DNA

DNA Structure• DNA: Deoxyribonucleic acid• Each chromosome is made of one

piece of DNA46 chromosomes = 46 pieces of DNA

• DNA:– 2 strands connected– Shape of a twisted ladder– The twisted ladder is called a

DOUBLE HELIX

Function of DNA:

- Stores genetic information: genetic information makes you what you are

- Controls all cell and body activities

Chromosome Structure Section 12-2

Nucleotides: Basic building blocks of DNA

Nucleotides are made up of:

• Deoxyribose: a sugar

• Phosphate• Nitrogen Base:

– Adenine = A

– Guanine = G

– Cytosine = C

– Thymine = T

Nucleotides and Pairing: A-T C-G

The sugar and phosphate make the sides or rails of the double helix (ladder)

Structure of DNASection 12-1

DNA complementary strands

• The 2 strands of DNA are represented by the sequence of nitrogen bases

A T C G A A C G T T A

T A G C T T G C A A T

• Write the complementary DNA strand:

A T C G G G T T A A C G T A T C C

The People Behind

1. 1949: Erwin Chargaff discovers the rules of base pairing

A-T C-G

2. 1952: Rosalind Franklin determined that the DNA molecule was a coiled spiral.

They used a technique called X-ray diffraction

3. 1953: James Watson (USA) and Francis Crick (UK) determine the exact structure of DNA.

• Received the Nobel Prize in 1962

Nucleic Acids

• Are made of: C (carbon), H (hydrogen),

O (oxygen), N (nitrogen), P (phosphates).