Cell Biology Lecture #19 notes p.401-424 Control of Gene Expression

DNA= "Instruction manual for making a human"? Proteomics: Second half of the genetic code

Selective gene expression makes cells different in the same organism

Adult nucleus into enucleated frog egg produces a normal tadpole like the nuclear donor. Similar plant cloning results

Some proteins are present in all cells, while other proteins are only present in certain differentiated cells

External signals influence gene expression; note significance of caloric restriction data!

Control points; whatever works! 1.Transcription 2.RNA processing 3.RNA transport 4.Translation 5. RNAdegradation 6. Posttranslational control #1 most important

Turning genes on and off determined by DNA sequences and binding of regulatory proteins

classic models: lambda, lac,trp operons. CAP (energy charge), cro(lytic cycle), CI (lambda repressor; lysogenic state) trp repressor (+ trp; shut off biosynthesis) all helix-turn-helix

Helix NOT opened, major groove's geometry determined by base sequence, minor groove not

20 weak contacts = strong and specific binding of DNA and regulatory protein

Homeotic selector genes: halteres = second set of wings (single mutation)!

Homeodomain; 60 amino acid patch almost identical in fruit fly and mouse!

Yeast homeodomain sequence homology much less; DNA binding almost identical (conserved)

Zinc fingers (polypeptides + zinc), leucine zipper (clothespin),helix-loop-helix (inactivatable)

Gel mobility shift assay to purify binding proteins.

DNA affinity chromatography + reverse translation + PCR = lots of regulatory protein's gene

Trp operon (C. Yanofsky)

Positive and negative controls

Eucaryotes: Much more complex. DNA = physical entity for "crack the whip"