Criteria for Hereditary Material

1) Found in nucleus

2) Arranged into chromosomes

3) Can control heredity

4) Self-replicating

How did scientists show that the transforming material was DNA?

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

Conclusion: DNA is the hereditary material!

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

Techno

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

April 29, 2010Ms. Simon Regents Biology

• Do Now: Turn in Lab Activity

• How did Griffiths show that bacteriophage DNA can “transform”?

DNA

• Stored in the nucleus as chromosomes

• Each chromosome is a long strand of DNA

• Chromosomes are coiled using histones (proteins)

What is the structure of DNA?

DNA= Deoxyribose nucleic acid

The monomers of DNA are nucleotides

• Each nucleotide contains:

1) phosphate (PO4) backbone

2) deoxyribose (5 Carbon sugar)

3) nitrogenous base

Nitrogenous Bases

Purines have two rings

Pyrimidines have one

ring

Chargoff analyzed DNA of different species

# Adenine= # Thymine# Guanine= #Cytosine

Hypothesis: Maybe A is bound to T and G is bound to C

Rosalind Franklin• X-ray diffraction technique- allows her to

take pictures of DNA’s structure

• Helix shape

Watson and Crick

• Won the Noble Prize for discovering the structure of DNA

• Model of DNA is a double helix, two strands are wound around each other

Double-helix model

Ribose and Phosphate

on the outside

Nitrogenous bases pair

as “rungs” of the ladder

equidistant

Nitrogenous bases are bound through weak hydrogen bonds

Phosphates and riboses are covalently bonded

• Adenine and Thymine= 2 hydrogen bonds

• Guanine and cytosine= 3 hydrogen bonds

Template Strand

C T A G T T A C A

G A T C A A T G T

Complementary Strand

During DNA replication, DNA molecule separates into two

strands.

Two new complementary strands are formed.

Replication is carried out by enzymes that unzip DNA molecule

Helicase- enzyme that unwinds DNA

DNA Polymerase

• DNA polymerase forms the new strand of DNA