2.22.07 - 2.22.2007 Suppression mutation a separate...

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2.22.2007 Suppression mutation – a separate mutation that happens at a separate gene sequence that restores the phenotype that was lost in an earlier forward mutation (it’s the second mutation) o If a mutation stops a certain protein from being able to bind to its DNA binding domain and another nucleotide changed at the DNA binding domain then after the protein does bind to the sequence and it is functional again, this second mutation is the suppression mutation o If you work in research long enough, particularly with organisms that you’d see reproduce in large numbers you have a real chance of seeing a suppression mutation (flies) o In bacteria, just because of the sheer number of organisms your working with, rare things happen all the time o Some procedures that are done with bacteria, the suppression can happen so often its something you have to take into account o It’s a real event not a theoretical possibility CUT OFF FOR EXAM I Bacteria: easier to work with because they are smaller, fewer components, easier to study, processes of the cells are simpler like transcription but similar to that in eukaryotes o Easy to manipulate bacteria to produce things for us like DNA sequences (many copies of a certain gene to study it – called molecular cloning) Makes proteins for industry, pharmaceuticals, they are very useful producers Simplest broth: water, a carbon source (glucose if its not specified but it is usually glucose), salts o Why a carbon source? For cellular respiration which provides energy Called a carbon source because its used to build just about everything A cell has a high need for carbon, so if it needs it it comes from the broth o Salts All the molecules that cells need to build don’t just contain C, H, O and what comes from the air, there are a lot of other elements needed, and these are grouped together and called salts o You can take a small amount of bacteria and broth put it someplace warm and shake it which provides lots of oxygen, and then the next day you have tons of bacteria, broth is used for rapid growth of bacteria o What makes broth work so well for rapid growth is that each cell is free floating individually but this makes it so you cannot identify characteristics of an individual bacteria but it does allow for easily getting rid of wastes and getting in food Agar is another kind of medium, agar type media of the simplest variety contains (water, carbon source (glucose probably), salts, and agar (comes from seaweed, think of it as gelatin – powder added to hot broth and while its still hot it is liquid so you can pour it into Petri dishes and as it cools it sets up as a semi sold – like jello) o What is the benefit of growing bacteria on a semisolid, its semi-solid so wastes can still diffuse away and nutrients can diffuse in o But it’s a solid so as you streak bacteria over the surface individual bacteria land separately so you have individual bacteria on the plate, they are able to grow and divide and reproduce individually so that
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2.22.07 - 2.22.2007 Suppression mutation a separate...

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