Ch 18 learning curve and quiz questions

The lactose operon is an example of positive regulation by an inducer whose function is modulated by a repressor TF

False

The miRNA-RISC-mRNA complex enhances the translation efficiency of the mRNA transcript TF

False

Which answer choice is an accurate description of events leading to the lytic pathway following viral infection in a bacterium?

When bacterial cells are grown in favorable conditions, proteases degrade cII, cro represses cI transcription, which leads to the expression of all genes needed for synthesis of phage components and lysis.

Consider the figure shown. Which type of mutation could block the lysogenic pathway and cause a phage to follow the lytic pathway?

a mutation that blocks the function of the PR promoter

In a bacteriophage that undergoes lysogeny, the viral DNA is:

in the bacterial DNA

For the lactose operon, lactose is a(n):

inducer

Patau Syndrome is a severe birth defect caused by an extra copy of chromosome 13 (trisomy 13). Which procedure, if done early in development, could counteract the effect of having an extra copy of chromosome 13 and potentially be a treatment for Patau Syndrome?

insertion of a copy of the Xist gene onto one of the three copies of chromosome 13

Insulin is needed to regulate sugar levels in the blood. While every cell in the body contains genes to produce insulin, it is only produced by a specialized subset of cells in the pancreas. Therefore:

mechanisms of gene regulation promote insulin expression in the specialized pancreatic cells and prevent insulin expression in all other cells

When a group of functionally related genes located next to one another along the bacterial DNA is transcribed as a single molecule of mRNA, that mRNA is said to be:

polycistronic

An operon is a:

region of DNA consisting of the promoter, the operator, and coding sequences for structural proteins

MicroRNA is a type of: transfer RNA. splicing RNA. messenger RNA. regulatory RNA. ribosomal RNA.

regulatory RNA

A mutation in Gene X is caused by a small deletion that reduces the size of the mRNA. This mutation does not disrupt translation, but causes the protein to be produced in the wrong location in the cell. Which region of the mRNA must be affected by this mutation?

the 5' UTR

Which of the events occurs during RNA processing?

the addition of a nucleotide cap to the 5' end and a poly(A) tail to the 3' end of the newly transcribed RNA

In prokaryotes:

the translation of an mRNA can begin even before transcription is completed

Histone modification occurs only during early development TF

False

Which of the answer choices is/are an example of post-translational modification? -addition of one or more sugar molecules to the side chains of some amino acids -marking proteins for enzymatic destruction -addition of a phosphate group to the side chains of amino acids such as serine, threonine, or tyrosine -assistance by chaperons in folding of newly translated proteins -All of these choices are correct.

All

The following are two genotypes of the lactose operon in E. coli: I. I+ P+ Oc Z+ Y+ II. I- P+ O+ Z+ Y+ Do either of these genotypes produce β-galactosidase and permease in the absence of lactose?

Both produce β-galactosidase and permease

Primary RNA transcripts never splice differently so that the same primary transcript generated from a single gene can give rise only to one kind of processed mRNA transcript and thus to one kind of protein TF

False

Which statement accurately describes DNA methylation?

Methyl groups are most often added to cytosines adjacent to guanine bases in or near the promoter sequence, decreasing the probability of gene expression

Transcription is repressed when the cytosines within CpG islands in genes' promoters are methylated. Which answer option could account for this effect on gene expression?

Methylated cytosines bind to enzymes that cause the removal of acetyl groups from histones, causing chromatin to coil more tightly.

Which answer option accurately describes events in the movement of mRNA from the nucleus to the cytoplasm?

Processed mRNA transcripts are recognized and transported to the cytoplasm through nuclear pores

A particular human gene is expressed in both the heart and the lung. However, analysis of the products of this gene show that the protein encoded by this gene is larger in lung tissue than in heart tissue, even though the mRNAs in both of those tissues are the same size. Which answer option could have caused the size difference in the proteins, but not the mRNAs, between the heart and lung?

RNA editing that occurs in the heart but not the lung

A particular human gene is expressed in both the heart and the lung. However, analysis of the products of this gene shows that both the mRNA and the protein encoded by this gene are larger in lung tissue than in heart tissue. Which answer option could have caused these differences in protein and mRNA between the heart and lung?

RNA splicing that includes particular exons in the gene's mRNA in the lung but not the heart

Active β-galactosidase enzyme is observed only in E. coli growing in the presence of lactose. One hypothesis is that the enzyme is always being produced but is produced in an unstable form that breaks down rapidly in the absence of lactose (hypothesis 1). A second hypothesis is that the enzyme is stable but is produced only in the presence of lactose (hypothesis 2). An experiment was performed to test these hypotheses. A culture of growing cells was exposed to lactose, which was later removed. The amount of β-galactosidase present in the culture during the course of the experiment was measured. The data are shown in the following graph. Which statement is a conclusion that can be obtained from these experimental data?

Synthesis of β-galactosidase is turned on when lactose is added and turned off when lactose is removed, in support of hypothesis 2

What happens when the Xist gene from an X chromosome is inserted into an autosome?

The autosome with Xist is inactivated like an X chromosome

The following are two genotypes of the lactose operon in E. coli: I. I+ P- Oc Z+ Y+ II. I- P+ O+ Z+ Y+ Do either of these genotypes produce β-galactosidase and permease in the presence of lactose?

The first one does not produce β-galactosidase and permease, the second one does.

Anhidrosis Ectodermal Dysplasia is caused by a single gene mutation that affects the ability of sweat glands to function properly. Human males affected by this mutation cannot produce sweat properly anywhere on their body, whereas females with this condition are affected in a mosaic pattern in which some patches of skin cannot produce sweat while other areas can. Which answer option could account for this mosaicism in females but not males?

The gene causing this disorder is located on the X chromosome

What would be the consequence of a mutation in the lacI repressor gene that produces a repressor protein that is able to bind the operator, but is not able to bind allolactose?

The lacZ and lacY genes would not be expressed even when lactose is present

MicroRNA (miRNA) can affect gene expression in three ways: by causing chromatin remodeling, by causing RNA degradation, or by causing translation inhibition. In some tissues, Gene X is regulated by the expression of an miRNA. In other tissues, the miRNA affecting Gene X is not expressed. Analysis of the gene's RNA and protein products show the following:

The miRNA is affecting the chromatin structure of Gene X

Which statement about regulation of translation is correct? -The 5' UTR sequence does not affect the efficiency of translation initiation. -The translation initiation complex scans for a TAC codon near the 5' cap. -One of the key variables for influencing efficient translation is the sequence of nucleotides flanking the first GUG codon. -Translation initiation complexes recognize and bind to the 5' cap. -Regulation of translation does not depend on sequences in the 3' UTR or the poly(A) tail.

Translation initiation complexes recognize and bind to the 5' cap

A functional RISC targets RNA molecules containing one or more regions that can undergo base pairing with the small regulatory RNA incorporated in the RISC. TF

True

After small regulatory RNAs are transcribed and processed, specialized enzymes cleave the RNAs to double-stranded fragments that are typically around 20-25 nucleotides long. TF

True

Depending on the type of small regulatory RNA, the RNA sequence in the RISC, and the particular type of RISC, the small regulatory RNA may result in chromatin remodeling, degradation of RNA transcripts, or inhibition of mRNA translation. TF

True

In bacteriophage that can undergo the lytic cycle or lysogeny, an excess of cro protein is associated with the lytic cycle. TF

True

Methylated cytosines are often observed in CpG islands near genes that are repressed TF

True

Methylated cytosines are often observed in CpG islands near genes that are repressed. TF

True

Unlike processing of the primary transcript, RNA editing occurs at the level of mRNA. TF

True

In domestic cats, the coat-color pattern known as calico is an example of: epigenetic regulation. dosage compensation. X-inactivation. gene regulation at the level of the chromosome. All of these choices are correct

all

Which condition would cause constitutive expression of lacZ and lacY? mutations in lacI that prevent the repressor from binding to lactose high levels of lactose and low levels of glucose mutations in lacO that prevent it from binding to the repressor All of these choices are correct.

all

Prion protein (PrP) can cause mad cow disease when it folds improperly and forms protein aggregates. Which answer option could cause misfolding of PrP?

changes affecting chaperone proteins that bind to PrP

The complex of DNA, RNA, and associated proteins that gives shape to the chromosome is called:

chromatin

In RNA editing:

enzymes change the base sequence of the primary transcript and therefore the protein for which it codes.

Modifications of bases, changes to histones, and alterations in chromatin structure that regulate gene expression are said to be:

epigenetic

In prokaryotes, when the promoter is bound to the repressor, the operator recruits the RNA polymerase complex and transcription of polycistronic RNA occurs TF

false

The lactose operon is an example of positive regulation by an inducer whose function is modulated by a repressor. TF

false

Primary RNA transcripts from a gene are sometimes spliced in different ways and can produce multiple different mRNAs TF

true