Chapter 8 Mendel and Heredity Section 8-1 The Origins of Genetics

Objectives A. Identify investigator that formed basis of genetics B. List characteristics that make garden pea good subject for genetic study C. Summarize 3 major steps of Gregor Mendel’s garden pea experiments D. Relate ratios that Mendel observed in his crosses to his data.

Characteristics Passed On A. Eye color B. Skin color C. Hair color D. Height E. Face & nose shape

Inherited but also influenced by behavior or environment A. Muscle size B. Body weight C. Sun tan D. Cholesterol level E. Talents

Gregor Johanna Mendel 1. “Father of Genetics” 2. Parents=peasants, he learned AG 3. Studied theology (Austrian Monk) 4. Studied math/science at Vienna 5. Experimented w/pea plant (Pisum sativum)

T.A. Knight experimented w/pea plant Crossed purple flowers w/white Results: white showed up in 2nd generation Purple=“stronger tendency” Phrase “it’s in the blood”

D. Relation to Mendel? 1. Repeated Knight’s experiments BUT counted offspring AND analyzed data

garden pea=good subject for studying heredity A. Several characters exist in 2 different forms B. Male & female reproductive parts in same flower (control mating) C. Small D. Grow easily E. Mature quickly F. Many offspring

Traits Mendel looked at

Monohybrid Cross

Mendel’s 3 Steps Step 1 Self-pollinate=true-breeding P generation (parental generation) 1st 2 individuals crossed

Step 2:Cross-pollinated P generation a. Purple flowers & white b. Offspring=F1 generation c. Recorded # of F1 plants expressing each trait

Step 3: F1 generation self-pollinated a. Offspring of F1 generation=F2 generation b. Each F2 plant counted & recorded

Results of Mendel’s experiments 1. White–flower w/purple–flowered yields:  P generation purebred parents F1 generation (first filial) all purple

2 purple–flowered offspring from F1 generation yields:  F1 generation hybrid offspring ¼ white ¾ purple

Data = 705 purple:224 white Reduced= 705/224= 3.15= 3:1 ratio of purple to white

VIII. In Review of 8-1 Mendel=“Father of Genetics” Pea plant=small & easy to breed, good subject for study Although he made amazing discoveries in the world of genetics, his work went unnoticed for generations!