Gene Expression Defines Cells
http://www.ornl.gov/hgmis
Recall the Central Dogma
Info
DNA
Info Carrier
RNA
Functional Product
PROTEIN
All Information is in DNA
http://www.ornl.gov/hgmis
DNA is a Nucleic Acid
Principle information molecules in the cell
Linear polymer of nucleotides (or bases)
Two types

Deoxyribonucleic Acid – DNA


Information storage in cells
Ribonucleic Acid – RNA

Information carrier in cells
Nucleotides in DNA
Three components
Nitrogenous Base (A, C, G, T)
 Ribose Sugar
 Phosphate

Nucleotide Bases
Nucleotide Detail
DNA and RNA
For DNA bases are A, C, G, T

Sugar is deoxyribose (no OH at 2’ position)
For RNA bases are A, C, G. U

Sugar is ribose (OH at 2’ position)
Phosphodiester Links Nucleotides
Complementary Base Pairing
Holds nucleic acid strands together
H-bonding between complementary bases

This is an interaction that is easily broken
A pairs with T (DNA), (A-U for RNA)
G pairs with C (both DNA and RNA)
Complementary Base Pairing
DNA Structure
DNA Structure Reveals Copying
Mechanism
DNA is Transcribed
http://commons.wikimedia.org/wiki/Image:DNA_transcription.gif
Transcription Initiation
Promoter with Transcription Factors
http://upload.wikimedia.org/wikipedia/commons/thumb/9/91/Simple_tr
anscription_initiation1.svg/721pxSimple_transcription_initiation1.svg.png
Transcription and Translation
http://stemcells.nih.gov/StaticResources/info/scireport/images/figurea6.jpg
Proteins
Primary functional molecules of the cell; execute
the tasks directed by the genetic material
1.
Structural molecules (e.g., hair, fingernails, connective tissue)
2.
Transmitting Information between cells (e.g., hormones)
3.
Defense against infection (e.g., antibodies)
4.
Enzymes (catalyze nearly all biochemical reactions)
Building Blocks are Amino Acids
20 different amino acids in proteins
Chemical properties of side chains determine function
Central carbon atom (Ca)
1. H atom
2. Amino group (NH3+)
3. Carboxyl group
(COO-)
4. R group (side chain)
R-group (Side Chain)
R -group determines identity, function
A.A. are categorized by chemical properties of the side
chains
1) Polar (uncharged) = hydrophilic
2) Positively charged (basic) = ionic
3) Negatively charged (acidic) = ionic
4) Nonpolar = hydrophobic
Nonpolar Amino Acids
The side chains of these a.a. tend to be located in the interior of proteins, where they are not
in contact with water.
Peptide Bond
Links amino acids
Amide linkage
between a-NH3 and
a-COO
Defines amino (N)
terminus and
carboxy (C)
terminus
Protein Structure
Polypeptide (protein)
chains fold into globular
structure
Defines cracks and
crevices that can interact
with other molecules
Allows proteins to be
enzymes
Enzymes
Enzymes are catalysts
They increase the rate of reactions
This allows rapid synthesis and degradation
of products in cells
Building Proteins -Translation

mRNA contains 3 nucleotide
codons


Triplet codons are decoded by
tRNA


Each codon specifies an amino
acid
decoding is base pairing between
codon on mRNA and anticodon
on tRNA
Each tRNA carries a specific
amino acid

codon-anticodon pairing delivers
specific aa to the growing
polypeptide chain
"protein: synthesis." Online Art. Britannica Student Encyclopædia.
10 Aug. 2008 <http://student.britannica.com/eb/art-1692>.
Overview of Gene Expression
http://www.ornl.gov/hgmis