1. What did Mendel observe? How do alleles affect inheritance?
What is Heredity?
What did Mendel observe?
How do alleles affect inheritance?

2. Priest in a European monastery that did experiments with Pea plants
Gregor Mendel
Priest in a European monastery that did experiments with Pea plants
Studied heredity, the passing of genetic instructions from one generation to the next

3. Genetics Mendel’s discoveries were the foundation of genetics
Specific characteristics of an organism are called traits

4. The pistil produces female sex cells
In Pea Plants…
The pistil produces female sex cells
Stamen produce pollen – male sex cells
Fertilization is when egg and sperm cells join
Pollination is how the pollen reaches the pistil

5. Purebred tall pea plants always come from tall parent plants
Purebred is the offspring of many generations that have the same form of a trait
Purebred tall pea plants always come from tall parent plants

6. Genes are found within the chromosomes in the nucleus of the cell
Genes and alleles
Today, scientists use the word gene to describe the factors that control a trait
Genes are found within the chromosomes in the nucleus of the cell

7. Genes and alleles continued
Alleles are different forms of a gene
The gene that controls plant height has one allele for tall and one allele for short

8. Dominant and recessive
An organisms traits are controlled by the alleles it inherits from its parents
Some alleles are dominant while other alleles are recessive

9. Dominant and recessive continued
Dominant allele – one whose trait always shows up when present
Recessive allele – hidden whenever dominant allele is present

10. expressed
We use the word “expressed” to describe the trait an organism inherits
A short pea plant has two recessive genes therefore, short is expressed

11. Symbols for alleles
Capital letters represent a dominant allele
Lowercase versions of the same letter are used for the recessive allele