Eukaryotic Gene Regulation
Have you ever wondered? • Every cell in our bodies has exactly the same DNA… and DNA makes everything in our bodies… • How does it know when to be a skin cell and when to be a stomach cell or a neuron? • THE ANSWER IS… _________________
When are genes controlled? • In Eukaryotes genes can be controlled at any of the steps of protein synthesis… • During ______________ • During ______________ • ________________ • Even _______________ proteins can be stored before activating them because they are waiting for some modification (ex. phosphorylation) to get active
During Transcription • During transcription enzymes called ___________ __________ are used to regulate gene expression • Transcription factors can be • ____________: proteins that bind to enhancer sequences on the DNA speeding up transcription • ____________:proteins that bind to silencer sequences on the DNA slowing down transcription
Transcription continued • To begin transcription, general transcription factors need to help ____________ bind to the ______________ • This gets the gene ready to be transcribed but __________________must be added to completely start or turn off transcription
Special gene packaging and transcription • To turn UP transcription __________ bind to _______________________ _________________strand • To turn DOWN OR OFF transcription _______________________ bind to ___________________ on the DNA. • Eukaryotes bend so the same enhancers are around ALL of the genes that need for a specific function • This is accomplished by winding the DNA around proteins, called ______________ • This also keeps them organized and the appropriate enhancer or repressor around the gene(s) they control
During Processing • Different splicing or processing affects where, within the cell, the protein is made and in what order.
Translation • Some RNAs last longer and get copied multiple times before they are broken down by the cell’s enzymes (_____________). • RNA interference is when __________ ________________________________________with their sequence.
Cancer… when gene regulation goes wrong • In healthy cells there is an inhibitor for cell reproduction • When that inhibitor gets broken the cell starts to divide uncontrollably • Oncogene • Genes we know have the potential to mutate but are currently normal are proto-oncogenes • Also there are cells that are supposed to stop excess growth (tumor suppressor genes) but they also become mutated to no longer suppress it.
Cancer Causes • Because of the combo of things that cause cancer it is not usually a single event that gives you cancer • The more you can avoid potential carcinogens (things that cause the mutations that cause cancer) the lower your risk.
Outcomes of gene controls: x-inactivation • Clearly, we learn from males, ______________ • What do we do with the other ones? • Mammals undergo ________ ___________ • The inactivated X in balled up in a barr body where it is not used at all except during interphase. _____________ __________________ • This is rarely visible… one notable exception is the tortoise shell cat where fur color is controlled by the X
Master Genes • The expression of some “Master Genes” starts a cascade of activity in other genes. • The protein produced by a master gene generally acts as _________________ ___________________________________________________
Homeotic Genes (Eukaryotes) • In Eukaryotes all of the Master genes are collectively called ___________________ _______________ • These genes ______________ ______________________________such as eye formation, limb production, segmentation etc. • They have been extensively studied in many species.
Knockout Fruit Flies • Homeotic genes were primarily discovered in ___________________________. • When a gene is suspected of being a ‘master gene’ scientist perform a Knockout Experiment on them • A knockout experiment is when _________________________________________________________ ______________________________ • The role of the gene is then found by observing what ‘problem’ it caused in the organism • They are named accordingly– wingless, minibrain etc.
Prokaryotic Gene Regulation
Basics of PROKARYOTIC gene regulation • Before any specific region of DNA that is transcribed there is a ___________ • Then there is an _________… this is an on off switch for the gene • ____________________________________ ________________________________________________________________________
Repressors (positive control… presence activates) • Repressors ____________ ____________________ ____________________ • Take the lacoperon in e.coli(what’s e. coli?) • The lacoperonis ________ __________________________________… then it turns on to make the enzyme that breaks down lactose. • The thing that keeps it turned off is called a repressor (made by the regulatory gene upstream of the promoter)
Another repressor (negative control… presence inhibits) • The trpoperon also only turns on when it is necessary • Trpoperon makes tryptophan (an amino acid) • If the organism is ingesting trp, it won’t use the energy to make it from scratch… so _____________________________ __________________________________________________________________ activated repressed