Chapter 8Chapter 8Mendel and Mendel and

HeredityHeredity

Section 8-1Section 8-1The Origins of The Origins of

GeneticsGenetics

Objectives Objectives

A. Identify investigator that formed A. Identify investigator that formed basis of geneticsbasis of genetics

B. List characteristics that make B. List characteristics that make garden pea good subject for genetic garden pea good subject for genetic studystudy

C. Summarize 3 major steps of Gregor C. Summarize 3 major steps of Gregor Mendel’s garden pea experimentsMendel’s garden pea experiments

D. Relate ratios that Mendel observed D. Relate ratios that Mendel observed in his crosses to his data.in his crosses to his data.

Characteristics Passed On Characteristics Passed On

AA. Eye color. Eye color

B. Skin colorB. Skin color

C. Hair colorC. Hair color

D. Height D. Height

E. Face & E. Face & nose shapenose shape

Inherited but also influenced by Inherited but also influenced by behavior or environmentbehavior or environment

A. Muscle sizeA. Muscle size

B. Body weightB. Body weight

C. Sun tanC. Sun tan

D. Cholesterol D. Cholesterol levellevel

E. TalentsE. Talents

Gregor Johanna MendelGregor Johanna Mendel1. “Father of Genetics”1. “Father of Genetics”

2. Parents=peasants, he learned AG2. Parents=peasants, he learned AG

3. Studied theology (Austrian Monk)3. Studied theology (Austrian Monk)

4. Studied math/science at Vienna4. Studied math/science at Vienna

5. Experimented w/pea plant (5. Experimented w/pea plant (Pisum Pisum sativumsativum))

T.A. Knight experimented w/pea T.A. Knight experimented w/pea plantplant

1.1. Crossed purple Crossed purple flowers w/white flowers w/white

2.2. Results: white Results: white showed up in 2showed up in 2ndnd generationgeneration

3.3. Purple=“stronger Purple=“stronger tendency” tendency”

4.4. Phrase “it’s in the Phrase “it’s in the blood”blood”

D. Relation to Mendel?D. Relation to Mendel?

1. Repeated 1. Repeated Knight’s Knight’s experiments experiments BUT BUT counted offspring counted offspring AND AND analyzed analyzed datadata

garden pea=good subject for garden pea=good subject for studying heredity studying heredity

A. A. Several characters exist in 2 Several characters exist in 2 different formsdifferent forms

B. Male & female reproductive parts in B. Male & female reproductive parts in same flower (control mating)same flower (control mating)

C. SmallC. Small

D. Grow easilyD. Grow easily

E. Mature quicklyE. Mature quickly

F. Many offspringF. Many offspring

Traits Traits Mendel Mendel looked atlooked at

Monohybrid CrossMonohybrid Cross

Mendel’s 3 StepsMendel’s 3 StepsStep 1Step 1 Self-pollinate=Self-pollinate=true-breedingtrue-breeding P generationP generation (parental generation) (parental generation)

11stst 2 individuals crossed 2 individuals crossed

Step 2:Cross-pollinated P Step 2:Cross-pollinated P generation generation

a. Purple flowers & white a. Purple flowers & white

b. Offspring=b. Offspring=FF11 generation generation

c. Recorded # of Fc. Recorded # of F11 plants expressing each plants expressing each traittrait

Step 3: FStep 3: F11 generation self-pollinated generation self-pollinated

a. Offspring of Fa. Offspring of F11 generation=F generation=F22 generationgeneration

b. Each Fb. Each F22 plant counted & recorded plant counted & recorded

1. White–flower w/purple–flowered yields:

F1 generation(first filial)

P generation purebred parents

all purple

Results of Mendel’s experiments

F1 generation hybrid offspring

¾ purple¼ white

2 purple–flowered offspring from F1 generation yields:

Data = 705 purple:224 whiteData = 705 purple:224 white

Reduced= Reduced=

705/224= 3.15= 705/224= 3.15=

3:1 ratio of purple to white 3:1 ratio of purple to white

VIII. In Review of 8-1VIII. In Review of 8-1

A.A. Mendel=“Father of Genetics” Mendel=“Father of Genetics”

B.B. Pea plant=small & easy to breed, Pea plant=small & easy to breed, good subject for studygood subject for study

C.C. Although he made amazing Although he made amazing discoveries in the world of discoveries in the world of genetics, his work went unnoticed genetics, his work went unnoticed for generations!for generations!