Module 3 Regulation of Gene Expression at various levels Flashcards
(34 cards)
a unit of genetic function common in bacteria and phages;
consists of coordinately-regulated clusters of genes with related functions
OPERON:
a specific nucleotide sequence in DNA that binds RNA polymerase and indicates where to start transcribing RNA
PROMOTER
a segment of DNA to which a transcription
factor protein bind
OPERATOR:
a gene involved in controlling the expression of
one or more other genes; may encode a protein, or it may work at the level of RNA. In prokaryotes, regulator genes often code for repressor proteins.
REGULATORY GENES
protein that physically obstructs the RNA polymerase from
transcribing the genes.
REPRESSOR
a gene whose presence prevents the expression of some other gene at a different locus
INHIBITOR
a molecule that starts gene expression; can bind to repressors or activators; function by disabling repressors (gene is thus expressed)
INDUCER
Transcriptional Control Systems in Prokaryotes
Negative control
Positive control
regulatory protein shuts down transcription
negative control
regulatory proteins triggers trancription
positive control
negative control
a group of genes that are
used, or transcribed, together — that codes for the components for
production of tryptophan; present in many bacteria, but was first
characterized in Escherichia coli.
TRP OPERON (tryptophan operon)
an operon required for the
transport and metabolism of lactose in E. coli and some other enteric
bacteria; has three adjacent structural genes: lacZ, lacY, and lacA.
LAC OPERON (lactose operon)
T or F
Positive control is also demonstrated by the lac operon.
T
CLASSES OF SEQUENCES:
Each producer may have several receptor sites, each responding to one activator so that a single activity
though can recognize several genes. However, different activators
may activate the same gene at different times
. Producer genes or structural genes
CLASSES OF SEQUENCES:
one such receptor site is assumed to
be present adjacent to each producer gene or a set of such producer
genes
Receptor site or operator gene
CLASSES OF SEQUENCES:
responsible for synthesis of an activator RNA that may or may not give rise to proteins before it activates the receptor site; may also fall in cluster with same sensor
sites.
Integrator gene or regulator gene -
CLASSES OF SEQUENCES
regulates activity of integrator gene which can be
transcribed only when the sensor is activated; sensor sites are
recognized by agents which, like hormones and proteins, change the
pattern of gene expression. (ex: hormone-protein complex or a
transcription factor may bind to a sensor site and cause the
transcription of integrator)
Sensor site
are DNA sequences that bind to the RNA
polymerase II enzyme. They are binding sites of transcription factors.
PROMOTERS
are DNA sequences that, when bound by
transcription factors, enhance the transcription of an associated
gene.
ENHANCERS
Addition of 7-methyguanylate to the 5’ end occurs
shortly after the beginning of transcription.
5’ capping
After transcription termination, cleavage
and polyadenylation specificity factors (CPSF) bind to a poly(A) signal
sequence, typically AAUAAA, and another protein complex, cleavage
stimulation factor (CStF), interacts with a downstream G/U signal.
3’ polyadenylation
he eukaryotic RNA transcript has INTERRUPTED GENES which means that there are alternating introns (non-coding sequences) and exons (coding sequences).
Splicing
The cell can select different splice sites by
producing splicing repressor proteins or splicing activator proteins that
bind to alternate splicing sites and therefore, direct the spliceosomes to
different splicing sites or block a site altogether
Alternative Splicing
separation of mature rRNA from the primary
transcript (generated by RNA pol I)
Nucleolytic cleavage
