1. Regulatory RNAs

2. RNA DNA mRNA rRNA tRNA snRNA snoRNAmicroRNA siRNAribozymes Protein synthesis Splicing of mRNA Processing of rRNA Regulation of gene expression Catalysts

3. Whole genome studies Tiling assays

4. Bacterial sRNAs bind to mRNAs and trigger degradation or regulate translation

5. Riboswitches and attenuation are mechanisms to control gene expression in bacteria Organization of a riboswitch

6. Example: a SAM riboswitch Termination of transcriptionRepression of translation initiation

7. Example: a SAM riboswitch Transcriptional terminator

8. Examples of riboswitches and their metabolites

9. Attenuation is used in bacteria to regulate transcription of biosynthetic genes The leader peptide contains trp amino acids

10. Attenuation is used in bacteria to regulate transcription of biosynthetic genes

11. Bacterial defense against viruses: The CRISPR system CRISPR: Clustered Regularly Interspaced Short Palindromic Repeats Organization of a CRISPR locus

12. Organization of CRISPR-associated genes in bacteria CRISPR locus

13. Acquisition of spacer sequences PAM: protospacer adjacent motif

15. Processing of CRISPR RNA and its antiviral action E.coliP. furiosus

18. Gene-editing using the CRISPR-Cas9 system Animation Animation1

19. RNA DNA mRNA rRNA tRNA snRNA snoRNAmicroRNA siRNA piRNAs ribozymes Protein synthesis Splicing of mRNA Processing of rRNA Regulation of gene expression Catalysts

20. In eukaryotes short RNAs are generated by mechanisms that are different from the mechanisms that generate sRNAs in bacteria. RISC: RNA-induced silencing complex Bacterial sRNAs are encoded by small genes whereas eukaryotic small RNAs are processed from longer transcripts.

21. The PIWI-interacting RNA (piRNA) system is thought to silence transposons by passively acquiring and expressing transposon sequences

22. Processing and function of microRNAs and siRNAs RISC: RNA-induced silencing complex

23. Pre-microRNAs can originate from various regions of a primary transcript (pri-miRNA)

24. Structures of pre-microRNAs in Caenorhabditis

25. General structure of a pri-microRNA and its processing sites

26. Processing of pri-microRNAs by Drosha in the nucleus Microprocessor complex Pasha, Pre-miRNA (F2) is transported into the cytoplasm

27. Dicer processes microRNAs in the cytoplasm PAZ: PIWI, argonaute, zwille

28. General structure of a pri-microRNA and its processing sites

29. Argonaute (as part of a RISC complex) cleaves mRNAs after complementary base pairing of its guide RNA.

30. In eukaryotes short RNAs are generated by different mechanisms than sRNAs in bacteria RISC: RNA-induced silencing complex

31. Centromeric silencing in S. pombe involves RNAi

32. Short interfering RNAs can be copied by an RNA- dependent RNA polymerase to amplify the inhibitory effect

33. Repressing gene expression by RNAi in Caenorhabditis

34. X-chromosome inactivation is initiated by expression of the Xist gene from the X-chromosome inactivation center (Xic) Xist: X-inactive specific transcript Long non-coding RNAs (lncRNAs), longer than 200 nucleotides Regulatory elements

35. Visualizing the Xist lncRNA (a) and the acetylation state of one of the X-chromosomes (b)

36. Calico cats have patch-colored fur due to expression of different X-chromosome alleles