1. The Central Dogma DNA  RNA  Protein  Function Replication
Transcription
Replication
Translation
Work

2. The cell as a factory
DNA = Complete instructions for making and maintaining the product. (How to put together “Dave” and keep him running).
Has to be kept safe and accurate.
Has to be kept organized.
RNA = Portable copy of one part of the instructions. (Photocopy to run down to the factory floor.
Also called “messenger” RNA or “mRNA”.
Just made when it’s needed and then it’s disposable.
Protein = Tools and materials used for actually building the product.
“Enzymes” are proteins that act as machinery to make something the cell needs.
“Structural proteins” are proteins used to form the structure of the cell. (like lumber and nails)

4. Getting from the instructions to the product

5. Only one strand of DNA serves as a template for making the RNA (transcription).
Different genes are transcribed from different strands

6. Transcription
Catalyzed by RNA polymerase – a complex, multisubunit enzyme that catalyzes the formation of the phosphodiester bonds that link together the nucleotides in an RNA chain

7. Transcription- making the mRNA Translation- making the protein
Transcription start site
Transcription
Off to work!
Protein
Ribosome 3’
mRNA 5’
AUG TTA GCG CCT ATC TAA
Translation start site
Translation stop site
Gene Structure

8. Promoters
RNA polymerase must bind at the promoter to start making the mRNA (transcription).
Other proteins must bind to the promoter to regulate when the RNA polymerase is supposed to make the mRNA.
~200 bp
gene

9. Promoters regulate gene expression
The Promoter determines:
Which DNA strand will serve as a template.
When to start making the mRNA.
Where to start making the mRNA (Transcription starting point ).
When to stop making the mRNA (How much to make).

10. Bacterial Gene Structure
Bacterial (prokaryotic) genes
One mRNA can contain several coding regions (ORFs).
Each ORF has it’s own translation start and stop
transcription
Gene 1
Gene 3
Gene 2
promoter
DNA with one promoter controlling several genes
mRNA containing several genes
start
stop
start
stop
start
stop

11. Prokaryotic Gene Expression
DNA:
Promoter
Cistron1
Cistron2
Cistron3
Terminator
Transcription
mRNA: 5’ 3’
ORFs: 1 2 3
Translation N N C N
Proteins: C C 1 2 3

12. Plant and Animal Gene Structure
Plant and animal (Eukaryotic) genes
One mRNA contains a single coding region (ORF).
Gene
promoter
transcription
DNA with one promoter controlling one gene
mRNA containing a single ORF (gene).
start
stop

13. Introns: Plant and Animal Genes Often Contain “Extra” DNA
The coding region in some Eukaryotic genes is interrupted by non-coding regions that have to be removed before the protein is made.
The ORFs in the gene are called ”Exons”
The extra DNA chunks are called “Introns”
The “pre-RNA” also contains the sequence information that tell the cell where to trim out the “extra” DNA (splice junctions).
“Processed” mRNA has the normal translation starts and stops needed to make the protein.

14. From Gene to Protein

15. Bioinformatics
We’re getting REALLY good at sequencing DNA and sequence databases now contain around a bazillion jillion bases from a plethora of critters.
“Mining” for useful information in that glut of information is what bioinformatics is about.
Bioinformatics is basically the application of some rules and strategies for finding genes.
Fortunately, the rules aren’t all that hard.

16. Steps to finding genes Find ORFs
This is the biggest target, easiest to find- look for long stretches of triplet codons that don’t have a stop codon.
Find the “Start” Codon (where the protein begins)
Always an ATG (Methionine codon)
Usually quite near the beginning of the ORF (5’ end)
Find Promoter Elements (TATA and CAAT boxes)
Should be before an ORF, (also referred to as “upstream” or 5’ of an ORF).
May have ambiguous sequence. (TATA box may look like “TATAA” or “TAATA” or “TATATA” or “TTATAA”).

17. LUNCH TIME !!!!!!