1. Gene Structure

2. Topics to be Covered Introduction Gene structure Promoter Terminator
Splice site

3. Terminology Genome – entire genetic material of an individual
Transcriptome – set of transcribed sequences
Proteome – set of proteins encoded by the genome

4. Terminology
Only one strand of DNA serves as a template for transcription.
Different genes are transcribed from different strands

5. From Gene to Protein

6. Eukaryotic Gene Structure
5’ - Promoter Exon Intron Exon Terminator – 3’
UTR splice splice UTR
transcription
Poly A
translation
protein

7. Prokaryotic Gene Structure
Promoter CDS Terminator
UTR UTR
Genomic DNA
transcription
mRNA
translation
protein

8. Topics to be Covered Introduction Gene structure Promoter Terminator
Splice sites

9. Promoter Promoter determines: Which strand will serve as a template.
Transcription starting point.
Strength of polymerase binding.
Frequency of polymerase binding.

10. Prokaryotic Promoter One type of RNA polymerase.
Pribnow box located at –10 (6-7bp)
–35 sequence located at -35 (6bp)

11. Eukaryote Promoter
3 types of RNA polymerases are employed in transcription of genes:
RNA polymerase I transcribes rRNA
RNA polymerase II transcribes all genes coding for polypeptides
RNA polymerase III transcribes small cytoplasmatic RNA, such as tRNA.

12. Eukaryote Promoter Goldberg-Hogness or TATA located at –30
Additional regions at –100 and at –200
Possible distant regions acting as enhancers or silencers (even more than 50 kb).

13. Promoter Promoters sequences can vary tremendously.
RNA polymerase recognizes hundreds of different promoters

14. Promoter Strong promoter resemble the consensus sequence.
Mutations at promoter sites can influence transcription.
Human gene Beta globin

15. Promoter Conclusions: Promoters are very hard to predict.
Promoter prediction must be organism-dependent (and even polymerase-dependent).

16. Termination Sites
The newly synthesized mRNA forms a stem and loop structure (lollipop).
A disassociation signal at the end of the gene that stops elongating and releases RNA polymerase.
All terminators (eukaryotes and prokaryotes) form a secondary structure.

17. Termination Sites
The terminator region pauses the polymerase and causes disassociation.

18. Splice Sites Eukaryotics only
Removing internal parts of the newly transcribed RNA.
Takes place in the cell nucleus (hnRNA)

19. Splice Sites
Conserved splice sites are shared by both the exon and the intron.
Different signals on the donor site (3’) and on the acceptor site (5’).

20. Splice Sites

21. Alternative splicing
Different splice patterns from the same hnRNA sequence. Different products from the same gene
Different organs, different stages of development in the same cell.
Exact splice sites are difficult to predict