1. Genetics
The study of heredity

2. Heredity
passing traits (characteristics) from parents to their children
What you see being passed on
Done through the process of meiosis and fertilization

3. Genes Genes Information on a chromosome that codes for specific traits
Come in pairs
One from mom and one from dad
One is usually more powerful than the other

4. Alleles Different form of the gene For example: Trait is height
Alleles are tall (T) and short (t)

5. History of Genetics Gregor Mendel Austrian Monk
More than 100 years ago
Worked with pea plants

6. Pea Plants Worked with Flower color Flower position Seed color
Seed shape
Pod shape
Pod color
Stem length

7. Mendel’s garden

8. Types of Traits Dominant Recessive
Traits that are more powerful and are the ones you see
They are represented by capital letters
Recessive
Traits that are hidden, or covered up, when there is a dominant trait
They are represented by lower case letters

9. Representing Genes Homozygous
This pea plant is short. It inherited 2 genes for shortness – one from the mom and one from the dad.
Homozygous
Having 2 identical alleles for the same trait
This pea plant would be represented by the letters - tt

10. Representing Genes Heterozygous-
Having 2 alleles that are not identical for the same trait
This pea plant would be represented by the letters - Tt
This tall pea plant has inherited one tall gene from one parent and one short gene from the other parent

11. Genotypes
An organism’s combination of genes for a trait is called its genotype
The genotype is represented by letter combinations
The possible choices are 2 capital letters, 2 lower case letters or 1 capital letter and 1 lower case letter
Examples: TT, tt, Tt

12. Phenotypes
What an organism looks like as a result of its genes (photograph, picture)
For example:
A pea plant that is TT would look tall,
A pea plant that is Tt would look tall,
A pea plant that is tt would look short

13. Time for a Lab
Reebops

14. Punnet Squares
Punnet squares are models used to explain genetic crosses
The letters across the top and down the left side represent the parents genes

15. How do you make a Punnet Square?
Draw a chart with 4 boxes
Across the top put the symbols for the mother’s genotype
Down the side put symbols for the father’s genotype
Use the cross Aa x Aa –--- A= Round and a = wrinkled

16. Here is our example
Now let’s look at the information inside the boxes. A=purple, a= white
What would the phenotype be for the letters AA?
What would the phenotype be for the letters Aa?
What would the phenotype be for the letters aa?

17. Incomplete Dominance
When a heterozygous genotype (Rr) shows a new phenotype which is in between the two parents
A red (RR) snapdragon crossed with a white (rr) snapdragon gives you a pink (Rr) snapdragon

18. Incomplete Dominance The Punnet square example.
Note the new genotypic ratios.
1:2:1