Which is incorrect about inducible operons

What is the term that describes this process? Hydrogen Sulfhydryl Non polar covalent Peptide Polar covalent. A mutation that changes a normal codon to a stop codon is called a Point mutation Nonsense mutation Silent mutation Missense mutation Back mutation. DNA polymerase. Iowa Mutation Koch Cancer Ames. All of the following pertain to nitrogenous bases except Cytosine and thymine are pyrimidines Form pairs by hydrogen bonding Adenine pairs with thymine Guanine pairs with uracil Allows variation from one nucleotide to another which creates the encoded information.

A coenzyme The reactant A cofactor The substrate The product. All mutations are not beneficial to the cell. The process in which mutations are removed and the correct bases added is called Back-mutation Frameshift Transformation Transduction Excision repair. Which of the following is not a type of microRNA?

Which of the following is not a type of bacterial DNA recombination? Conjugation Mitosis Transduction None of the above Transformation. Which is incorrect about inducible operons? Have genes turned off by a buildup of end product Are often for catabolic pathways Are normally turned off Include the lac operon Are turned on by the substrate of the enzyme.

DNA helicase. Copy point Template Scaffold Reservoir Comparison molecule. Transcription occurs in the nucleus or at the nucleoid. Which of the following is not associated with a prokaryotic ribosome? Has a peptide P site Has an amino acid A site Has an exit site Is a 70s Small unit provides the enzymes for making peptide bonds. Missense and insertion Insertion and nonsense Deletion and insertion Nonsense and deletion Missense and nonsense.

Which of the following is not true of transposons? Excised introns form structures called lariats. Nonsense Deletion Missense Insertion Silent. DNA photolyase, in the presence of visible light, can repair DNA damage due to ultraviolet radiation. The development of virulent, toxin-producing bacterial strains due to the presence of a temperate phage can occur in Specialized transduction All of the choices are correct Transformation Generalized transduction Bacterial conjugation. DNA replication proceeds in one direction around the bacterial chromosome.

Are structural genes coding for proteins Is inherited Are the expressed traits governed by the genes Are regulatory genes controlling gene expression Are genes coding for RNA. Triplet Exon Operator Gene Intron. Full induction of the lactose operon requires Lactose and glucose present Lactose present without glucose Lactose present All of the choices induce the lactose operon Lactose and arabinose present.

Lactose is a corepressor in the lac operon. Introns have no detectable functions. Which of the following is the process of getting oxygen from the environment to the tissues of the body? Total word count: Test yourself. Join Study Groups. Create your own study plan. Join live cram sessions. Live student success coach. Top Biology Educators Marissa M. Bridgewater State University.

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If a particular operon enc…. Thus, in the case of the lac operon, for transcription to occur, lactose must be present removing the lac repressor protein and glucose levels must be depleted allowing binding of an activating protein.

When glucose levels are high, there is catabolite repression of operons encoding enzymes for the metabolism of alternative substrates. See Table 1 for a summary of the regulation of the lac operon. Figure 6. In prokaryotes, there are also several higher levels of gene regulation that have the ability to control the transcription of many related operons simultaneously in response to an environmental signal. A group of operons all controlled simultaneously is called a regulon.

When sensing impending stress, prokaryotes alter the expression of a wide variety of operons to respond in coordination. They do this through the production of alarmones , which are small intracellular nucleotide derivatives. Alarmones change which genes are expressed and stimulate the expression of specific stress-response genes. The use of alarmones to alter gene expression in response to stress appears to be important in pathogenic bacteria.

On encountering host defense mechanisms and other harsh conditions during infection, many operons encoding virulence genes are upregulated in response to alarmone signaling. Knowledge of these responses is key to being able to fully understand the infection process of many pathogens and to the development of therapies to counter this process.

Although most gene expression is regulated at the level of transcription initiation in prokaryotes, there are also mechanisms to control both the completion of transcription as well as translation concurrently. Since their discovery, these mechanisms have been shown to control the completion of transcription and translation of many prokaryotic operons. Because these mechanisms link the regulation of transcription and translation directly, they are specific to prokaryotes, because these processes are physically separated in eukaryotes.

Beyond the transcriptional repression mechanism already discussed, attenuation also controls expression of the trp operon in E. The trp operon regulatory region contains a leader sequence called trpL between the operator and the first structural gene, which has four stretches of RNA that can base pair with each other in different combinations. However, when an antiterminator stem-loop forms, this prevents the formation of the terminator stem-loop, so RNA polymerase can transcribe the structural genes.

Figure 7. Click to view a larger image. When tryptophan is plentiful, translation of the short leader peptide encoded by trpL proceeds, the terminator loop between regions 3 and 4 forms, and transcription terminates.

When tryptophan levels are depleted, translation of the short leader peptide stalls at region 1, allowing regions 2 and 3 to form an antiterminator loop, and RNA polymerase can transcribe the structural genes of the trp operon. A riboswitch may bind to a small intracellular molecule to stabilize certain secondary structures of the mRNA molecule. The binding of the small molecule determines which stem-loop structure forms, thus influencing the completion of mRNA synthesis and protein synthesis.

Figure 8. Click for a larger image. Riboswitches found within prokaryotic mRNA molecules can bind to small intracellular molecules, stabilizing certain RNA structures, influencing either the completion of the synthesis of the mRNA molecule itself left or the protein made using that mRNA right.

Although the focus on our discussion of transcriptional control used prokaryotic operons as examples, eukaryotic transcriptional control is similar in many ways. As in prokaryotes, eukaryotic transcription can be controlled through the binding of transcription factors including repressors and activators.

Interestingly, eukaryotic transcription can be influenced by the binding of proteins to regions of DNA, called enhancers , rather far away from the gene, through DNA looping facilitated between the enhancer and the promoter Figure 9. Overall, regulating transcription is a highly effective way to control gene expression in both prokaryotes and eukaryotes. However, the control of gene expression in eukaryotes in response to environmental and cellular stresses can be accomplished in additional ways without the binding of transcription factors to regulatory regions.

Figure 9. In eukaryotes, an enhancer is a DNA sequence that promotes transcription. Each enhancer is made up of short DNA sequences called distal control elements. Activators bound to the distal control elements interact with mediator proteins and transcription factors.

Two different genes may have the same promoter but different distal control elements, enabling differential gene expression. In eukaryotes, the DNA molecules or associated histones can be chemically modified in such a way as to influence transcription; this is called epigenetic regulation. Methylation of certain cytosine nucleotides in DNA in response to environmental factors has been shown to influence use of such DNA for transcription, with DNA methylation commonly correlating to lowered levels of gene expression.

Additionally, in response to environmental factors, histone proteins for packaging DNA can also be chemically modified in multiple ways, including acetylation and deacetylation, influencing the packaging state of DNA and thus affecting the availability of loosely wound DNA for transcription. These chemical modifications can sometimes be maintained through multiple rounds of cell division, making at least some of these epigenetic changes heritable.

Although Travis survived his bout with necrotizing fasciitis, he would now have to undergo a skin-grafting surgery, followed by long-term physical therapy. Based on the amount of muscle mass he lost, it is unlikely that his leg will return to full strength, but his physical therapist is optimistic that he will regain some use of his leg.

At the CDC, the strain of group A strep isolated from Travis was analyzed more thoroughly for methicillin resistance. Methicillin resistance is genetically encoded and is becoming more common in group A strep through horizontal gene transfer.

In necrotizing fasciitis, blood flow to the infected area is typically limited because of the action of various genetically encoded bacterial toxins. This is why there is typically little to no bleeding as a result of the incision test. Nevertheless, intravenous antibiotic therapy was warranted to help minimize the possible outcome of sepsis, which is a common outcome of necrotizing fasciitis.

Through genomic analysis by the CDC of the strain isolated from Travis, several of the important virulence genes were shown to be encoded on prophages, indicating that transduction is important in the horizontal gene transfer of these genes from one bacterial cell to another. An operon of genes encoding enzymes in a biosynthetic pathway is likely to be which of the following?

An operon encoding genes that are transcribed and translated continuously to provide the cell with constant intermediate levels of the protein products is said to be which of the following?

Skip to main content. Mechanisms of Microbial Genetics. Search for:. Gene Regulation: Operon Theory Learning Objectives Compare inducible operons and repressible operons Describe why regulation of operons is important. What types of regulatory molecules are there? Watch this video to learn more about the trp operon.

Watch an animated tutorial about the workings of lac operon here. Think about It What affects the binding of the trp operon repressor to the operator?

How and when is the behavior of the lac repressor protein altered? In addition to being repressible, how else is the lac operon regulated? Think about It What is the name given to a collection of operons that can be regulated as a group?