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

2. 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.

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

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

5. 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)

6. 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”

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

8. 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

9. Traits Mendel looked at

10. Monohybrid Cross

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

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

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

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

16. 2 purple–flowered offspring from F1 generation yields:
F1 generation
hybrid offspring
¼ white
¾ purple

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

18. 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!