question

The role of a metabolite that controls a repressible operon is to

answer

bind to the repressor protein and activate it

question

The tryptophan operon is a repressible operon that is

answer

turned off whenever tryptophan is added to the growth medium

question

Which of the following is a protein produced by a regulatory gene?

answer

repressor

question

A lack of which molecule would result in the cell's inability to "turn off" genes?

answer

corepressor

question

Which of the following, when taken up by the cell, binds to the repressor so that the repressor no longer binds to the operator?

answer

inducer

question

Most repressor proteins are allosteric. Which of the following binds with the repressor to alter its conformation

answer

inducer

question

A mutation that inactivates the regulatory gene of a repressible operon in an E. coli cell would result in

answer

continuous transcription of the structural gene controlled by that regulator.

question

The lactose operon is likely to be transcribed when

answer

the cyclic AMP and lactose levels are both high within the cell.

question

Transcription of the structural genes in an inducible operon

answer

starts when the pathway's substrate is present.

question

For a repressible operon to be transcribed, which of the following must occur?

answer

RNA polymerase must bind to the promoter, and the repressor must be inactive.

question

Allolactose, an isomer of lactose, is formed in small amounts from lactose. An E. coli cell is presented for the first time with the sugar lactose (containing allolactose) as a potential food source. Which of the following occurs when the lactose enters the cell?

answer

Allolactose binds to the repressor protein.

question

Altering patterns of gene expression in prokaryotes would most likely serve the organism's survival in which of the following ways?

answer

allowing the organism to adjust to changes in environmental conditions

question

In response to chemical signals, prokaryotes can do which of the following?

answer

alter the level of production of various enzymes

question

If glucose is available in the environment of E. coli, the cell responds with a very low concentration of cAMP. When the cAMP increases in concentration, it binds to CAP. Which of the following would you expect to be a measurable effect?

answer

increased concentrations of sugars such as arabinose in the cell

question

In positive control of several sugar-metabolism-related operons, the catabolite activator protein (CAP) binds to DNA to stimulate transcription. What causes an increase in CAP?

answer

decrease in glucose and increase in cAMP

question

There is a mutation in the repressor that results in a molecule known as a super-repressor because it represses the lac operon permanently. Which of these would characterize such a mutant?

answer

It cannot bind to the inducer.

question

Which of the following mechanisms is (are) used to coordinate the expression of multiple, related genes in eukaryotic cells?

answer

Genes are organized into clusters, with local chromatin structures influencing the expression of all the genes at once.

question

If you were to observe the activity of methylated DNA, you would expect it to

answer

have turned off or slowed down the process of transcription.

question

Genomic imprinting, DNA methylation, and histone acetylation are all examples of

answer

epigenetic phenomena

question

When DNA is compacted by histones into 10-nm and 30-nm fibers, the DNA is unable to interact with proteins required for gene expression. Therefore, to allow for these proteins to act, the chromatin must constantly alter its structure. Which processes contribute to this dynamic activity?

answer

methylation and phosphorylation of histone tails

question

Two potential devices that eukaryotic cells use to regulate transcription are

answer

DNA methylation and histone modification.

question

During DNA replication

answer

methylation of the DNA is maintained because methylation enzymes act at DNA sites where one strand is already methylated and thus correctly methylates daughter strands after replication.

question

In eukaryotes, general transcription factors

answer

bind to other proteins or to a sequence element within the promoter called the TATA box.

question

Steroid hormones produce their effects in cells by

answer

binding to intracellular receptors and promoting transcription of specific genes.

question

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

answer

other transcription factors

question

26) Gene expression might be altered at the level of post-transcriptional processing in eukaryotes rather than prokaryotes because of which of the following?

answer

Eukaryotic exons may be spliced in alternative patterns.

question

27) Which of the following experimental procedures is most likely to hasten mRNA degradation in a eukaryotic cell?

answer

removal of the 5' cap

question

Which of the following is most likely to have a small protein called ubiquitin attached to it?

answer

a cyclin that usually acts in G₁, now that the cell is in G₂

question

In prophase I of meiosis in female Drosophila, studies have shown that there is phosphorylation of an amino acid in the tails of histones of gametes. A mutation in flies that interferes with this process results in sterility. Which of the following is the most likely hypothesis?

answer

Histone tail phosphorylation prohibits chromosome condensation.

question

The phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to an introduced double-stranded RNA is called

answer

RNA interference.

question

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 was much smaller than they had expected. Which of the following could account for most of the rest?

answer

non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function

question

Among the newly discovered small noncoding RNAs, one type reestablishes methylation patterns during gamete formation and block expression of some transposons. These are known as

answer

piRNA.

question

Which of the following best describes siRNA?

answer

a short double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA

question

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?

answer

targeting siRNAs to disable the expression of an allele associated with autosomal dominant disease

question

Which of the following describes the function of an enzyme known as Dicer?

answer

It trims small double-stranded RNAs into molecules that can block translation.

question

In a series of experiments, the enzyme Dicer has been inactivated in cells from various vertebrates so that the centromere is abnormally formed from chromatin. Which of the following is most likely to occur?

answer

Centromeres will be euchromatic rather than heterochromatic and the cells will soon die in culture.

question

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

answer

Changes in technology as well as our ability to determine how much of the DNA is expressed have now made this possible

question

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 might best give you an answer?

answer

You measure the quantity of the appropriate pre-mRNA in various cell types and find they are all the same.

question

In humans, the embryonic and fetal forms of hemoglobin have a higher affinity for oxygen than that of adults. This is due to

answer

nonidentical genes that produce different versions of globins during development.

question

The fact that plants can be cloned from somatic cells demonstrates that

answer

differentiated cells retain all the genes of the zygote.

question

In animals, embryonic stem cells differ from adult stem cells in that

answer

embryonic stem cells are totipotent, and adult stem cells are pluripotent.

question

What is considered to be the first evidence of differentiation in the cells of an embryo?

answer

the occurrence of mRNAs for the production of tissue-specific proteins

question

Embryonic lethal mutations result in

answer

phenotypes that are never born/hatched.

question

Your brother has just purchased a new plastic model airplane. He places all the parts on the table in approximately the positions in which they will be located when the model is complete. His actions are analogous to which process in development?

answer

pattern formation

question

The product of the bicoid gene in Drosophila provides essential information about

answer

the anterior-posterior axis

question

If a Drosophila female has a homozygous mutation for a maternal effect gene,

answer

all of her offspring will show the mutant phenotype, regardless of their genotype.

question

Mutations in which of the following genes lead to transformations in the identity of entire body parts?

answer

homeotic genes

question

Which of the following genes map out the basic subdivisions along the anterior-posterior axis of the Drosophila embryo?

answer

segmentation genes

question

Gap genes and pair-rule genes fall into which of the following categories?

answer

segmentation genes

question

The bicoid gene product is normally localized to the anterior end of the embryo. If large amounts of the product were injected into the posterior end as well, which of the following would occur?

answer

Anterior structures would form in both sides of the embryo.

question

What do gap genes, pair-rule genes, segment polarity genes, and homeotic genes all have in common?

answer

Their products act as transcription factors.

question

Which of the following statements describes proto-oncogenes?

answer

They can code for proteins associated with cell growth.

question

Which of the following is characteristic of the product of the p53 gene?

answer

It is an activator for other genes.

question

Tumor-suppressor genes

answer

can encode proteins that promote DNA repair or cell-cell adhesion.

question

BRCA1 and BRCA2 are considered to be tumor-suppressor genes because

answer

their normal products participate in repair of DNA damage.

question

The cancer-causing forms of the Ras protein are involved in which of the following processes?

answer

relaying a signal from a growth factor receptor

question

Forms of the Ras protein found in tumors usually cause which of the following?

answer

growth factor signaling to be hyperactive

question

A genetic test to detect predisposition to cancer would likely examine the APC gene for involvement in which type(s) of cancer?

answer

colorectal only

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