Question 1

You are given an experimental problem involving control of a gene's expression in the embryo of a particular species.One of your first questions is whether the gene's expression is controlled at the level of transcription or translation.Which of the following experiments might best give you an answer?

Accepted Answer

Measuring the quantity of pre-mRNA can help determine if transcription is occurring at similar levels across different cell types, indicating control at the transcription level.

Question 2

Which of the following statements best describes siRNA?

Accepted Answer

siRNA (short interfering RNA) is a short double-stranded RNA molecule that can bind to mRNA (messenger RNA) and block gene expression by leading to its degradation or preventing its translation into protein. It is typically about 20-25 nucleotides long and is generated by the cleavage of longer double-stranded RNA precursors by the enzyme Dicer. RNA interference (RNAi) mediated by siRNA has become a widely used tool in gene function and drug target discovery studies.

Question 3

Among the newly discovered small noncoding RNAs,one type reestablishes methylation patterns during gamete formation and blocks expression of some transposons.
What are these types of RNA called?

Accepted Answer

The type of RNA mentioned in the description is piRNA (Piwi-interacting RNA), which is largely involved in silencing transposons during gamete formation and protecting the genome by reestablishing epigenetic marks. MiRNA (microRNA) and siRNA (small interfering RNA) also play a role in gene regulation, but their functions differ from piRNA. snRNA (small nuclear RNA) is involved in splicing and processing of pre-mRNA in the nucleus.

Question 4

In the microarray shown in the figure above,if you were searching for genes whose expression was inhibited by hormone treatment,you would search for sequences spotted on the array that showed what level of fluorescence?

Accepted Answer

If the genes' expression is inhibited by hormone treatment, the level of fluorescence should be lower than the control sample (which is represented by the red spots on the microarray). Therefore, there should be no or very little fluorescence in the corresponding spots on the microarray.

Question 5

Researchers are looking for better treatments for breast cancer.For a particular DNA microarray assay (DNA chip),cDNA has been made from the mRNAs of a dozen patients' breast tumor biopsies.What would the researchers be looking for in this type of assay?

Accepted Answer

In this type of assay, researchers would be looking for a pattern shared among some or all of the samples that indicates gene expression differing from control samples. This would help them identify genes that may be involved in breast cancer development and could potentially be targeted for treatment. Options A, B, and D are not necessarily the main objectives of this type of assay.

Question 6

Which of the following results can a DNA microarray assay detect or identify?

Accepted Answer

DNA microarray assays can be used to compare the expression of many or even all of the genes in a genome at once. They do not identify the function of any gene in a genome, introduce entire genomes into bacterial cells, or assemble physical maps of the genome in a short time.

Question 7

One way scientists hope to use the recent knowledge gained about noncoding RNAs lies with the possibilities for their use in medicine.Of the following scenarios for future research,which would you expect to gain most from RNAs?

Accepted Answer

siRNAs can be used to specifically target and silence the expression of alleles associated with autosomal dominant diseases, where a single copy of the mutant allele can cause disease.

Question 8

In a genome-wide expression study using a DNA microarray assay,what is each spot used to detect?

Accepted Answer

Each spot on a DNA microarray is used to detect the expression of a specific gene by a cell. The microarray contains probes that are complementary to specific genes, and when the probes bind to their target genes, it indicates that the gene is being expressed. This allows researchers to analyze the expression levels of thousands of genes simultaneously and identify patterns of gene expression that are associated with different biological processes or diseases.

Question 9

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome.If she moves the regulatory gene (lac I),along with its promoter,to a position some several thousand base pairs away from its normal position,which would you expect to occur?

Accepted Answer

The lac operon is designed to function with its components spread out across the genome. Moving the lacI gene and its promoter does not inherently disrupt the production or function of the repressor protein; it can still be made, bind to the operator, and interact with the inducer as long as the regulatory sequences necessary for its expression and function are intact and accessible.

Question 10

Which of the following techniques involves reverse transcriptase,PCR amplification,and gel electrophoresis?

Accepted Answer

Reverse transcriptase is used to convert RNA to cDNA, which is then PCR amplified and run on a gel to visualize the product. This is known as RT-PCR. DNA microarray assays involve hybridizing labeled nucleic acids to a chip containing many probes, in situ hybridization involves using a labeled probe to detect nucleic acids in situ, and nucleic acid hybridization involves annealing complementary strands of nucleic acids. None of these methods involve the use of reverse transcriptase and PCR amplification.

Question 11

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome.If she moves the promoter for the lac operon to the region between the beta galactosidase (lacZ)gene and the permease (lacY)gene,which of the following results would be likely?

Accepted Answer

The answer of Suppose an experimenter becomes proficient with a...

Question 12

Transcription factors in eukaryotes usually have DNA-binding domains as well as other domains that are specific for binding other molecules.In general,which of the following would you expect many of them to be able to bind?

Accepted Answer

Transcription factors often interact with other transcription factors to regulate gene expression. Therefore, it is likely that many of them have domains specifically designed for binding to other transcription factors. While some transcription factors may also be able to bind repressors or protein-based hormones, these types of molecules are not as universally relevant to transcription factor function as other transcription factors themselves. tRNA is also unlikely to be a common target of transcription factor binding, as it is not directly related to regulating gene expression.

Question 13

At the beginning of this century there was a general announcement regarding the sequencing of the human genome and the genomes of many other multicellular eukaryotes.There was surprise expressed by many that the number of protein-coding sequences in the human genome was much smaller than had been expected.Which of the following statements would describe most of the rest of the DNA in the human genome?

Accepted Answer

Most of the rest of the DNA in the human genome is non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function, such as regulatory RNAs and microRNAs. This non-coding DNA is now recognized as having important functions in gene regulation and other cellular processes. The term "junk" DNA is no longer accurate as it implies a lack of function.

Question 14

Which of the following statements describes one of the functions of the protein called ubiquitin?

Accepted Answer

Ubiquitin attaches to proteins that are marked for destruction in the cell, leading them to be recognized and degraded by the proteasome. This is an important regulatory function in maintaining protein levels and preventing the accumulation of damaged or misfolded proteins.

Question 15

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture.In one set of experiments she succeeded in decreasing methylation of histone tails.Which of the following results would she most likely see?

Accepted Answer

Decreasing methylation of histone tails would likely result in decreased chromatin condensation, as methylation typically promotes a more condensed chromatin structure. The other options are less likely to be directly affected by changes in histone methylation.

Question 16

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome.If she moves the operator to the far end of the operon,past the transacetylase (lacA)gene,which of the following results would likely occur when the cell is exposed to lactose?

Accepted Answer

Moving the operator past the transacetylase (lacA) gene would result in the three genes of the operon being transcribed continuously, as the repressor would no longer be able to bind to the operator and block transcription. This would result in the continuous expression of lactose-utilizing enzymes, even in the absence of lactose.

Question 17

Since Watson and Crick described the structure of DNA in 1953,which of the following statements might best explain why the function of small RNAs is still being explained?

Accepted Answer

Changes in technology, such as RNA sequencing and genome-wide analysis, have allowed us to better understand the functions of small RNAs. Additionally, our ability to determine gene expression patterns has aided in discovering the regulatory roles of small RNAs. While small RNAs have evolved since the discovery of DNA's structure, this alone does not fully explain why their functions are still being explained. Watson and Crick's focus was on DNA, but they did suggest some possible functions for RNA, such as messenger RNA. The sequencing of the human genome was a significant milestone, but it alone did not allow for the study of small RNAs; further advancements were necessary.

Question 18

Gene expression can be blocked by a process called RNA interference.Which of the following molecules is involved in this process?

Accepted Answer

RNA interference involves small interfering RNAs (siRNAs) that bind to complementary mRNA sequences and block their expression. rRNAs and tRNAs are not involved in this process, and while mRNA is the target of siRNA action, it is not directly involved in the process of RNA interference.

Question 19

Which of the following processes do steroid hormones carry out to produce their effects?

Accepted Answer

Steroid hormones bind to receptors inside the cell, and the resulting hormone-receptor complex acts as a transcription factor to promote the transcription of specific genes. This transcriptional regulation ultimately leads to the production of proteins that mediate the hormone's effects.

Question 20

Gene expression might be altered based on post-transcriptional processing in eukaryotes rather than prokaryotes.Which of the following statements describes this difference?

Accepted Answer

Eukaryotic exons may be spliced in alternative patterns, which allows for the production of multiple proteins from a single gene.

Quiz 15: Regulation of Gene Expression