April 27, 2010Ms. Simon Regents Biology

Introduction to Genetics

Do Now: 1) Identify some functions of proteinsMuscle, enzymes catalyze reactions, channels,

2) What does DNA stand for?Deoxyribose nucleic acid

3) Why is DNA important?Determines our traits“Hereditary material”

AIM: Does our hereditary material come from DNA or proteins?

Meischer (1869)

• Treated pus (white blood cells) with pepsin enzyme breaks down proteins (protease)

• Isolated the nuclei, precipitate is formed (DNA)

• nitrogen and phosphorous found in nuclein= material of the nucleus

Characteristics of hereditary material (DNA)

• Found in the nucleus

• Controls heredity (inherited traits)

• Self-replicating

• Change should result in change in organism

Griffiths Experiments• Studies pneumonococcus, bacteria that

causes pneumonia

• Two strains of the bacteria:

1) R-strain

2) S-strain

R-strain bacteria: rough, nonpathogenic, non-capsulated

S-strain: carbohydrate capsule that avoids the immune system and is pathogenic

1) Griffiths innoculates mice with S strain

Result: Mice dies

(Koch’s postulate)

2.Griffiths injects mice with R-strain bacteria

Results: Mice live

3) Heated the S strain and injected into the mice

Results: Mouselives

Why?

Material is denatured

4. Injected a mixture of heated S strain and normal R strain

Results: Mice died

Blood shows live S strain

• Genetic material was released from the S strain and taken up by the R strain to produce S strain bacteria

• The R strain had transformed into S strain

Pneumoniae cell extracts contain protein, DNA, and RNA.

How did scientists show that the transforming material was DNA?

Avery, MacLeod and McCarthy

1) Mix dead S and

Live R bacteria

2) Add protease

3) Add RNA-ase

4) Add DNA-ase

Transformation

• Assimilation of foreign DNA into own DNA

Conclusion: DNA is the hereditary material!

http://www.youtube.com/watch?v=9hzUjx_oD8E

Techno

http://www.youtube.com/watch?v=xXbyJNRwjlg