http://www.ornl.gov/hgmis

Gene Expression Defines Cells

Recall the Central Dogma

DNA RNA PROTEINInfo Info Carrier Functional Product

http://www.ornl.gov/hgmis

All Information is in DNA

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

DNA is a Nucleic Acid

Three components Nitrogenous Base (A, C, G, T) Ribose Sugar Phosphate

Nucleotides in DNA

Nucleotide Bases

Nucleotide Detail

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)

DNA and RNA

Phosphodiester Links Nucleotides

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

Complementary Base Pairing

DNA Structure

DNA Structure Reveals Copying Mechanism

DNA is Transcribed

http://commons.wikimedia.org/wiki/Image:DNA_transcription.gif

Transcription Initiation

http://upload.wikimedia.org/wikipedia/commons/thumb/9/91/Simple_transcription_initiation1.svg/721px-Simple_transcription_initiation1.svg.png

Promoter with Transcription Factors

http://stemcells.nih.gov/StaticResources/info/scireport/images/figurea6.jpg

Transcription and Translation

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 -NH3 and -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 Each codon specifies an amino

acid

Triplet codons are decoded by tRNA 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>.

http://www.ornl.gov/hgmis

Overview of Gene Expression