Transcript DNA - Midway ISD

 Where do we get our DNA from?
Structure of DNA
 Discovered in 1950s by Rosalind Franklin
using X-ray diffraction.
 “Double Helix” term coined by Watson and
Crick in the 1950s as well.
 DNA is arranged into a ladder-like structure
called a Double Helix.
DNA Structure
 A molecule of DNA is made up of millions of
tiny subunits called Nucleotides.
 Each nucleotide consists of:
1. Phosphate group
2. Pentose sugar
3. Nitrogenous base
Nucleotides
Phosphate
Nitrogenous
Base
Pentose
Sugar
Nucleotides
 The phosphate and sugar form the backbone
of the DNA molecule, whereas the bases form
the “rungs”.
 There are four types of nitrogenous bases.
Nucleotides (Practice)
A
Adenine
(Purine)
C
Cytosine
(Pyrimidines)
T
Thymine
(Pyrimidines)
G
Guanine
(Purine)
Nucleotides
 Each base will only bond with one other
specific base.
 Adenine (A)
 Thymine (T)
 Cytosine (C)
 Guanine (G)
Form a base pair.
Form a base pair.
DNA Structure
 Because of this complementary base pairing,
the order of the bases in one strand determines
the order of the bases in the other strand.
BASE PAIRING IS ALWAYS EQUAL!!!!
(Ex: 25% A=25% T)
A
T
C
G
T
A
C
G
A
T
G
C
T
A
What do these have in common?
ALL organisms have the
SAME components that
make up their DNA!
Think about the
Alphabet...
DNA Structure
 A gene is a section of DNA that codes for a
protein.
 Each unique gene has a unique sequence of
bases.
 This unique sequence of bases will code for the
production of a unique protein.
 It is these proteins and combination of proteins
that give us a unique phenotype.
DNA
Gene
Protein
Trait
The purpose of DNA is to help the
ribosomes make PROTEIN!!!!
Write this down..
How are our traits
carried on our DNA?
 DNA is copied during a process called
replication!
 What phase of the cell cycle does DNA
replication occur?
 Replication results=one new strand & one
original strand
 http://www.youtube.com/watch?v=5_vzY7H
9GYk&feature=related