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.

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 lac operon in e.coli (what’s e. coli?)

• The lac operon is ________ __________________________________… 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 trp operon also only turns on when it is necessary• Trp operon 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