Download What does DNA look like

What does DNA look like?
Inherited characteristics are determined by genes.
Genes are passed on to offspring
Genes are part of chromosomes
DNA = Deoxyribonucleic Acid
Pieces of the Puzzles
Material that make up genes have to be able to do two
things:
1. Give instructions to the cell for building and maintaining
2. Be able to be copied when the cell divides
Nucleotides: the Subunits of DNA
Nucleotides have three parts: sugar, phosphate and nitrogen
base
The sugar is deoxyribose
The nitrogen base is the nucleic acid part
There are FOUR nitrogen bases: Adenine (A), Thymine
(T), Guanine (G) and Cytosine (C)
FIGURE ONE p144.
Chargaff’s Rules
Erwin Chargaff found that the amount of adenine equals
the amount of thymine
And the amount of cytosine = the amount of guanine
Franklin’s Discovery
Rosalind Franklin took x-ray pictures of DNA and
determined that DNA has a spiral shape
Watson and Crick’s Model
Used Frankin’s data to help determine that DNA is like a
twisted ladder.
Built models of DNA
DNA’s Double Structure
Shape of DNA is known as a double helix
The two sides of the ladder are made of alternating sugars
and phosphates.
The steps or rungs of the ladder are made up of pairs of
nitrogen bases.
Chargaff’s data helped to show that A always pairs with T
and G always pairs with C on the DNA steps.
(Remember: I like to eat AT Golden Corral.)
FIGURE 4 page 146
Making copies of DNA
The base pairs allow the cell to copy or replicate the DNA.
Bases are complementary (A only pairs with T, C only
pairs with G).
How copies are made
1. The DNA molecule splits down the middle (unzips
down the center of each base pair step).
2. The bases on each side are a pattern to rebuild a new
complementary strand.
Two DNA strands are formed from one.
Each is made of half “old” DNA and half “new” DNA
When copies are made
Every time a cell divides, DNA gets copied.
Happens in interphase.
See page 147 FIGURE 5