Introduction to Genetics Chapter 11 Introduction to Genetics

Golden Doodle Blending Theory offspring are a straight mix A Brief History In the past, people did not understand how traits were inherited, but there were many guesses based on things that could be observed. Two theories emerged…. Blending Theory offspring are a straight mix Particulate Theory traits are inherited as "particles", offspring receive a "piece" from each parent, some pieces may hide the others Golden Doodle

Who was Gregor Mendel? GENETICS study of heredity HEREDITY He was known as the “FATHER OF GENETICS” He discovered how traits were inherited. GENETICS study of heredity HEREDITY the passing of traits from parents to offspring

Mendel’s Peas Mendel did his study on pea plants which have many traits: - tall/short - purple/white flowers - round/wrinkled seed

Mendel’s Experiments Example Mendel conducted self-pollination and cross pollination to observe expression of pea plant traits. Example

Mendel’s Pea Plant Experiment P1 Generation F1 Generation F2 Generation Tall Short Tall Tall Tall Tall Tall Short Cross Pollination Self Pollination Final Results

Mendel’s Results F1 plants = 100% tall F2 plants = 75% tall, 25% short Similar results occurred when each trait of a pea plant was isolated. Ex. Yellow/green seeds smooth/wrinkled seeds

Mendel’s Conclusions Traits are passed on by genes from parent to offspring. Principle of Dominance & Recessiveness - one trait may hide the expression of another trait. - Dominant- trait that is always expressed if present. - Recessive- trait that is hidden if a dominant trait is present.

3. Principle of Segregation - genes are separated during sex cell production. 4. Principle of Independent Assortment - alleles(forms of a gene) are separated independently to sex cells. Different traits are not linked together. Ex. Seed color with plant height