Chapter 15, 17, 18, 19 Flashcards
A model proposed by Jacob and Monod whereby a group of genes is regulated and expressed together as a unit.
Operon model
How does lacI gene regulate the transcription of the structural genes?
By producing a repressor molecule, and that the repressor is allosteric, meaning that it reversibly interacts with another molecule, causing both a conformational change in the repressor’s three-dimensional shape and a change in its chemical activity.
Because transcription occurs only when the
repressor fails to bind to the operator region, regulation is said to be under?
negative control
If a regulator gene needs to be located adjacent to the gene it regulates, it is said to be?
cis-acting factor (example: O region in lac operon)
If a regulator gene does not need to be located adjacent to the gene it regulates, it is said to be?
trans-acting factor (example: I gene in lac operon)
A molecule called the catabolite-activating protein (CAP) helps activate expression of the lac operon but is able to inhibit expression when glucose is present. This inhibition is called?
catabolite repression
True or False. For maximal transcription of the structural genes, the repressor must be bound by lactose (so as not to repress lac operon transcription), and CAP must be bound to the CAP-binding site.
True
This enzyme catalyzes the conversion of ATP to cyclic adenosine monophosphate.
adenyl cyclase
What is the role of glucose in catabolite expression?
inhibits the activity of adenyl cyclase
When both RNA polymerase and cAMP-CAP complex are together in the presence of the lac promoter DNA, a tightly bound complex is formed. This is an example of a phenomenon called?
cooperative binding
Tryptophan is referred to as ____ because is participates in the repression of genes coding tryptophan synthesizing enzymes.
corepressor
When tryptophan is present and the trp operon is repressed, initiation of transcription still occurs at a low level but is subsequently terminated at a point
about 140 nucleotides along the transcript. This process is called?
Attenuation
The site involved in attenuation is located 115 to 140 nucleotides into the leader sequence and is referred to as?
Attenuator region
The initial DNA sequence that is transcribed gives rise to an mRNA sequence that has the potential to fold into two mutually exclusive stem-loop structures referred to as?
hairpins
In the presence of excess tryptophan, the mRNA hairpin that is formed behave as a ____ structure, and transcription is almost always terminated prematurely, just beyond the attenuator.
terminator hairpin
If tryptophan is scarce, an alternative mRNA
hairpin referred to as the ______ is formed.
antiterminator hairpin
Biosynthesis of which amino acids uses attenuation as regulatory mechanism?
- tryptophan
- threonine
- histidine
- leucine
- phenylalanine
Are mRNA sequences (or elements) present in the
5’-untranslated region (5’-UTR) upstream from the coding sequences. These elements are capable of binding with small molecule ligands, such as metabolites, whose synthesis or activity is controlled by the genes encoded by the mRNA.
riboswitches
It is the ligand binding site within a riboswitch.
aptamer
It one of the domains of a riboswitch capable of forming the terminator structure.
expression platform
True of False. Eukaryotic gene expression is influenced by chromatin modification.
True
In the interphase nucleus, each chromosome occupies a discrete domain called a _______ and stays separate from other chromosomes.
chromosome territory
Channels between chromosomes contain little or no DNA and are called ____?
interchromosomal domains.
Are nuclear sites at which most RNA polymerase II transcription occurs. These sites also contain the majority of active RNA polymerase and other transcription factors.
transcription factory