Download s - Biology: 3 Overview

E.Q. – Identify the base pair
rules and explain the process
of DNA Replication.
12.1/2 Notes
Pg. 58
Discovery of DNA
 Watson and Crick build
a model of the DNA
double helix. 1953
 X-ray diffraction (photo
51) was used to
determine the double
helix shape.
 Rosalind Franklin
function and structure of DNA
Function: To store & transmit genetic information
Structure: Double helix made of nucleotides (3 parts)
1. 5-carbon sugar
2. Phosphate
3. Base
• Phosphate & sugar make up backbone of ladder.
•Base pairs make up rungs of ladder
There are 4 bases in DNA
Bases:
Purines
Adenine
Guanine
Pyrimidines
Thymine
Cytosine
hydrogen bonds
The 4 bases in DNA
Guanine
Bases always pair together

Adenine (A) pairs with
Thymine (T)
• Double hydrogen
bond

Guanine (G) pairs with
Cytosine (C)
• Triple Hydrogen
bond
 Good Company is
Always Together
DNA replicates itself
 Must happen before a cell divides (Mitosis)
 During S phase of Interphase
 Results in two exact copies of DNA
DNA Replication (semi-conservative)
1. Helicase enzyme unzips
DNA
2. DNA Polymerase attaches
complementary base pairs
DNA =
NEW CHAIN=
A-T-T-C-C-G
T-A-A-G-G-C
3. Each DNA molecule has 1/2
old & 1/2 new
4. Semi-conservative
Replication
DNA replicates itself
12.1, 12.2 review
1. Draw a nucleotide pg. 329. What 3 parts make
up a nucleotide? What part(s) make up the
rungs? What part(s) make up the backbone?
2. What are the base pair rules?
3. Explain semiconservative replication.
(draw picture to help explain—use colors)
4. Match the complementary base pairs to the
following. A-T-T-G-A-C-G-G
5. Describe the role of DNA helicase, and DNA
polymerase in DNA replication.