Operon Model Trivia Quiz Ch 18

The operon model attempts to explain the coordinated control of gene expression in bacteria. In bacteria, genes are often organized into operons, which are clusters of genes that are transcribed together as a single mRNA molecule. The operon model describes how the expression of these genes is regulated by a common regulatory region called the operator. This allows bacteria to control the expression of multiple genes involved in a specific biological process or pathway in a coordinated manner.

A repressor can inhibit transcription by binding to the DNA and preventing the binding of positively acting transcription factors. This binding prevents the formation of the transcription initiation complex and blocks the RNA polymerase from starting transcription. Therefore, the presence of a repressor can effectively shut down gene expression by inhibiting transcription.

The correct answer is terminator. The terminator is a site in the DNA that is located near the end of the final exon. It encodes an RNA sequence that determines the 3' end of the transcript. The terminator is responsible for signaling the end of transcription and helps in the termination of RNA synthesis.

A mutation in the promoter region of DNA could affect the binding of RNA polymerase to the DNA. The promoter is a specific sequence of DNA that acts as a binding site for RNA polymerase, which is an enzyme responsible for initiating transcription. If there is a mutation in the promoter region, it could alter the sequence and disrupt the binding of RNA polymerase, leading to a decrease or loss of transcription of the gene or genes regulated by that promoter.

In order for a repressible operon to be transcribed, RNA polymerase must bind to the promoter, which is the region of DNA where transcription begins. Additionally, the repressor protein, which normally binds to the operator region of the operon to prevent transcription, must be inactive. This allows RNA polymerase to proceed with transcription and produce the necessary mRNA.

Altering patterns of gene expression in prokaryotes allows the organism to adjust to changes in environmental conditions. This is because prokaryotes can regulate which genes are expressed and when, allowing them to respond to different environmental cues. By adjusting gene expression, prokaryotes can produce the necessary proteins and enzymes to adapt to changes in temperature, nutrient availability, or other environmental factors. This flexibility in gene expression enables prokaryotes to survive and thrive in various conditions and increase their chances of survival.

The tryptophan operon is a repressible operon, meaning that it is usually turned on and producing enzymes involved in tryptophan synthesis. However, when tryptophan is added to the growth medium, it acts as a co-repressor and binds to the repressor protein, forming an active repressor complex. This complex then binds to the operator region of the operon, preventing transcription of the genes involved in tryptophan synthesis. Therefore, the operon is turned off whenever tryptophan is added to the growth medium.

A repressor is a protein that is produced by a regulatory gene and is responsible for inhibiting the expression of genes. It binds to the operator region of the DNA, preventing the RNA polymerase from transcribing the genes downstream. This allows the repressor to control the expression of genes by blocking their transcription. Therefore, the given statement suggests that the protein produced by the regulatory gene is a repressor.

Eukaryotic cells regulate transcription through various mechanisms, including DNA methylation and histone acetylation. DNA methylation involves the addition of a methyl group to the DNA molecule, which can lead to gene silencing and decreased transcription. Histone acetylation, on the other hand, involves the addition of an acetyl group to histone proteins, which relaxes the chromatin structure and allows for increased transcription. Therefore, DNA methylation and histone acetylation are two potential devices that eukaryotic cells use to regulate transcription.

The inducer is a molecule that, when taken up by the cell, binds to the repressor protein. This binding prevents the repressor from binding to the operator, which is a DNA sequence that controls the expression of genes in an operon. By binding to the repressor, the inducer allows the RNA polymerase to access the promoter region and initiate gene transcription. Therefore, the presence of the inducer molecule leads to the activation of gene expression in the operon.

Eukaryotic exons may be spliced in alternative patterns, which means that different combinations of exons can be joined together to form mature mRNA. This alternative splicing allows for the production of multiple protein isoforms from a single gene, increasing the complexity and diversity of gene expression in eukaryotes. In contrast, prokaryotes do not undergo alternative splicing and their genes are generally expressed as a single continuous mRNA sequence. Therefore, post-transcriptional processing, such as alternative splicing, is more likely to alter gene expression in eukaryotes rather than prokaryotes.

Proto-oncogenes are genes that have the potential to become oncogenes, which are genes that can cause cancer. They are not introduced to a cell by retroviruses or produced by somatic mutations induced by carcinogenic substances. Their normal function is not to suppress tumor growth, but rather to regulate normal cell growth and division. Proto-oncogenes can code for proteins that are involved in cell growth, and when mutated or overexpressed, they can lead to uncontrolled cell growth and the development of cancer. They are not underexpressed in cancer cells, as their abnormal activation is often associated with cancer development.

Steroid hormones are able to produce their effects in cells by binding to intracellular receptors and promoting the transcription of specific genes. This binding activates the receptors, which then act as transcription factors to bind to specific regions of DNA and initiate the process of gene transcription. This leads to the production of specific proteins that mediate the hormone's effects on the target cells.

An activator is a protein that binds to a specific site in the DNA, known as an enhancer, which is located far from the promoter region. This binding event stimulates the transcription process, leading to increased gene expression. Unlike a repressor, which inhibits transcription, an activator enhances or activates gene expression. Therefore, an activator is the most suitable option to explain the given statement.

The ras protein is a key regulator of cell growth and division. When forms of the ras protein are found in tumors, they often have mutations that cause the protein to be hyperactive. This means that the signaling pathways for growth factors, which normally control cell growth and division, become overactive. As a result, the cells in the tumor can grow and divide uncontrollably, leading to the development and progression of the tumor.

A lack of corepressor would result in the inability of the cell to "turn off" genes. Corepressors are small molecules that bind to repressor proteins and enable them to bind to DNA, preventing the transcription of specific genes. Without corepressors, repressor proteins would not be able to effectively bind to DNA and inhibit gene expression, leading to the inability of the cell to "turn off" genes.

The correct answer is that the metabolite binds to the repressor protein and activates it. This means that the metabolite molecule interacts with the repressor protein, causing a conformational change that allows the repressor protein to bind to the operator region of the operon. By binding to the operator, the repressor prevents RNA polymerase from attaching to the promoter region and initiating transcription. Therefore, the metabolite indirectly controls the expression of the operon by activating the repressor protein.

Prokaryotes can alter the level of production of various enzymes in response to chemical signals. This means that they can regulate the amount of enzymes they produce based on the signals they receive. This allows them to adapt and respond to changes in their environment, ensuring that they have the necessary enzymes for specific metabolic processes. By adjusting enzyme production, prokaryotes can optimize their cellular functions and survive in different conditions.

When glucose is available in the environment of E.coli, the cell responds by producing a low concentration of cAMP. However, when cAMP levels increase, it binds to CAP (catabolite activator protein), which leads to the activation of certain genes involved in sugar metabolism. This activation would result in an increased concentration of sugars, such as arabinose, in the cell. Therefore, the measurable effect would be an increased concentration of sugars like arabinose in the cell.

If the researcher is successful in increasing phosphorylation of amino acids adjacent to methylated amino acids in histone tails, it is likely that this modification will lead to decreased chromatin concentration. Phosphorylation and methylation are known to affect the structure and packaging of chromatin, with phosphorylation generally associated with more relaxed chromatin and methylation associated with more condensed chromatin. Therefore, increasing phosphorylation in this context would likely result in a decrease in chromatin concentration.

By decreasing the amount of methylation enzymes in the embryonic stem cells, the researcher is likely to disrupt the normal process of DNA methylation, which plays a crucial role in embryonic development. Methylation is involved in regulating gene expression and maintaining the stability of the genome. Therefore, a decrease in methylation enzymes could lead to abnormalities in mouse embryos as the normal development process is disrupted.

The product of the p53 gene is an activator for other genes. This means that it plays a role in regulating the expression of other genes in the cell. It can bind to specific DNA sequences and activate the transcription of target genes, which can then lead to various cellular responses such as DNA repair, cell cycle arrest, or apoptosis. By acting as an activator for other genes, the p53 gene product helps maintain the integrity of the genome and regulate cell growth and division.

If the researcher increases methylation of C nucleotides in a mammalian system, she would most likely see the inactivation of the selected genes. Methylation of DNA can lead to gene silencing or inactivation, as it prevents the binding of transcription factors and other proteins necessary for gene expression. This can result in the selected genes being turned off or not functioning properly.

When the researcher decreases methylation of histone tails, it is likely to result in increased chromatin condensation. Methylation of histone tails is associated with a more open chromatin structure, allowing for gene expression. When methylation is decreased, the chromatin becomes more condensed, leading to a tighter packing of DNA and potentially inhibiting gene expression. Therefore, the most likely result of decreasing methylation of histone tails would be increased chromatin condensation.