DNA – The Code for Life
Question: Why don’t we all
look alike?
All Living Things…
 Have cells.
 All cells contain the genetic instructions
that make an organism unique. 
Adapted to environment, appearance,
preferences, behaviors, survival instincts,
etc.
DNA
We get our
genetic codes
or instructions
from DNA that
is located
inside every
cell.
DNA
DNA stands for – Deoxyribonucleic acid
Functions of DNA:
1. Carries the codes to make
proteins.
2. Carries the genetic material
that is passed on from the
parents to the offspring.
Discovery of DNA
Rosalind Franklin - Invented X-ray diffraction
photography. Photo used
to determine the shape of
DNA is spiral.
DISCOVERY OF DNA
James Watson and Francis
Crick used the information
from Franklin and other
scientists to build a 3-D
model of DNA.
Won the
Nobel Peace
Prize in
Chemistry in
1961.
Structure of DNA
Shape of DNA - Like a twisted rope ladder.
This shape is called Double
Helix.
A single spiral would be
called Helix.
STRUCTURE OF DNA
Side Pieces (The Rope Part)
Are alternating units of
sugar and phosphate
groups. These go
down both sides of the
molecule
phosphate
Sugar (called deoxyribose)
STRUCTURE OF DNA
Nitrogen Bases (Steps of the ladder) 1.
2.
3.
4.
Adenine – A
Thymine – T
Cytosine – C
Guanine - G
The bases are
connected to the
sugar only !!!!!
STRUCTURE OF DNA
The nitrogen bases fit together in this way:
Adenine always goes
with Thymine
Cytosine always goes
with Guanine
phosphate
adenine
sugar
thymine
cytocine
guanine
STRUCTURE OF DNA
These three parts form the basic unit of DNA
called the NUCLEOTIDE. (subunits of DNA)
phosphate
Sugar
(deoxyribose)
Nitrogen base
Can be A, T, C or G
DNA Nucleotide Drawing
Where is DNA located?
 DNA molecules are coiled up inside of EVERY
SINGLE CELL!
 The structures that DNA is coiled into are called
CHROMOSOMES.  This is how the DNA molecules
actually fit inside of tiny cells.
CHROMOSOME ARRANGEMENT
All regular body cells have all the same parts in
multi-cellular organisms and the same # of
chromosomes.in human body
There are 46 chromosomes
cells; 23 pairs.
Chromosomes always come in pairs.
22 of the pairs are
similar.
The 23rd pair is
different.
These are the sex
chromosomes.
Male xy
NUMBERS OF CHROMOSOMES VS
COMPLEXITY
The number of chromosomes in the cells of eukaryotes differs
from one kind of organism to another and has NOTHING to do
with the complexity of the organism.
FOR EXAMPLE:
Goldfish - 98
Wheat - 42
Human - 46
Potato - 48
Fruit fly - 8
A fern called Ophioglossum reticulatum has 1,260
chromosomes per cell, more than any other known
Gene: segment of DNA on your
chromosomes that determines
your traits.
Traits
• Characteristics about an organism that are
determined by the information carried on
genes (segments of DNA).
How does DNA copy itself?
DNA copies itself to ensure that each new cell
that is produced gets the correct number of
chromosomes and receives an EXACT copy of
the DNA molecule.
This is called DNA REPLICATION.
The DNA molecule serves
as its own pattern or
template so as an exact
copy can be made.
DNA REPLICATION
What if there is a
mistake?
There is always a chance
that the wrong
nucleotide bonds to
another. HOWEVER,
DNA has a special
enzyme that is
responsible for “reading”
the bases and
recognizing and
replacing damaged or
wrong nucleotides. This
PROOFREADING
allows for only one (1)
error in ONE BILLION
nucleotides.
What happens when there is a
problem during replication?
 A permanent change in the sequence of DNA is
known as a mutation
 Not all mutations are bad.
Common mutations (in humans)
 Pimples/acne, high fertility (twins), heart disease,
diabetes, stroke, high blood pressure, color blindness,
heterochromia (two different colors in one eye OR two
different colored eyes), red hair, down syndrome, blue
eyes, freckles
DNA – The Code for Life Notes
All Living Things
Structure of DNA
•
•
•
Shape of DNA:
• Like a _____________________rope ladder.
• This shape is called double _____________.
•
Side Pieces (The Rope Part) - Are alternating units of
________________and phosphate groups. These go
down ____________sides of the molecule.
•
Nitrogen Bases ( The steps of the ladder)
• Adenine
• Thymine
• C__________________
• Guanine
•
The Nitrogen Base pairs fit together in this way:
Have ______________
All cells contain the __________________
instructions that make an organism unique.
DNA
•
•
•
We get our genetic codes or
___________________from _____________ that is
located inside every cell.
DNA stands for – Deoxyribonucleic ___________
Functions of DNA:
• Carries the codes to make ______________
• Carries the genetic material that is passed on
from the ___________________to the
offspring.
Discovery of DNA
•
Rosalind Franklin - Invented ___________
diffraction photography. Photo used to determine the
shape of DNA is ___________________,
•
James Watson and Francis Crick used the
information from Franklin and other scientists to
build a 3-D model of DNA.
•
Won the Noble Prize in Chemistry in 1961.
 Adenine always goes with Thymine
 Cytosine always goes with Guanine
Structure of DNA
•
These three parts form the basic unit of DNA called
the __________________ (subunits of DNA)
Chromosome Arrangement
• 22 of the pairs are ___________________, and
the 23rd pair is different
• The different chromosomes are the sex
chromosomes
• Male xy and Female ______
Where is DNA located?
•
•
DNA molecules are ___________ up inside of
EVERY SINGLE CELL!
The structures that DNA is coiled into are called
CHROMOSOMES  This is how the ___________
molecules fit inside of __________ cells.
Chromosome Arrangement
•
•
•
All ______________body cells have all the
same parts in multi-cellular organisms and the
same # of chromosomes.
There are _______chromosomes in human body
cells; 23 pairs.
_________________________ always come in pairs.
•
•
Gene – segment of _________ on your chromosomes
that determine your ___________
Traits - Characteristics about an _______________
that are determined by the information carried on
genes (segments of DNA).
How does DNA copy itself?
•
DNA copies itself to ensure that each new cell that is
produced gets the correct number of chromosomes and
receives an EXACT copy of the DNA molecule; this is
called DNA Replication.
What happens when there is a problem during
replication?
•
•
A permanent change in the sequence of DNA is known
as a mutation
Not all mutations are bad.