Microbiology Unit 2 Pt. 3

Front 1

What is an operon, and what's "upstream/downstream?"

Back 1

operon is a segment of dna that contains a group of genes that code for proteins that together CATALYZE a particular process (they don't do it themselves)

upstream/downstream: the stream is the direction the operon is read.

Front 2

what are the parts of a typical operon? In order.

Back 2

from upstream to downstream: regulatory gene, promoter region, operator region, structural genes

Front 3

what is the promoter region

Back 3

the site of initiation of gene transcription

Front 4

what is the operator region?

Back 4

the regulatory site of the operon - where a repressor can bind to stop rna polymerase from connecting to the operator (thereby blocking the initiation of of transcription)

Front 5

what are the two main mechanisms for regulation of gene expression? What cases, in general, are the two used for?

Back 5

Repression is mainly for things that are on by default - stuff you always need and are almost always being made (for example, TRYPTOPHAN). In this case, an inactive repressor (just a protein floating around that can't do much) meets the product (tryptophan, for example, a CO-REPRESSOR) and suddenly becomes capable of bonding to the operator and blocking rna polymerase. More product = more blocking.

Induction is the opposite, for things that are needed at certain times. There's an active repressor always sitting on the operator and blocking the structural genes, but a particular CO-REPRESSOR (like lactose, that needs enzymes to digest it) bonds to that repressor it falls off the operon and enzymes can be made.

Front 6

how do anabolic and catabolic systems fit in with regulation mechanisms?

Back 6

in anabolic systems, structural genes are transcribed until they are repressed

Front 7

what are inducible genes?

Back 7

genes that can be turned on by the presence of inducers.