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DNA
STUDENTS WILL:
• Identify the parts of a DNA
molecule and its structure.
• Explain how DNA copies itself.
• Describe the structure and
function of each kind of RNA.
Vocabulary:
• DNA
(Deoxyribonucleic Acid)
• RNA
(Ribonucleic Acid)
• Gene
• Mutation
DNA stands for:
D: Deoxyribose
N: Nucleic
A: Acid
DNA is too
small to see,
but under a
microscope
it looks like
a twisted up
ladder!
Every living thing has DNA. That means that
you have something in common with a zebra,
a tree, a mushroom and a beetle!!!!
What is DNA?
• A chemical code used by the
cell
• Contains GENETIC information
important for cell growth and
function.
•
HISTORY OF
DNA
A. Rosalind Franklin
X-ray photo of DNA.
(1952)
B. Maurice WilkinsX ray pattern of DNA
C. Watson and Crick
- described the DNA molecule
from Franklin’s X-ray.
(1953)
Watson and Crick: 3-D model of
DNA
Nobel Prize for 3-D model of DNA
DNA
STRUCTUR • 2 chains molecules in a
spiral form
E:
-
• Shaped like a spiral
staircase or a twisted
ladder 
DNA
• Steps of the ladder
STRUCTURE (rungs) are made up
of pairs of nitrogen
bases
• Sides of the ladder
are made up of Sugar
Phosphates
DNA Double Helix
“Rungs of ladder”
Nitrogenous
Base (A,T,G or C)
“Legs of ladder”
Phosphate &
Sugar Backbone
Watson & Crick
proposed…
• DNA had specific pairing between the
nitrogen bases:
• ADENINE (A) – THYMINE (T)
• CYTOSINE (C) –GUANINE (G)
• DNA was made of 2 long stands of
nucleotides arranged in a specific
way
called the “Complementary
Rule”
Rosalind Franklin’s DNA image
“Chargaff’s rule”
A=T & C=G
BASEPAIRINGS
H-bonds
G
C
T
A
Genetic Diversity…
-Different
arrangements of
NUCLEOTIDES in a
nucleic acid (DNA)
provides the key to
DIVERSITY among living
organisms.
Life…
The “code” of the chromosome is the
SPECIFIC ORDER that bases occur.
A T C G T A T G C G G…
DNA is wrapped tightly around
histones and coiled tightly to form
chromosomes
ACTCATGGTCATG
TGAGTACCAGTAC
Note:
THIS IS AN EXAMPLE OF A GENETIC CODE
THAT MAY BE FOUND IN YOUR BODY.
EXAMPLE:
ATCGTCAGG MAY BE FOR HAIR COLOR.
BUT
ATCGTCAGC MAY BE FOR EYE COLOR
DNA Replication
• DNA-copied =
identical DNAs
• When? Interphase
• Steps:
1. Enzyme (helicase)
unzips the DNA
strand.
2. New bases pair
with bases on
original DNA
3. 2 new identical
DNA are produced.
GENES?
• A section of DNA
that contains
instructions for making
PROTEINS
What are Proteins?
Proteins (amino acids)
build tissues and cells
or work as enzymes
How are
PROTEINS
made?
RNA (Ribonulceic acid)
- Made inside DNA (
TRANSCRIPTION)
- 4 Bases:
- Adenine (A)
- Guanine (G)
- Cytosine (C)
- Uracil (U)
-Sugar (Ribose)
-3 Main Kinds
m (RNA)
messenger
r (RNA)
Ribosomal
t (RNA)
Transfer RNA
m (RNA) – carries the DNA code to the
ribosomes
r (RNA) – makes up part of the Ribosomes
t (RNA) – bring amino acids to the ribosomes to
be assembled into proteins
DNA
Transcriptio
n
-DNA can
“unzip” itself
and RNA
nucleotides
match up to the
DNA strand.
-Both DNA &
RNA are formed
from
NUCLEOTIDES
and are called
TRANSLATION
- PROCESS WHERE
THE RIBOSOMES
SYNTHESIZE
PROTEINS WITH
THE HELP OF
mRNA
DNA vs RNA
DNA
RNA
• Deoxyribonucleic acid
• Found in nucleus
• Ribonucleic acid
• Found in nucleus and
cytoplasm
• Bases are A,G,C,U
• More resistant to
damage by ultra-violet
rays.
• Single stranded
molecule
• Bases are A,G,T,C
• Can be damaged by
exposure to ultra
violet rays.
• Double-stranded
molecule
Continue…
DNA
RNA
• A-T, G-C
• A-U, G-C
• Contain the genetic • Responsible for
instruction used in
making proteins
the development
and functioning of
all cells
Mutation
?
-A change in
the sequence
of DNA that
codes for a
gene or a
change in the
number of
chromosome.
What cause Mutation?
X-ray
Sunlight
Chemicals
Results of Mutation:
Harmful
Beneficial
Neutral
AMAZING DNA FACTS…
-DNA from a single
human cell extends in a
single thread for almost
2 meters long!!!
-It contains information
equal to some 600,000
printed pages of 500
words each!!!
(a library of about 1,000
books)