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Goals:
• Gene Regulation in Eukaryotes– Regulation at the DNA Level– Regulation at the transcription level– Regulation at the translation level– Regulation at the protein level
– How might regulation change the function of a stem cell? Cause a cell to become cancerous?
Alternative Splicing• One gene = many
proteins• Original
hypothesis (Beadle and Tatum)=one gene; one enzyme
• Intron: intervening
• Exon: expressed
Cap and Tail• The RNA transcript must be protected from
DNAses in the cytoplasm!– 5’ GTP cap: protects the end and helps the RNA
bind to the ribosome– 3’ polyA tail: protects the end and allows RNA to
go tail first out of the nucleus
Control of Translation
• RNAi:– Triggered by siRNA’s• dsRNA is chopped up by “dicer”
– Can do two things:• Degrade RNA
– RISC complex leads to chopping up of mRNA
• Block Translation– RISC complex leads to hairpin shape that blocks translation by
ribosome.
Further research
• NOVA video: (accelerated biology level)– NOVA, RNAi– http://video.pbs.org/video/1506740590/
• Pdf review from Nature: Available on my website (college level).
Regulation of Gene Expression at the Protein Level
• Activation or inhibition of proteins– Can the timing of when a protein is expressed be
altered? Even if it is present the whole time?– Have we seen this already this year?– Many proteins functon as complexes working
together.• P53 is often one a few transcription factors needed to
activate transcription. Without its “friends” p53 activity is downregulated