Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
30 Cards in this Set
- Front
- Back
|
Gene Expression in Eukaryotes
|
* Genes are split into introns and exons
* mRNA splicing and transcription occur in the nucleus * translation occurs in the cytoplasm |
|
|
Gene Expression in Prokaryotes
|
* transcription and translation are coupled
* mRNA is translated immediately after transcription |
|
|
RNA polymerase in Bacteria
|
* consists of a core enzyme with four subunits (α, α, β, β')
* promotes or catalyzes polymerization * utilizes accessory proteins, sigma (σ) factors |
|
|
Sigma (σ) Factors
|
* participate in the initiation of polymerization
* may have a major σ factor that regulates gene expression under normal conditions and a σ factor that regulates gene expression under alternative conditions |
|
|
Promoter
|
* where the σ factor and RNA polymerase bind to start txn
* consist of consesus sequences: - 35 box - 10 box (TATA or Pribnow box) |
|
|
Terminator Sequences:
- Intrinsic Terminator - Rho-dependent Terminator |
* sequence where txn is terminated
* Intrinsic: forms a stem-loop structure in the RNA transcript that signals the RNA polymerase to stop txn * Rho-dependent: takes advantage of a protein that scans along the DNA |
|
|
Unit of Transcription
|
* region between the promoter sequence and terminator sequence
* mammals: one gene = one unit of txn * bacteria: one unit of txn = several genes costranscribed together in a polycistronic mRNA (operon) |
|
|
Polycistronic
|
* multiple genes are encoded in the same mRNA
|
|
|
Operon
|
* one unit of transcription in bacteria
* goes through the promoter, genes of interest, until the terminator sequence |
|
|
Polar Effect
|
* a mutation in an upstream gene can stop txn, gene expression, and possibly tln of a downstream gene
|
|
|
Complement Test
|
* allows you to figure out if you have a mutation in gene one or a mutation in gene one that has a polar effect on genes two and three
* introduce normal copies of gene one, two, or three and see which one restores your phenotype |
|
|
Regulon
|
* refers to a set of operons that are coregulated
* when a cell is responding to a change in conditions, you need to regulate multiple operons simultaneously |
|
|
Lac Operon
|
* regulated in response to nutrient conditions
* if no glucose, but lactose is present, genes for metabolizing lactose are upregulated * lactose absent: repressor binds to the operator * lactose present: inducer binds to the repressor, which falls off the operator = txn of lac genes |
|
|
Mal Operon
|
* bacteria want to upregulate the genes for maltose when present
* no maltose (the inducer): without binding of the inducer to the activator, the activator cannot bind to RNA polymerase; the RNA pol doesn't bind efficiently * maltose present: maltose (the inducer) binds to the activator, which then binds to the RNA polymerase = txn |
|
|
Global Control Systems
|
* systems that regulate the expression of many different genes at the same time
* Ex: Catabolite Repression System |
|
|
Catabolite Repression System
|
* allows cells to regulate the expression of genes in response to glucose levels
* low levels of glucose: high levels of cAMP, which bind to CAP, which binds to the activator near the promoter region = txn of lac operon * high levels of glucose: low cAMP levels = no txn of lac operon |
|
|
cAMP
|
* cyclic AMP
* regulates the Catabolite Repression System * starvation signal * can bind to catabolite activator protein (CAP) |
|
|
Quorum Sensing
|
* regulated in response to bacterial number
* uses a small signal molecule called acyl homoserine |
|
|
Stringent Response
|
* like catabolite repression, senses nutrient levels
* regulated in response to AA levels and mediated by ppGpp * ppGpp signals bacteria to halt process of protein synthesis and synthesize AA instead |
|
|
ppGpp
|
* an alarmone involved in stringent response that signals the environment is AA poor
* signals bacteria to halt protein synthesize and initiate amino acid synthesis instead |
|
|
Two Component Systems
|
1) signal produced by binding of signalling molecule to histidine kinase
2) binding causes dimerization of HK 3) dimerization causes autophosphorylation of histidine residue 4) phosphotransfer rxn: the phosphate group is transferred to an aspartic acid on the response regulator 5) activated response regulator activates or represses txn |
|
|
Histidine Kinase
|
transmembrane protein that can sense extracellular conditions
Ex. pH, divalent cations [ ] |
|
|
Response Regulator
|
* DNA binding protein
* could be a positive or negative regulator: - activate txn - repress txn |
|
|
Bacterial Ribosome
|
* smaller number of protein components and RNA
* targeted by gentamicin and erythromycin * 80% remain in the cytoplasm * 20% in membrane, periplasm, secreted |
|
|
Sec Pathway Summary
|
* all proteins have a signal sequence (30 AA tag at N terminus)
* signal recognition protein (SRP) Sec B helps to recognize the signal sequence of the unfolded protein and target it to the secretory machinery * Sec A is an ATPase - ATP hydrolysis helps thread the protein through a pore in the membrane * Sec Y, E, and G make up the transmembrane pore * as the protein is targeted to the pore and threaded through, sometimes the SS is cleaved |
|
|
Sec Pathway - Gram Positive
|
* the pathway delivers proteins to the outside of the cell
|
|
|
Sec Pathway - Gram Negative
|
* they have an additional membrane, so the general secretory pathway only delivers proteins as far as the periplasm
|
|
|
Type III Apparatus
|
* consists of 20 proteins that form a needle that spans both membranes and punctures the eukaryote membrane
|
|
|
Type III Secretory Pathway
|
* contact with host cell mediated by a host receptor and bacterial adhesin
* needle is inserted with a special tip complex that mediates insertion into host cell membrane * a pore is created, allowing bacterial proteins (effector molecules) to enter the eukaryotic cell |
|
|
Effector Molecules
|
* bacterial proteins that enter the host cell
* can prevent the membrane from undergoing changes in shape (prevents phagocytosis) * can cause changes in host cell that allows the bacteria to be engulfed |
