Exploring Heredity Through Mendel's Garden Pea Experiments

1. Chapter 8 Section 1: The Origins of Genetics Grade 10 Biology Spring 2011

2. Bell Ringer • Make a list of 5 characteristics that are passed on in families • Name one characteristic that may also be inherited but that is also influenced by behavior or environment

3. Objectives • Identify the investigator whose studies formed the basis of modern genetics • List characteristics that make the garden pea a good subject for genetic study • Summarize the three major steps of Gregor Mendel’s garden pea experiments • Relate the ratios that Mendel observed in his crosses to his data

4. Mendel’s Studies of Characters • Heredity: the passing of characters from parents to offspring

5. Mendel’s Breeding Experiments • Gregor Mendel: grandfather of genetics • Carried out experiments with the garden pea plant • Genetics: the branch of biology that focuses on heredity

6. Mendel’s Breeding Experiments • T.A. Knight • Crossed a variety of the garden pea that had purple flowers with a variety that had white flowers • All of the offspring of Knight’s crosses had purple flowers • When 2 of the purple flowered offspring were crossed, their offspring showed both white and purple flowers • White trait had reappeared

7. Mendel’s Breeding Experiments • Mendel’s experiments differed because he counted the number of each kind of offspring and analyzed the data

8. Useful Features in Peas • Several characters of the garden pea exist in two clearly different forms • Character = inherited characteristic, such as flower colour • Trait = refers to single form of a character, such as purple flowers

9. Useful Features in Peas • Male and female parts of a garden pea plant are enclosed within the same flower • Can control mating • Small, grows easily, matures quickly, and produces many offspring

10. Traits Expressed as Simple Ratios • Monohybrid cross: cross that involves one pair of contrasting traits • True breeding: all of offspring would display only one form of the character • Done by allowing a variety of peas to self pollinate for several generations • P Generation: first two individuals that are crossed in a breeding experiment

11. Traits Expressed as Simple Ratios • F1 Generation: the offspring of the P generation • F2 Generation: the offspring of the F1 generation

12. Mendel’s Result • F1 generation  showed only one form of the trait • F1 generation allowed to self-pollinate • Missing trait reappeared in the F2 generation

13. Mendel’s Result • F2 Generation: • 705 purple • 224 white • 705:224 or 705/224 • Reduced = 3:1 • He found the same results for each of the other 7 traits he studied