, hemophilia and specific color patterns in chickens

21. X linked codominant traits
Some of these traits are linked on the X chromosome and you need two for the trait to show up.
Calico cats are always female
This is a codominant X- linked trait
The calico coloring is completely random
Cloned calico cats have a different coloring than that of the cat they were cloned from.

22. Pedigrees
Pedigrees show how traits are passed through families
We draw pedigrees by going backwards from the trait that we want to trace
First you show which people have the trait
Then you figure how the trait was passed from parent to offspring
Key:
Blank = no trait
Filled in = affected
Squares = MALE
Circles = FEMALE

23. Hemophilia in the Royal Family

24. Two Factor Hybrid Cross
For a two-factor F1 hybrid cross, the Punnett square predicts a : 3 : 3 : 1 ratio in the F2 generation.