1. CHMI 2227E Biochemistry I Gene expression
CHMI E.R. Gauthier, Ph.D.

2. Nature of the gene
CHMI E.R. Gauthier, Ph.D.

3. Species Genome size Number of genes Humans 2.9 billion base pairs
20,000-25,000
Drosophila (Drosophila melanogaster)            
120 million base pairs
13,601
Yeast
(Saccharomyces cerevisiae)            
12 million base pairs
6, 275
Nematode (Caenorhabditis elegans)            
97 million base pairs
19,000
E. coli            
4.1 million base pairs
4,800
Arabidopsis (Arabidopsis thaliana)            
125 million base pairs
25,000
CHMI E.R. Gauthier, Ph.D.

4. Nature of the gene
CHMI E.R. Gauthier, Ph.D.

5. Nature of the gene
CHMI E.R. Gauthier, Ph.D.

6. What happens when gene expression is screwed-up?
Antennapedia
mutation
Normal
fly
CHMI E.R. Gauthier, Ph.D.

7. Central dogma of molecular biology
CHMI E.R. Gauthier, Ph.D.

8. Transcription: turning on a gene
Promoter
Transcription
factors
CHMI E.R. Gauthier, Ph.D.

9. Promoters
CHMI E.R. Gauthier, Ph.D.

10. Promoters
CHMI E.R. Gauthier, Ph.D.

11. Transcription
CHMI E.R. Gauthier, Ph.D.

12. Messenger RNA (mRNA) is antiparallel to template strand
Transcription
Messenger RNA (mRNA) is antiparallel to template strand
Complementarity
(5’ 3’)
CHMI E.R. Gauthier, Ph.D.

13. mRNAs are modified in eukaryotes
CHMI E.R. Gauthier, Ph.D.

14. mRNAs are modified in eukaryotes
CHMI E.R. Gauthier, Ph.D.

15. mRNAs are translated into proteins
CHMI E.R. Gauthier, Ph.D.

16. Translation
CHMI E.R. Gauthier, Ph.D.

17. Transfer RNA (tRNA)
CHMI E.R. Gauthier, Ph.D.

18. The genetic code 5’ 3’ A U
mRNA
CHMI E.R. Gauthier, Ph.D.

19. The genetic code
CHMI E.R. Gauthier, Ph.D.

20. Translation
CHMI E.R. Gauthier, Ph.D.

21. Translation - Initiation
The initiation codon is ALWAYS AUG  Methionine
fMET = N-formyl methionine
CHMI E.R. Gauthier, Ph.D.

22. Translation - Elongation
Peptide bond: synthesized by the « peptidyl transferase »
enzyme on the large ribosomal subunit
Translocation
CHMI E.R. Gauthier, Ph.D.

23. Translation - Termination
Three « Stop » codons exist: UGA; UAA, UAG
CHMI E.R. Gauthier, Ph.D.

24. Change in cell behavior
Protein folding
Change in cell behavior
Change in organism
Adaptation to
environment
Cue from environment (hormones, temperature, etc)
Protein function
CHMI E.R. Gauthier, Ph.D.