1. Gregor Mendel
Experimented with pea plants and discovered some patterns of inheritance
Genetic Inheritance = passing genetic information from one generation to the next
Mendel ( )

2. Traits, Genes and Alleles
Trait = an inherited characteristic of a living thing
Examples: height and color
Gene = a piece of DNA that codes for a protein
Example: Gene for purple color in flower petals
Allele = different version of a gene (different DNA sequence)
Example: Allele for purple protein and white protein

3. Mendel’s Crosses

4. Mendel’s Crosses Mendel created plants that were pure-bred
Pure-bred plants are plants that have the same traits generation after generation
He mated, or crossed, 2 different pure-bred plants to produce hybrids
A hybrid is an organism that has two different types of DNA, usually 2 diff. alleles

5. Mendel’s Crosses
What do you expect in the next generation?

6. Mendel’s Principle of Dominance
For some genes, alleles can be dominant or recessive
Dominant alleles prevent recessive alleles from being seen (Symbol = Capital Letter)
Recessive alleles are only seen when they are the only copies of the gene (Symbol = Lowercase Letter)

7. Mendel’s Question:
Why did the white flower trait disappear in the F1 generation and re-appear in the F2 generation?
What do you expect in the next generation?

8. Mendel’s Explanation
Each organism has two versions of every gene (2 alleles)
1 allele is received from each parent

9. Mendel’s Explanation
Gametes are reproductive cells like sperm and eggs

10. Mendel’s Explanation
When a parent creates gametes, the two alleles segregate, or separate, and enter different gametes
Mendel named this idea the Law of Segregation

11. Mendel’s Explanation
When two hybrids are crossed, ¼ of the offspring will inherit two copies of the recessive allele

12. Questions
How does the prediction of 3:1 compare to Mendel’s experimental data?
Why might there be some differences?