What Does DNA Look Like

1
What Does DNA Look Like?

• 6.1

2
The Pieces of the Puzzle

• Inherited characteristics are determined by genes
• Genes are passed from one generation to the next
• Genes are parts of chromosomes
• Chromosomes are structures in the nucleus made of
  DNA and protein

3
DNA

• Deoxyribonucleic Acid
• A molecule that is present in all living cells
  and that contains the information that determines
  the traits that a living thing inherits and needs
  to live
• Must be able to give instructions for building
  and maintaining cells
• Must be able to be copied each time a cell divides

4
Nucleotides

• In a nucleic-acid chain, a subunit that consists
  of a sugar, phosphate, nitrogenous base
• Identical except for the base
• Adenine Thymine
• Guanine Cytosine
• Each has a different shape

5
Chargaffs Rules

• 1950s Erwin Chargaff found that the amount of
  Adenine in DNA equals the amount of Thymine, and
  the amount of Guanine equals the amount of
  Cytosine

6
Franklins Discovery

• Rosalind Franklin made images of DNA molecules
• Used X-Ray Diffraction
• X rays are aimed at the DNA molecules
• When an X ray hits part of the molecule it
  bounces off
• The rays bouncing off are capture on film
• Found DNA to be in a spiral shape

7
Watson and Crick

• James Watson and Francis Crick
• Looked at Franklins X Ray images, and concluded
  that DNA was like a ladder

8
DNAs Double Structure

• Double Helix looks like a twisted ladder
• Two sides made of alternating sugar and
  phosphates
• Rungs of the ladder are made of base nucleotides.
  

9
Making Copies of DNA

• Replicate make copies of DNA
• Each base always bonds with only one other base
• Complimentary Bases
• CGTATCC GCATAGG

10
How Copies Are Made

• DNA molecules is split down the middle (where the
  bases meet)
• The bases on each side are used as a pattern for
  a new strand
• 2 DNA molecules are formed
• Half old, half new

11
When Copies Are Made

• DNA is copied EVERY time a cell divides
• Unwinding, copying, re-winding is done by proteins