Gene Regulation Bacteria respond to environment Must produce or absorb essential molecules Turn on genes when environment is lacking target molecule Turn off genes to save resources when target molecule is in environment DNA RNA Protein Regulation strategies: Tryptophan Control enzyme activity Feedback inhibition Positive or negative? Control production of enzymes Operon model Turns genes on and off, controls RNA production lactase Operons Operator- switches on a group of adjacent genes Repressor- binds to operator and prevents transcription Repressor is reusable, can attach and detach from operator Repressible Operons- usually on Tryptophan activates repressor Repressor binds to operator Gene inactivated Tryptophan can come from either environment or rom synthesis Inducible operon- usually off Lactose inactivates repressor Repressor drops off DNA Enzymes are transcribed Once lactose is gone repressor binds again Metabolic pathways Repressible enzymes anabolic pathways Build up larger molecules Once end product is present pathway turns off Inducible enzymes catabolic pathways Break down larger molecules Turn on in the presence of starting product Eukaryotic, multicellular regulation Regulate production of proteins at any point during transcription/translation Differentiation Stem cells can turn into any type of cell Zygote = undifferentiated All genes are potentially active Once a cell differentiates genes are turned off permanently Regulation of genes can occur anywhere between chromosome and protein function Regulation of Chromosome Structure Heterochromatin- condensed, not expressed Euchromatin- uncondensed, expressed Histone modification Acetylation=prevents histones from binding to each other Creates looser structure DNA modification DNA Methylation Addition of methyl groups deactivates DNA Blocks RNA polymerase Epigenetic Inheritance Inheritance of DNA and chromosome modifications Bees (worker vs. queen) Potato famine diabetes Transgenerational epigenetic observations See main article Transgenerational epigeneticsTransgenerational epigenetics In the verkalix study, Marcus Pembrey and colleagues observed that the paternal (but not maternal) grandsons [56] of Swedish men who were exposed during preadolescence to famine in the 19th century were less likely to die of cardiovascular disease. If food was plentiful, then diabetes mortality in the grandchildren increased, suggesting that this was a transgenerational epigenetic inheritance. [57] The opposite effect was observed for femalesthe paternal (but not maternal) granddaughters of women who experienced famine while in the womb (and therefore while their eggs were being formed) lived shorter lives on average. [58]verkalix study [56]diabetes [57] [58] In a recent study investigating correlations among maternal stress in pregnancy and methylation in teenagers and their mothers, it has been found that children of women who were abused during pregnancy were significantly more likely than others to have methylated glucocorticoid-receptor genes, [38] which in turn change the response to stress, leading to a higher susceptibility to anxiety.stress [38] Regulation of Transcription Transcription factors bind to DNA, limit RNA polymerase Activators bind to enhancers, promote transcription Similar to operons RNA regulation RNA processing Alternative splicing mRNA degradation Micro RNA (miRNA) blocks or degrades RNA Small interferring RNA (siRNA) Regulatory proteins block attachment of ribosome at 5` end Protein Regulation Polypeptides must be processed before becoming active proteins Lifespan of protein Regulatory proteins are short lived Tagged with ubiquitin Proteosomes degrade tagged proteins Non-coding DNA 1.5% =exons 24%=introns 74.5% = repetitive DNA, non-coding regions, transposable elements Transposable elements Segments of DNA that move around Repeat many times Function unknown Alu repeats ~300 nucleotides long Unique to humans and primates Used for DNA fingerprinting Evolution of the genome Earliest life forms had very few genes Minimum necessary for survival Modern genomes are larger, more complex Non coding regions Regulatory genes Operons