1. April 2008 Mendelian Genetics March 6, 2009 Mr. Bromwell

2. Genetics Genetics – the scientific study of heredity. – Studied for centuries Artificial selection (i.e. breeding) Domestication – Blending hypothesis traits Could not account for unexpected traits trait A trait is a characteristic that can be passed from parent to offspring.

3. Gregor Johann Mendel Gregor Johann Mendel (1822-1884) 1822 - Born in Heizendorf, Austria 1843 - Enters monastery Studied physics, math, chemistry, botany, paleontology, & plant physiology Fails professorial exam 1860s – returns to monastery – Studies inheritance of traits in pea plants. – Uses 20,000 plants – Refutes blending hypothesis

4. Why Peas? Mendel choose peas because… … they are easy to grow. … they reproduce rapidly. … they were readily available. … the structure of pea flower enabled him to control fertilization. … they possessed distinctive traits that could be easily distinguished.

5. The Sex Lives of Peas

6. self-fertilization Pea plants usually reproduce by self-fertilization. – leads to “true-breeding” or “pure- breeding” plants cross- pollinate Mendel could easily cross- pollinate pea plants by hand. – can result in “hybrids” Pea flower

7. Mendel’s Experiment

8. Mendel’s Hypothesis 1.Each trait is controlled by a ‘factor.’ – since there were two distinct traits possible, there must be two distinct factors allele gene – ‘factor’ is called an allele – alternative forms of a single gene, or region of a chromosome that codes for a trait. 2.Alleles are paired in each plant. 3.If an organism has two different alleles for a trait, only one is shown. – dominant allele – dominant allele – fully shown (expressed) – recessive allele – recessive allele – masked by the dominant allele

9. References Biggs, Alton, et. al. Biology. New York: The McGraw Hill Companies, Inc., 2007. Fairholm, Rebsie. "Daughter of the Soil." [Weblog How to breed your own garden peas] 20 May 2007. 2 Apr 2008.