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A Quick Review!
•
What determines a proteins function?
•
Its shape.
•
What if you change its shape (by heating it for
example?
•
It stops working.
•
What determines the shape of a protein?
•
Its 1o structure or sequence of amino acids.
•
What happens if you change an amino acid in the
sequence of a particular protein?
•
It will fold slightly differently and not work properly (or at all!).
•
Why?
•
The side groups of the amino acids form bonds with each
other which results in 2o and 3o structure.
Our Guiding Question
• WHAT DETERMINES THE ORDER OF
AMINO ACIDS IN A PROTEIN???
DNA
(Deoxyribonucleic Acid)
What is DNA?
http://www.youtube.com/watch?v=
zwibgNGe4aY
Questions about DNA?
• What does DNA look like?
• How is DNA made?
• How do we know DNA has the instructions
to make proteins?
• How does DNA instruct the cell to make
proteins?
DNA is universal to life
• All living organisms have DNA
– Bacteria, fungi, plants, animals…and even
many viruses
• The function of DNA is to store information
for an organism’s characteristics
The nucleus stores DNA in
eukaryotic cells
human cheek
cell
Elodea leaf cell
mitochondria
chloroplasts
vacuole
nucleus
(DNA here)
(DNA here)
Prokaryote cells do not have a nucleus
but DO have DNA
E. coli bacteria cell
DNA
In the cell, DNA forms structures
called chromosomes
• A eukaryotic chromosome is typically a
very long, single chain of DNA
In the cell, DNA forms structures
called chromosomes
• A prokaryotic chromosome is typically a
circular chain of DNA
– Prokaryotic cells also often have smaller
circles of DNA called plasmids
E. coli bacteria cell
Chromosome DNA
Plasmid DNA
What does DNA look like?
• We will begin our investigation into DNA
by looking at its structure.
DNA is a double helix
• The shape of a DNA molecule is like a
twisted ladder or spiral staircase
DNA is a polymer made of
monomers called nucleotides
• A nucleotide has 3 parts: a phosphate, a
sugar, and a base.
PHOSPHATE
BASE
SUGAR
There are 4 DNA nucleotides
• They are the same except for their bases
Adenine
Thymine
Cytosine
Guanine
Making a DNA molecule
1. One strand of
a DNA
molecule is
formed by
linking
together the
sugars and
phosphates of
nucleotides.
Hydrogen bonds
2. The two strands
(halves) of a DNA
molecule are
connected by
hydrogen bonds
between the
bases of
nucleotides.
Hydrogen bonds
Complementary base pairing
• In DNA molecules…
Adenine only bonds to thymine.
Cytosine only bonds to guanine.
A—T
G—C
DNA Structure
Your goals:
1. Build the 4 different Nucleotides by your
self
2. Take 2 of your Nucleotides (whichever
you would like) and add it to the class
DNA molecule
3. We will use the other Nucleotides in the
second part of class