MOD 6: Regulation of Expressions in Prokaryotes Flashcards
TRUE OR FALSE: Prokaryotic cells are generally larger than eukaryotic cells
FALSE; They are smaller
TRUE OR FALSE: Eukaryotic cells are round because they do not have cell walls
TRUE
What do you call the enzyme that deteriorates cell walls?
Cellulase
What factors affect the occurrence of transcription?
- Environment
- Cellular activities
- Replication
- Recombination
- Repair of DNA
- Cell division
This type of enzyme can be induced and it requires specific factors for it to do its job
Inducible enzyme
This type of enzyme is always functioning
Constitutive enzyme
This type of enzyme binds to the operator and tells it to stop working. It is produced by a repressor gene
Repressible enzyme
Genetic expression occurs unless it is shut off by a regulator molecule. What control is this?
Negative control
Transcription occurs only if a regulator molecule directly stimulates RNA production
Positive control
These refer to the genes coding for the primary structure of an enzyme
Structural genes
What are the three structural genes in the lac operon?
- lacZ (B-galactosidase)
- lacY (permease)
- lacA (transacetylase)
TRUE OR FALSE: Bacterial DNA have introns as well
FALSE; They do not
TRUE OR FALSE: Proteins are products of genes that will be operons
FALSE; Operons are products of genes that will be proteins
Lactose related genes are expressed when lactose is __________ and repressed when __________
Present; absent
These are genes that code for similar functions. They tend to be organized in clusters
Operons
This type of operon is affected by the presence of lactose
Lac operon
Which two scientists discovered the genetic regulatory mechanism, regulation of transcription, and obtain the 1965 Nobel Prize in Medicine?
Francois Jacob and Jacques Monod (Jacob Monod Lac Operon)
With lactose, the disaccharide is broken down into 2 monosaccharides. What are they?
Glucose and galactose
Lac operon produces an enzyme to break down lactose. What is this enzyme?
B-galactosidase
What are the two binding sites of the repressor protein?
Operator gene and lactose
What process does the repressor protein block?
Transcription
With the absence of lactose, it is repressed. Where does the repressor protein bind to?
It binds to the operator gene
With the presence of the repressor protein, its conformation is changed. Where does the repressor protein bind to?
It binds with the lactose
TRUE OR FALSE: The repressor protein can bind to the operator region with or without the presence of lactose.
FALSE; The repressor protein cannot bind to the operator region with the presence of lactose
Which does a cell prefer, lactose or glucose? What happens to the other?
The cell prefers glucose for glycolysis. Lactose then shuts down.
What type of control does the catabolite-activating protein (CAP) exert over the lac operon?
Positive control
What is the condition of glucose and lactose when:
- cAMP levels increase
- cAMP forms complex with cAP
- binds with cAP-binding site
- transcription and translation
- structural genes are expressed
Without glucose, with lactose
What is the condition of glucose and lactose when:
- cAMP levels decrease
- cAMP does not form complex with cAP
- no binding with cAP-binding site
- glucose cannot bind efficiently
- translation is diminished
With glucose, with lactose
TRUE OR FALSE: Lactose metabolism requires fewer steps and less energy compared to glucose metabolism.
FALSE; By using glucose first the cell maximizes energy efficiency
TRUE OR FALSE: The cell avoids unnecessary production of enzymes involved in lactose metabolism when glucose, a more readily metabolizable sugar, is available.
TRUE
TRUE OR FALSE: The CAP-cAMP system ensures that the lac operon is only fully activated when glucose levels are low and lactose is present.
TRUE
What happens to the repressor with the presence of tryptophan?
Tryptophan binds to the repressor, activating it
TRUE OR FALSE: Tryptophan is produced in the cell and cannot be obtained from the environment.
TRUE
TRUE OR FALSE: The DNA plays diverse roles in regulation gene expression in bacteria.
FALSE; RNA
What are the three types of regulation that fine-tune levels of gene expression in bacteria?
- Attenuation
- Riboswitches
- Small noncoding RNAs (sRNA)
TRUE OR FALSE:
DNA —> Transcribed to __________ —> decides if it will be converted to __________ or not
mRNA; protein
Which groups of scientist discovered attenuation?
Charles Yanofsky, Kevin Bertrand, and their colleagues
What is the condition of tRNA when:
- tRNA is uncharged
- transcription is slow
- 1-3 stem-loop is formed
tRNA is unavailable
What is the condition of tRNA when:
- tRNA is charged
- 1, 2, and 3 are separated
- 4 forms a loop
- termination hairpin is formed
tRNA is available
What is the condition of tryptophan levels when:
- ribosome translates slowly
- antiterminator is formed
Low tryptophan level
What is the condition of tryptophan levels when:
- ribosome translates quickly
- terminator hairpin and associated hairpin are formed
High tryptophan levels
This hairpin prevents the formation of the terminator and allows transcription to continue
Antiterminator (Non-terminating hairpin)
This begins at the ligand-binding site of the RNA
Riboswitches
Riboswitches involve short ribonucleotide sequences present in the __________ of __________
5’-untranslated regions; mRNAs
TRUE OR FALSE: The terminator conformation of riboswitches interfaces directly with the transcriptional machinery and shuts it down
TRUE
These play regulatory roles in bacteria
Small noncoding RNAs (sRNA)
These are involved in gene regulation and the modification of protein function
sRNAs
These are transcribed from the opposite strand of DNA and in the opposite direction, making them complementary to mRNAs transcribed from that locus
sRNA
Positive or negative regulation?
- sRNA binds to the ribosome binding site
- no translation
Negative regulation
Positive or negative regulation?
- ribosome binding site is now open for attachment of the ribosome
- translation proceeds, as RBS is unmasked
Positive regulation
CRISPR-Cas is an __________ in bacteria
Adaptive Immune System
CRISPR-Cas is an __________ in bacteria
Adaptive Immune System
Who first discovered nucleotide excision repair in 1964?
Paul Howard-Flandres
Who discovered attenuation?
Charles Yanofsky and Kevin Bertrand