Term
| 3'-untranslated region (3'-UTR) |
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Definition
| is a particular section of mRNA that follows the coding region that is not translated. These are found in both prokaryotes and eukaryotes |
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Term
| 5'-untranslated region (5'-UTR) |
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Definition
| also known as the leader sequence, is a particular section of mRNA and the DNA that codes for it. Stats at the +1 position (where transcription begins) and ends one nucleotide before the start codon. Usually contains ribosome binding site-maybe a hundred or more nucleotides long |
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Term
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Definition
| this is a second mechanism of negative feedback in the trp operon. This is made possible by the fact that in prokaryotes, (which have no nucleus) the ribosomes begin translating the mRNA while RNA polymerase is still transcribing the DNA sequence. This allows the process of translation to directly affect transcription of the operon |
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Term
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Definition
| plays an important regulatory role in prokaryotic cells because of the absence of the nucleus in prokaryotic organisms. It refers to a specific regulatory sequence that, when transcribed into RNA forms hairpin structures to stop transcription when certain conditions are not met. |
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Term
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Definition
| is a hydrolase enzyme that catalyzes the hydrolysis of ß-galactosides into monosaccharides. |
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Term
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Definition
| is a second messenger important in many biological processes. It is used for intracellular signal transduction such as transferring the effects of hormones like glucagon and adrenaline which cannot pass through the cel membrane. It is involved in the activation of protein kinases |
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Term
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Definition
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Term
| CAP (catabolite activator protein) |
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Definition
| is a regulatory protein in bacteria. It binds cAMP, which causes a conformational change that allows the protein to bind tightly to a specific DNA sequence in the promoters of the genes it controls. |
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Term
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Definition
| is an important part of global control system of various bacteria and other micro-organisms. Catabolite repression allows bacteria to adapt quickly to a preferred (fast matabolisable) carbon and energy source first. Can be initiated by glucose. |
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Term
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Definition
| tri nucleotide sequences which determine amino acid sequencing (proteins) |
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Term
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Definition
| are enzymes that are not controlled by induction or repression (they just keep doing their thing regardless of circumstances) |
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Term
| CRP (cAMP receptor protein) |
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Definition
| s a regulatory protein in bacteria. It binds cAMP, which causes a conformational change that allows the protein to bind tightly to a specific DNA sequence in the promoters of the genes it controls. |
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Term
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Definition
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Term
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Definition
| is a molecule that starts gene expression. For a gene to be expressed, its DNA sequence must be copied, to make mRNA. Inducers function by disabling repressor proteins |
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Term
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Definition
| is an enzyme that is expressed only under conditions in which it is clear of adaptive value, as opposed to constitutive enzyme which is produced all the time. Typically used for the breaking down of things in the cell. Inducers cause the gene to turn on (controlled by the amount of reactant which turns the gene on)- can also remove the repressor |
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Term
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Definition
| this involves the binding of a repressor to the operator to prevent transcription. |
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Term
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Definition
| is a DNA sequence that does not contain a stop codon in a given reading frame. These are often used along with other evidence to initially identify candidate protein coding regions in a DNA sequence |
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Term
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Definition
| a segment of DNA that a regulator binds to. It is classically defined as a segment between the promoter and the genes of the operon. In the case of a repressor, the repressor protein physically obstructs the RNA polymerase from transcribing the genes. |
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Term
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Definition
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Term
| polynucleotide phosphorylase |
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Definition
| is a bifunctional enzyme with a phosphorolytic 3' to 5' exoribonuclease activity and a 3' terminal oligonucleotide polymerase activity. It is involved with mRNA processing and degradation in bacteria, plants and humans. |
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Term
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Definition
Can also regulate positively by an activator protein, which stimulates transcription by binding to DNA
-inducer binds to activator protein and causes a conformation change allowing it to bind to the DNA and begin transcription
-or the activator proteins are normally bound to the DNA, however when a corepressor is bound by the activator it is prevented from binding to the DNA. This stops activation and transcription. |
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Term
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Definition
| is a RNA molecule that has not yet undergone any modification after its synthesis. For example a precursor messenger RNA (pre-mRNA) is a primary transcript that becomes a messenger RNA after processing |
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Term
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Definition
| a nucleotide sequence that enables a gene to be transcribed. The promoter is recognized by RNA polymerase, which then initiates transcription. |
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Term
| promoter upstream element (UP element) |
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Definition
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Term
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Definition
| is a method for examining a cellular process occurring over time by successively exposing the cells to a labeled compound (pulse) and then to the same compound in an unlabeled form (chase). Radioactivity is a commonly used label. |
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Term
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Definition
| is a DNA binding protein that regulates the expression of one or more genes by binding to the operator and blocking the attachment of RNA polymerase to the promoter, thus preventing transcription of the genes. They are coded for by regulator genes. Inducers can interact with repressors and cause them to detach from the operator. |
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Term
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Definition
| is a type of nuclease that catalyzes the degradation of RNA into smaller components. Can be either endoribonucleases or exoribonucleases. |
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Term
| What are the methods of regulation |
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Definition
| Bacterial transcription can be either constitutive or regulated. Transcription of some operons is subject to repression , or is positively regulated by activation. Attenuation is another mechanism of regulation used for regulation of some operons encoding enzymes for amino acid biosynthesis. |
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Term
| What ways can operons be regulated |
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Definition
-repression
-attenuation
-can be positively regulated by activation |
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Term
| What is catabolite repression? |
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Definition
| Glucose is the preferred carbon source, so in the presence of glucose, many operons are turned off. These operons are activated by the CRP-cAMP complex which forms in the absence of Glucose. |
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Term
| A transcriptive cascade controls regulation of what |
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Definition
| Both the lytic and lysogenic pathways in lambda. |
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Term
| What is the key determinant in the switch between lysis and lysogeny |
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Definition
| The binding of repressors at OR |
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Term
| Bacterial mRNAs may be _____ or ______ meaning they have one or more ORFs. |
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Definition
| monocistronic, polycistronic |
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Term
| T or F Bacterial mRNA have long half lives and tRNA and rRNAs are much less long lived |
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Definition
| False its the reverse case |
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Term
| Where does the most regulation in bacteria occur |
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Definition
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Term
| What does the lac operon (lacZYA) encode for? |
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Definition
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Term
| How is transcription of the lac operon induced? |
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Definition
| By the presence of lactose or IPTG in the medium |
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Term
| How does the lac repressor repress transcription? |
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Definition
| The lac repressor binds to the lac operon. Binding of the inducer to the Lac repressor prevents the repressor from binding to the operator, and transcription can proceed. |
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Term
| T or F E.coli uses galactose in preference to lactose or other sugars, and the presences of this inhibits expression of the lac operon |
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Definition
| False. Glucose is the preferred sugar, and its presence inhibits the expression of the lac operon |
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Term
| What is low in the presence of glucose |
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Definition
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Term
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Definition
| It is a transcriptional activator that forms in the absence of glucose. |
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Term
| What causes negative regulation and positive regulation in the lac operon? |
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Definition
| The lac repressor causes negative regulation, and CRP-cAMP causes positive regulation |
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Term
| What binds to an activator site in the lac operon |
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Definition
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Term
| E.coli rRNA primary transcripts contain ____ rRNAs and ____ tRNAs. These must be processed to produce mature ___, _____, and _____ rRNAs |
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Definition
| 3, several, 16S, 23S, 5S, |
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Term
| tRNAs are also processed. Where does processing occur and how? |
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Definition
| They occur at both the 5' and 3' end, and they are produced by modification of bases. |
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Term
| The trp repressor does what |
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Definition
| Acts to repress the transcription of the trp operon. |
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Term
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Definition
| It acts as a corepressor to allow the Trp repressor to bind to the operator to repress transcription. |
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Term
| In attenuation the trp leader region can form what? This region does what? |
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Definition
| It can form two mutually exclusive hairpin structures. It encodes a short peptide and has two trp codons. |
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Term
| What happens under low tryptophan conditions? |
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Definition
| Ribosomes will pause at the Trp codons and allow formation of the antiterminator hairpin structure and transcription proceeds. (2-3 Bind) |
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Term
| What happens under high tryptophan levels? |
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Definition
| Ribosomes read through the trp codons and the transcription terminator hairpin structure will form. Transcription terminates before RNA polymerase reaches the tryptophan biosynthetic genes |
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Term
| What promoters help determine whether lambda undergoes lysis or lysogeny? |
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Definition
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Term
| PR and PL are regulated by what |
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Definition
| OR and OL operator regions, each which have three operator sites. |
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Term
| The in which ____ binds to ___ and ___ determines whtere lambda enters the lytic or lysogenic state. |
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Definition
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Term
| The lac repressor binds to what site within the lac operon? |
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Definition
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Term
| Name all the parts of the lac operon |
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Definition
| The lacO, LacZ, LacA,LacP |
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Term
| The lac repressor is inactivated by binding to which of the following? |
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Definition
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Term
| T or F- A polycistronic mRNA is transcribed from the lac operon when lactose is present and glucose is absent in the E. coli cell. |
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Definition
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Term
| The lac repressor protein is active in the absence of lactose within the cell |
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Definition
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Term
| In the trpL mRNA, the attenuator sequence is located closest to what stem loop region? |
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Definition
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Term
| If transcription is proceeding without pausing, what stem loop structures are formed in the trpL mRNA? |
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Definition
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Term
| T or F-The process of attenuation is the trp operon turns off the operon when it is not needed by the cell? |
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Definition
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Term
| If regions 1 and 2, and 3 and 4 of the trpL mRNA form stem loops, the trpE gene will be transcribed. |
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Definition
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Term
| The inducer for the lac operon is |
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Definition
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Term
| What is the most convincing evidence that lacI is a diffusible protein? |
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Definition
| A partial diploid with only one functional lacI gene is able to regulate both copies of the lac operon |
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Term
| T or F-Genes within an operon are generally involved in the same biochemical pathway? |
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Definition
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Term
| T or F- Catabolite repression requires an inducer and an activator protein. |
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Definition
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Term
| What is not a structural gene of the lac operon |
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Definition
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Term
| What lac operon element, when nonfunctional would lead to a reduction in the total amount of functional lacZ produced by a bacterial cell? |
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Definition
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Term
| Attenuation of the trp operon occurs when |
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Definition
| in presence of high levels of tryptophan |
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Term
| Why does the ribosome stall on region 1 during attenuation |
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Definition
| Translation of this region requires trp-tRNA (trp) |
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Term
| Why can it be beneficial for bacterial cells to have multiple cistrons on one mRNA? |
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Definition
| Often polycistronic mRNAs encode proteins in a specific metablic pathway. When they are all together, their synthesis is regulated coordinately, and a single signal will cause similar quantities of related proteins to be produced at the same time |
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Term
| How can the lac operon ever be induced if the lactose operon inducer ( the protein that binds to the repressor) is allolactose in the cell, a product of the lac operon enzymes |
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Definition
| The binding of a repressor is never infinitely strong. Sometimes (meaning approximately once a generation) the protein will come loose and RNA polymerase will be able to transcribe the gene. This is basal level of transcription. This allows permease to bring into the cell and ß galactosidase is available to convert a small amount of lactose into allolactose. The allolactose binds to the repressor, causes it to change conformation so that it falls off the operator. RNA poly, can then freely transcribe the lac genes making the lac enzymes much more readily |
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Term
| What does the lac operon encode |
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Definition
| The lac operon codes for ß galactosidase, which metabolizes lactose into glucose and galactose, permease, which helps lactose to enter the cell, and ß galactoside transacetylase, which has an unknown function |
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Term
| What does the trp operon encode? |
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Definition
| The trp operon codes for three enzymes that are essential for tryptophan (an amino acid) synthesis. |
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Term
| The attenuation of tryptophan depends on what |
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Definition
| the secondary structure of the mRNA (formation of the 3-4 hairpin) |
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Term
| What are the DNA sequence components of the trp operon? |
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Definition
| Promoter, operator, leader (with attenuator), trpE, trpD, trpC, trpB, trpA |
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Term
| Why is it strange to have two adjacent tryptophan codons? |
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Definition
| It is rare because normally tryptophan accounts for only 1% of amino acid residues in a protein |
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Term
| How does a cell know to metabolize glucose rather than lactose? |
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Definition
| Glucose is involved in the inhibition of phosphorylation of adenylate cyclase which prevents cAMP formation. With no cAMP, the cAMP-CRP complex cannot form and therefore cannot bind to its activator site upstream from the promoter to activate synthesis. |
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Term
| What is another way that glucose can slow lac operon expression? |
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Definition
| It can act through an inducer exclusion mechanism. In this mechanism, a product of glucose (EIIA) binds to lactose permease (the product of the lacY gene) which inactivates it. This prevents lactose from entering the cell and being converted into allolactose. With no allolactose, the repressor protein will remain bound to the operator. |
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Term
| The E. coli ____ gene codes for ß-galactosidease |
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Definition
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Term
| ___ is the a true inducer of the lactose operon. |
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Definition
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Term
| The segment that codes for a polypeptide chain is called |
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Definition
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Term
| The ___ complex binds to an activator site upstream from the lac promoter and activates lac operon transcription |
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Definition
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Term
| Catabolite sensitive operons cannot be induced if what is present |
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Definition
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Term
| Negative ____ occurs because the gene product regulates tis own synthesis. |
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Definition
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Term
| What does bacteria use to degrade mRNA |
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Definition
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Term
| What does the lac y gene code for |
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Definition
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Term
| What does the lac a gene code for |
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Definition
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Term
| What does the lac I code for |
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Definition
| the repressor (which binds to lac O or the operator when the inducer is absent- Allolactose is the inducer) |
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Term
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Definition
| CAP-cAMP, and RNA polymerase |
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Term
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Definition
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