1 Gregor Mendel ( ) The Father of Genetics

Gregor Johann Mendel  Austrian monk  Studied the inheritance of traits in pea plants  Developed the laws of inheritance  Mendel's work was not recognized until the turn of the 20th century 2

Gregor Johann Mendel  Between 1856 and 1863, Mendel cultivated and tested thousands of pea plants  He found that the plants' offspring retained traits of the parents 3

4  Mendel stated that physical traits are inherited as “particles”  Mendel did not know that the “particles” were actually Chromosomes & DNA Particulate Inheritance

Why peas, Pisum sativum?  Can be grown in a small area  Produce lots of offspring  Produce pure plants when allowed to self- pollinate several generations  Can be artificially cross- pollinated 5

Mendel and His Peas Mendel tested 7 traits: 1. Flower color 2. Flower position 3. Seed color 4. Seed shape 5. Pod shape 6. Pod color 7. Plant height

Mendel and His Peas Mendel crossed flowers that were true-breeding for each characteristic. He crossed a purple (PP) flowered plant with a white (pp) flowered plant. (Parent Generation)

Mendel and His Peas The first generation (F1) of plants all had purple flowers. Where did the white color go?? (Pp) (Pp) Purple Parent (PP) White Parent (pp)

Mendel and His Peas Mendel took two of his first generation (F1 x F1) purple flowered plants and crossed them together. In the second generation (F2) he had 3 purple flowered plants, and 1 white flowered plant. (PP) (Pp) (pp) Purple Parent (Pp)

Mendel and His Peas Mendel noticed in the first generation, all of the white flowers seemed to disappear. He called this a recessive trait. The white color faded into the background at first. It showed up in the next generation when he pollinated the flowers.

Mendel and His Peas The color (purple) that seemed to mask over the recessive color was named the dominant trait.

Mendel and His Peas Mendel was responsible for figuring out that each plant carried two sets of instructions for each characteristic (one from the “mom” and one from the “dad”). Like many scientists, his work was not accepted until after his death.

Let’s Review 1. If you crossed a true-breeding black rabbit with a true-breeding white rabbit, all of the offspring would be black. Which trait is dominant in rabbits: black fur or white fur? 2. Which trait is recessive?

Answer The trait for black fur is dominant over the trait for white fur. The white fur trait is recessive. (Bb) (Bb) (Bb) Black Rabbit (BB) White Rabbit (bb)

Google’s tribute to Mendel July 2011

What Did Mendel Find? He discovered different laws and rules that explain factors affecting heredity.

Rule of Unit Factors Each organism has two alleles for each trait Alleles - different forms of the same gene Genes - located on chromosomes, they control how an organism develops

Rule of Dominance The trait that is visible in the offspring is the dominant trait (uppercase) The trait that disappears in the offspring is the recessive trait (lowercase)

Law of Segregation The two alleles for a trait must separate when gametes are formed A parent randomly passes only one allele for each trait to each offspring

Law of Independent Assortment The genes for different traits are inherited independently of each other.

Mendel and His Peas Vocabulary 1. Heredity- the passing of traits from parent to offspring. 2. Self-pollinate- A plant is often able to pollinate by itself because it contains both the male and female reproductive structures. This only requires 1 parent.

Mendel and His Peas 3. True-breeding- all of the offspring will have the same trait as the parent when self-pollinated 4. First-generation- the very first set of offspring from two parents 5. Dominant trait- the trait observed when at least one dominant allele for a characteristic is inherited

Mendel and His Peas 6. Recessive trait- a trait that is apparent only when two recessive alleles for the same characteristic are inherited 7. Genes- a segment of DNA that carries hereditary instructions and is passed from parent to offspring 8. Alleles- multiple forms of the same gene

Mendel and His Peas 9. Genotype- an organisms inherited combination of alleles 10. Phenotype- an organisms inherited appearance