Bacterial Gene Structure and Regulation - Howe Flashcards
What is the most common structure of bacterial chromosome?
double-stranded, single circular molecules.
There are often multiple circular molecules.
What distinguishes extrachromosomal elements from chromosomal?
if they are essential for bacterial growth under normal circumstances.
What are variable chromosomal elements?
DNA strands present only in some strains.
What is a stimulon?
mutliple genes and operons whose expression is controlled by a single stimulus
(ex: heat-shock)
Do prokaryotic genes have introns?
no. The gene and polypeptides are colinear. As soon as it is translated to mRNA, it can be transcripted to a polypeptide. This often occurs while translation is still happening.
A seqeunce of mRNA has a 5’ 7-methly GTP cap and a 3’ poly-A tail. What type of cell produced it: prokaryotic or eukaryotic?
Eukaryotic.
Prokaryotic mRNA does not have 5’ 7-methyl GTP caps or 3’ poly-A tails. They also lack introns.
A set of proteins are identified as all having a N-formyl methionine at their start. What type of cell produced them: prokaryotic or eukaryotic?
prokaryotic proteins initiate with N-formyl methionine.
Neutrophils and monocytes in humans use N-forymlated peptides as chemoattractants.
What is a transition mutation?
Transversion?
change of a purine to another purine, or a pyrimidine to another pyrimidine.
Transversion is the mutation of a purine to a pyrimidine or a pyrimidine to a purine.
What are the purines? Pyramidines?
Purines: AG (agriculture is pure)
Pyrimidines: CT (egyptians are obsessed with cats)
What small molecule effector is used in catabolite repression for glucose levels? How is its concentration related to that of gluclose?
cyclic-AMP.
It is inversely related to glucose levels. The more glucose available, the less cAMP to repress glucose catabolism
What the regulatory protein involved in catabolite repression?
CAP (catabolite actovator protein). Binds to promoter region of lac operaon, turning on transcription. It requires cAMP to form a complex to bind to DNA promoter region.
If glucose and lactose levels are both low, what will the lac operon do? What mediates this?
Low glucose will promote high cAMP. Low lactose will leave repressor unbound and active, suspending any lac operon translation. Uses repression and attenuation as controls.
What is the Trp operon?
contains five enzymes needed for biosynthesis of AA tryptophan.
When there is excess Trp, what will happen to the Trp operon?
repressor will be bound and activated, preventing transcription?
If Trp levels are high, what will happen with the leader region of the Trp operon?
It will be transcripted rapidly, but the high Trp levels will bind 3-4 in a hairpin and terminate it, preventing downstream transcription
