BSC 120 CH. 13 study questions

When replication starts, an origin of replication forms, consisting of two replication fork(s)moving in opposite directions. DNA double helix is separated into single strands by the enzyme DNA helicase. Newly-exposed, unreplicated DNA is protected by single-strand binding protein. Short segments of RNA are synthesized, called RNA primers. The enzyme that synthesizes the short segments of RNA is called a primase. The short RNA segments provide a free 3' OH for replication. New DNA is synthesized in the 5' to 3' direction. The enzyme that removes tightened coils ahead of the replication fork is topoisomerase . The enzyme that catalyzes new DNA synthesis is DNA polymerase. DNA synthesis occurs continuously on the leading strand. DNA synthesis occurs in small sections on the lagging strand. Fragments of discontinuous DNA synthesis are called Okazaki fragments. Gaps in the sugar-phosphate backbone of DNA are closed by DNA ligase

1

Distinguish between the characteristics associated with each of the four types of gene regulation. 1. Transcriptional 2. Post-transcriptional 3. Translational 4. Post-translational

1. -An activator binds to an enhancer - a repressor binds near a promoter 2. - the correct removal of introns of a pre- mRNA is prevented - Stability of an mRNA is regulated - export of an mRNA to the cytoplasm is blocked 3. - the ability of an mRNA to bind to ribosomes is changed - the 5' end of an mRNA forms a shape that blocks translation 4. - a phosphate group is added to a protein making it inactive - the rate of degradation of a protein is increased

No expression even when lactose is present

1. Promoter is mutated 2. Mutation of CAP

Expression only when lactose is present

1. Wild-type E. coli 2. lacY mutant 3. lacl- mutant with an F' factor carrying lacl+

Expression when lactose is present or absent

1. lacl- mutation 2. operator (laco) is mutated 3. Operator (laco) is mutated, but with an F' factor carrying lacO+ alone

Could Cause Cancer 1.________________ Would likely not cause cancer 2._____________________

1. loss of an essential checkpoint protein 1. loss of the tumor supressor p53 2. the rest

The insertion of a 1.___________ into the promoter of a gene could result in increased expression of the gene, resulting in cancer. A 2._________________ can cause fusion of two genes together, resulting in formation of a chimeric oncogene. A change in the number of 3.___________ of a gene can cause too much protein to be made. A 4._____________ can alter the structure of a protein (but not the total number of amino acids) so that it now has abnormally high activity. Many cells that have accumulated mutations are eliminated by 5._____________________ If a cell accumulates DNA damage during mitosis, the cell cycle can pause at a 6. ______________

1. virus 2. chromosomal translocation 3. copies 4. missense mutation 5. cell death. 6. checkpoint.

Which of the following is a characteristic of double-stranded DNA?

2 nanometers in width, 10 base pairs per turn and 0.34 nanometers per base pair.

Arrange the following in the proper sequence in which they occur during RNA splicing. 1. Lariat is formed 2. U2 binds to branch site 3. 3' splice site is cut

2, 1, 3

Arrange the following proteins in the proper order in which they participate in DNA replication. 1 = Primase 2 = Helicase 3 = Single-strand binding proteins 4 = DNA polymerase I

2, 3, 1, 4.

The carboxyl terminus of a polypeptide will contain amino acids whose codons are closer to the ________ end of the mRNA.

3

DNA polymerases use their ________ activity to remove a mismatched base pair.

3' -> 5' exonuclease.

RNA polymerase and primase both add nucleotides to a

3' OH

There is only one codon, 5'-UGG-3', for the amino acid tryptophan (trp), therefore the anticodon in the tRNA for tryptophan must have the sequence

3'-ACC-5

The complimentary messenger RNA strand that would be synthesized from the DNA base sequence of 5'-CTGAC-3' would be _______.

3'-GACUG-5'

A 5'-CUA-3' codon in an mRNA could be recognized by which of the following anticodon sequences in a tRNA?

3'-GAU-5'

Part of a gene sequence on the DNA reads 5'-ATGCGC-3'. The mRNA will therefore read

3'-UACGCG-5

The amino terminus of a polypeptide will contain amino acids whose codons are closer to the ___ end of the mRNA

5

DNA Polymerase uses what kind of enzymatic activity in the process of proofreading?

5' -> 3' polymerase activity to replace the excised bases. 3' -> 5' exonuclease activity to remove the mismatched bases.

Study the RNA sequence below and determine where the boundaries of an intron could be. Select the answer that includes the entire intron in red. 5' ...CCGAGGUACGAUUUGAGUCGGCUACAGUAUUGA.... 3'

5' ...CCGAGGUACGAUUUGAGUCGGCUACAGUAUUGA.... 3'

Which of the following do snRNPs bind to?

5' and 3' ends of the intron

The template strand of a gene includes the sequence 3'-AGT-5'. The mRNA will therefore have the sequence __________

5'-UCA-3'

The genetic code consists of ____ codons that specify amino acids, and ____ codons that do not specify amino acids.

61/3

A chromosome has undergone a translocation mutation that has completely deleted its centromere region, preventing association with spindle fibers. What will be the fate of this cell? ?

?

A liver cell in an adult human expresses the telomerase gene. What is the likely consequence? ?

?

Cancer progression can result from mechanisms other than mutation (change in the DNA sequence). Which of the following is not an example of such a mechanism? ?

?

Evaluate the statements below and determine which is the best explanation for why bacteria don't use telomerase. ?

?

How does the cell recognize that lactose needs to be metabolized?

?

How is bacterial DNA replication different from eukaryotic DNA replication? ?

?

How is bacterial DNA replication similar to eukaryotic DNA replication? ?

?

If lacI were mutated such that could no longer bind DNA, what effect would this have on the regulation of the operon?

?

If lacO were mutated, what effect would this have on lactose metabolism?

?

In both the lac and trp operons of E. coli, a repressor binds to an operator to block transcription. Identify the most accurate description of these operons.

?

Mutations in the gene that codes for the protein p53 have been implicated in many types of cancer. The p53 protein has a diverse regulatory role, including stopping the cell cycle at G1/S checkpoint when there is damaged DNA, inducing NER mechanisms, and initiating apoptosis. Which of the following mechanisms might result in reduced levels of functional p53 in the cell? ?

?

Place the following events of transcription in the correct order.

?

The cell cycle is regulated by checkpoints during the _______ phases. ?

?

The copying of the information in DNA is efficient because ?

?

The following sequence of DNA is part of the normal, wild-type gene. 5' ATG CGG GTA GTT AGC CGA TAG 3' A deletion occurs during DNA replication, causing the guanine shown in red to be removed from the nucleotide strand. What effect is this most likely to have on the final protein? ?

?

The lac repressor

?

UV light damages DNA by causing ?

?

What is unusual about the initiator tRNA in prokaryotes?

?

What statement about the major and minor grooves is TRUE? ?

?

When a tautomeric shift occurs, which of the following is TRUE? ?

?

Which of the following DNA molecules is the most stable? ?

?

Which of the following DNA sequences is complementary to 5' TAGAC 3'? ?

?

Which of the following mutagens might increase the incidence of slipped-strand mispairing? ?

?

Which of the following mutations might result in the formation of an oncogene? ?

?

Which of the following statements about oncogenes is FALSE? ?

?

Which type of RNA is involved in protein synthesis?

?

New amino acids (other than the initial f-Met) enter at which site?

A

Translation is terminated when a stop codon is presented at the ________ site.

A

According to Chargaff's rule, which of the following statements about double-stranded DNA is TRUE?

A = T and C = G and A + G = C + T.

How could an activator influence gene expression at a promoter far away from the place that it binds DNA?

A Mediator protein is stimulated by the bound activator, and then the Mediator stimulates transcription.

Which of the following mutations might result in the formation of an oncogene?

A cell has a damaged segment of DNA, however p53 proteins are mutated so that they cannot bind to the DNA and activate transcription factors that would stop the cell cycle.

Which of the following could not result from mutations?

A fish in a stream dies from a poison that blocks cellular respiration

Which mutation would allow the cell to pass the G1 checkpoint when it should not?

A mutation in Rb, preventing it from associating with E2F.

What result is characteristic of slipped-strand mispairing mutation?

A protein that, starting at the point of the deletion, has incorrect amino acids and is of abnormal length.

If a protein in the coactivator complex does not function properly, what would be a consequence?

Activators and repressors will not be able to properly effect the rate of transcription

What is NOT a mechanism used by enhancers and repressors to affect gene expression?

All of these are mechanisms used by enhancers or repressors to affect gene expression.

Which of the following is an example of a mutation?

An A-T base pair in a gene is changed to a G-C base pair

How does a cell know which sequences to remove from the pre-mRNA transcript as introns?

Complementary sequences in the snRNP bind to the splice sites in the primary transcript.

Why do complementary nucleotides across the double-stranded DNA bond together using hydrogen bonds rather than covalent bonds?

Covalent bonds would be too strong to allow the double helix to easily separate and make templates available for replication and transcription.

D. A molecule found in the nucleus of cell that contains the cell's genome

DNA

In DNA replication, the goal is synthesis of

DNA

Which of the following best describes transcription?

DNA -> RNA

How do DNA polymerase I and DNA Polymerase III differ?

DNA Polymerase III synthesizes the majority of the DNA, while DNA Polymerase I synthesizes DNA in the regions where the RNA primers were laid down on the lagging strand.

What characteristic of DNA makes nucleotide excision repair (NER) mechanisms possible?

DNA is a double helix so once a damaged region is recognized, it can be removed and synthesized based on the undamaged opposite strand.

What enzyme is responsible for repairing thymine dimers using the energy of light?

DNA photolyase

RNA primers are removed by the action of the enzyme

DNA pol I.

During transcription, only one strand of the DNA will function as a template.

DNA polymerase

Which of the following synthesizes the new DNA strand?

DNA polymerase

Eukaryotic cells store their DNA in the form of linear chromosomes. This creates problems for replication of DNA at the ends of the chromosomes because

DNA polymerase can only synthesize DNA in the 5' to 3' direction.

During, _____________ both strands of the DNA will function as a template.

DNA replication

If DNA ligase was nonfunctional, what would be a likely consequence?

DNA replication would occur, but the lagging strand would be composed of many small fragments.

Why is the lagging strand synthesized in a discontinuous fashion?

DNA synthesis must occur in a 5' to 3' direction, which imposes spatial constraints on the synthesis of the lagging strand.

TFIID binds to

DNA, activators, and RNA Polymerase II.

Which of the following statements about enhancers is TRUE?

Enhancers are sequences to which activators bind.

Select the BEST description of the complexity of eukaryotic gene expression as compared to prokaryotic gene expression.

Eukaryotic transcription is usually influenced by many transcription factors while prokaryotic transcription is usually influenced by only a few transcription factors.

Which of the following statements about repair of thymine dimers is TRUE?

Excision repair can be used to repair thymine dimers as well as other types of damaged DNA.

Which of the following statements regarding the repair of thymine dimers is TRUE?

Excision repair of thymine dimers is possible because there are two strands of DNA.

c. keep a gene product available under all conditions.

False

f. synthesize mRNA for every gene in the genome at all times.

False

A cell that is in an environmentally that has an abnormally low pH will NOT pass which checkpoint?

G1

DNA repair enzymes will be highly active during what phase of the cell cycle?

G2

The success of DNA replication is assessed during the ______ phase.

G2

Cancer results from cells that divide when they should not. A hallmark of cancer is high levels of DNA methylation in cell genomes. Methylation of which genes is MOST likely to lead to cancerous cell formation?

Genes that prevent cell division

Why does the concentration of glucose have an effect on the transcription of the lac operon?

Glucose is the preferred sugar for the bacteria. If it is present, lactose metabolism is suppressed.

RNA polymerase is able to open the DNA double helix as it moves down the template. What type of enzymatic activity does this mean RNA polymerase must possess?

Helicase activity

Which of the following statements is NOT true of the regulation of ferritin production?

IRP aids in ribosomal binding to ferritin mRNA.

What is a major disadvantage to a bacterial cell of having an operon?

If there is a mutation in a regulatory region, none of the proteins will be synthesized.

Introns are generally considered 'free to mutate,' meaning that if a mutation occurs within the intron, it will not effect the functional protein. What is an exception to this axiom?

If there is a mutation in the 3' or 5' splice site, the snurp won't recognize it, and it will not be removed from the mRNA.

What is a difference between DNA replication and RNA transcription?

In DNA replication the helix is never closed after it is opened by helicase, but once RNA polymerase has finished transcribing a region, the double helix closes.

Which of the following is not a mechanism by which viruses could cause cancer?

Infection by a virus could cause the immune system to kill the infected cells by apoptosis.

Evaluate the statements below and determine which is the BEST reason that bacterial cells use operons and polycistronic RNA.

Initiation of transcription of all genes in a biochemical pathway is regulated simultaneously.

Which of the following does not occur during translation in eukaryotes?

Introns are removed by the ribosome.

How is it possible for a single gene to encode more than one polypeptide?

Introns can be removed from pre-mRNA in different combinations.

Which of the following best describes the function of telomerase at the telomere?

It adds new DNA to the longer strand of the telomere overhang.

What would probably NOT increase the accessibility of the DNA for gene transcription?

Methylation of DNA

Which of the following statements about chromatin is TRUE?

Modifying the accessibility of chromatin leads to complex regulation of eukaryotic gene expression.

Sequence the following steps in the development of cancer in an individual with xeroderma pigmentosum (XP). Exposure to UV light Mutation in DNA repair enzyme gene Malignant growth Mutation of a tumor suppressor gene Benigin growth Metastasis

Mutation in DNA repair enzyme gene Exposure to UV light Mutation of a tumor suppressor gene Benigin growth Malignant growth Metastasis

You are examining a gene that normally has the sequence ACGATTTGGCGC But in the mutant fruit fly you have produced, you see the sequence ATGATTTGGTGT What likely caused this mutation?

Mutations induced by HNO2

What mutation would allow the cell to divide when it should not and could possibly lead to cancer?

None of these will lead to cell proliferation.

Which of the following is required to replicate the lagging strand of DNA?

Okazaki fragments, primase and DNA ligase.

The initiating transfer RNA, carrying formylmethionine, binds to which site?

P site

CCR5 is a cell surface receptor protein of white blood cells that attracts them to specific tissue and organs to elicit an immune response. It is also the receptor to which R5 strains of HIV bind to and enter T cells. Between 5-14% of people from Northern European descent possess an allele known as CCR5-Δ32. In this allele, a 32 base pair section of the gene has been deleted. What phenotype would you predict for people carrying the CCR5-Δ32 allele?

People with CCR5-Δ32 will likely have impaired immune function, but will have resistance to HIV infection.

Which of the following statements about the repair mechanism involving photlyase is TRUE?

Photolyase is oxidized and the damaged DNA is reduced.

Why do eukaryotes require a 5' cap and a poly-A tail but prokaryotes don't?

Prokaryotes don't need to transport their RNA out of the nucleus, so they don't need these features.

E. A molecule made of amino acids that correspond to the genetic information in a structural gene.

RNA

In transcription, the goal is synthesis of

RNA

Of which type of molecules are spliceosomes composed?

RNA and protein

During the process of transcription in a eukaryote

RNA polymerase synthesizes new nucleotide chains in the 5' to 3' direction.

The enzyme that accomplishes transcription is termed

RNA polymerase.

Before DNA polymerase can begin assembling DNA nucleotides to produce either the Okazaki fragments of the lagging strand or the continuous molecule of the leading strand, which of the following must occur?

RNA primase constructs a short RNA primer.

The enzyme that travels along a template strand, assembling nucleotides on a growing DNA strand is

RNA primase.

Why is RNA synthesis called 'transcription' and protein synthesis called 'translation?'

RNA synthesis makes a complementary copy of the DNA using nucleic acid and protein synthesis requires the information in the RNA to be changed into a different type of molecule.

What is the MOST important reason a cell exhibits tight transcriptional control over the regulation of gene expression?

Regulation at the transcriptional level is energetically efficient for the cell.

RNA processing does NOT involve which of the following?

Removal of exons

Suppose that a large double-stranded RNA (dsRNA) that corresponds to an enzyme's mRNA sequence was injected into a eukaryotic cell. This dsRNA is cleaved by Dicer into smaller pieces. Normally, the enzyme encoded by the mRNA is being made continuously. What would likely happen to the enzyme's activity?

Some of the smaller pieces could act as siRNAs and cause the endogenous enzyme's mRNA to be degraded, resulting in loss of the enzyme.

Assembly of basal transcription factors begins at the ________ sequence in the promoter.

TATA

The lactose (lac) operon of E. coli is under both positive and negative control. How is the lac operon affected by positive control?

The CAP protein binds near the promoter in the presence of cAMP.

A mutation in which regions of DNA could result in over-expression of ferritin?

The IRP gene or the IRE region of the ferritin gene

How is the lac operon affected by negative control?

The Lac Repressor binds to the operator in the absence of lactose.

The following sequence of DNA is the normal, wild-type gene. 5' ATG CGG GTA GTT AGC CGA TAG 3' An insertion occurs during DNA replication, causing an additional GUANINE to be inserted into the nucleotide strand after the GUANINE shown in red. What effect will this have on the final protein?

The addition of the G will cause a frame shift, resulting in a premature stop codon and a truncated protein.

Which of the following best describes translation?

The amino acid sequence of a protein determines its shape and specific function.

A cell has a mutation such that UvrA is permanently attached to UvrB. What effect might this have on nucleotide excision repair (NER)?

The cell would be able to recognize damaged regions of the double helix, but it would be unable cut the DNA in the appropriate region in preparation for removing the damaged sequence.

Which of the statements is the best explanation for why eukaryotes use so many regulatory elements, such as activators, repressors, coactivators, and basal transcription factors?

The complexity allows specific control over the timing and quantity of the protein produced.

A mutation has occurred that prevents UvrA and UvrB from forming a complex. What result will this have on damaged DNA?

The damaged DNA will not be recognized.

A mutation has occurred that has made UvrD non-functional. What result will this have on damaged DNA?

The damaged segment of DNA will be recognized and cut, but it will not be separated from the healthy strand.

The trp operon of E. coli controls expression of five enzymes that are involved in the biosynthesis of the amino acid tryptophan. A trp repressor protein (trpR) binds to the trp operator to prevent transcription when tryptophan is present. When would the tryptophan synthesis enzymes be made if the trpR gene was mutated?

The enzymes would be made in the presence or absence of tryptophan.

It is often desirable to express eukaryotic genes in bacteria, which can make a protein of interest quickly and cheaply. What is TRUE about this kind of genetic transformation?

The expressed gene must be incorporated into the bacterial chromosome, but its promoter region should be replaced with a bacterial promoter.

If there is an error during the transcription of a gene, what will be the consequence?

The final protein might not be functional.

What stimulates the ribosome to move down one codon?

The formation of a bond between the peptide in the P site and the amino acid in the A site.

Which of the following statements best describes the consequence of this mutation on expression of a transcriptional target gene?

The gene will be expressed, but in less than optimal quantities.

A mutation occurred in the third codon position of a gene, but the protein still functions normally. How is this possible?

The genetic code is redundant, so that mutations in the third position of the codon often result in the same amino acid being specified.

Evaluate the following statements and determine which is the most likely explanation for how the methylation of a guanine might induce mutations in the DNA?

The guanine will not properly hydrogen bond with cytosine across the double helix.

How do you know that the gene being transcribed in the animation is in a prokaryote?

The initiation of transcription involves a sigma factor.

Genes that encode proteins are first transcribed to mRNA, and then are translated into protein. What is the MOST important factor determining the control of gene expression?

The level of transcription (when a gene is transcribed to mRNA)

Cancer cells often are missing chromosomes. How could loss of chromosomes result in cancer?

The missing chromosomes could have contained tumor-suppressor genes.

If an organism had a DNA polymerase III that lost its ability to proofread, which of the following statements would be TRUE?

The mutation rate for the organism would increase, and more substitutions would be seen in its DNA than in an organism that had functional proofreading.

A pregnant mother recently had an ultrasound that indicated massive defects in the formation of her unborn baby's heart. Other oddities were noted in the spinal cord region, the kidneys, and the formation of the facial features. She had an amniocentesis to examine the baby's karyotype, and it was noted that there was a deletion of a small piece of one chromosome. The doctors advised her that her that she would likely miscarry. The devastated parents consult you as a genetic advisor on the likelihood that a future pregnancy would end similarly. What advice do you give this couple?

The mutation was probably a germ-line mutation that only affected a single egg or sperm, so they should try to have more children.

If there is an error during translation of a gene, what will be the consequence?

The protein might not be functional.

Select the statement that best explains why the replication machinery is found at the replication fork.

The replication machinery must be able to open and stabilize the template DNA, and it must have access to both template strands for replication.

RNA Polymerase II by itself does not have a strong affinity for binding DNA. Select the explanation that describes why cells do not need for RNA polymerase II to have a strong affinity for binding DNA for transcription to occur.

The requirement of general transcription factors to bind RNA polymerase II to the DNA molecule gives the cell more precise control over transcription.

How does a bacterial ribosome initially bind to the mRNA?

The small subunit binds to ribosomal binding sequence

How does a eukaryotic ribosome initially bind to the mRNA?

The small subunit binds to the 5' guanine cap

If an aminoacyl-tRNA synthetase added the wrong amino acid to a tRNA, what would happen?

The tRNA would carry the worng amino acid, and it would be incorporated into the growing protein.

If an aminoacyl-tRNA synthetase added the wrong amino acid to a tRNA, what would happen?

The tRNA would carry the wrong amino acid, and it would be incorporated into the growing protein.

Why are nucleotide triphosphates used to polymerize RNA?

The triphosphate is a high energy molecule so that polymerization is spontaneous.

Many genes that are associated with cancer can become mutated due to slipped-strand mispairing. These genes include p53, retinoblastoma, Wilms tumor, and the breast cancer gene BRCA1. What characteristic would you expect to find in all these genes?

They all have repetitive sequences in the gene.

How could drug developers use RNA interference in a medical application?

They could stop the production of a defective protein.

Evaluate the statements below and determine which is the best reason for why eukaryotes use basal transcription factors?

They give the cell tight control over transcription

What changes would a scientist want to make to a eukaryotic gene before they insert it into a bacterial chromosome to be expressed?

They should remove the introns.

B. The synthesis of an RNA copy of a gene.

Transcription

Which of the following statements about structural gene is TRUE?

Transcription of structural genes requires DNA sequences that are not part of the gene itself

C. The synthesis of a specific sequence of amino acids on a ribosome.

Translation

a. make additional cells of the same type in response to a demand.

True

b. synthesize enzymes to metabolize a particular nutrient.

True

d. execute a specific program of development (e.g. to become a blood cell or immune cell).

True

e. stop synthesis of a cellular component when there is enough available in the cell.

True

How does ultraviolet light result in the formation of thymine dimers?

Ultraviolet light provides the energy for covalent bond formation between two thymines.

Which protein cuts the damaged DNA strand?

UvrC

Which protein has a helicase function?

UvrD

An actively dividing cell is missing an entire chromosome. How might this lead to cancer?

Various tumor suppressor genes may have been deleted from the genome, so cell proliferation occurs regardless of the damaged genome.

At what point in gene expression do molecules go from being information storage molecules to metabolic and structurally functional molecules?

When RNA is translated into protein.

How does glucose effect the lac operon?

When glucose levels are low, it stimulates the production of cAMP, which binds to and activates the CAP protein, allowing it to bind to the DNA.

Which of the following is NOT a mechanism that cells use to ensure their DNA is accurately replicated?

When mismatched nucleotides are detected, DNA polymerase will begin to synthesize DNA in the 3' to 5' direction to correct the mistake.

Shortly after RNA polymerase begins to transcribe a pre-mRNA, _______________ is added.

a 5' cap

Which of the following statements about eukaryotic mRNA is TRUE?

a cap is added to their 5' end, a poly-A tail is added to their 3' end, and each usually specifies only a single protein

Slipped-strand mispairing may cause deletions resulting in

a frameshift mutation.

The genetic code is degenerate. That means

a particular amino acid can be specified by more than one codon.

Which of the following does not occur during the processing of eukaryotic mRNA?

a ribosome recognition sequence is added.

DNA replication in bacteria begins at

a single origin and proceeds in both directions.

A protein that binds to DNA and activates transcription of some genes is a/an

activator

Function of __________ can be modulated by binding of small effector molecules, protein-protein interactions, or covalent modifications.

activators and repressors

In the absence of lactose, the lac repressor is

active and can bind to the operator.

After a tautomeric shift in adenine

adenine bonds with cytosine.

There is only one start codon, AUG. This means that

all newly-made polypeptides have a methionine at their amino end.

Which of the following statements about RNA splicing is FALSE?

all of these choices are true

The lac repressor is inactivated by binding to which of the following?

allolactose

Telomerase is unique because it contains

an RNA molecule.

A regulatory element that can function from a large distance (e.g. tens of thousands of base pairs) from a promoter is called

an enhancer.

Small effector molecules

are often end products or key metabolites of a metabolic pathway.

Small RNA gene regulation

bind to an mRNA, resulting in destruction of the mRNA or blockage of translation.

Small RNAs, typically 22 nucleotides long, that function in post-transcriptional regulation of gene activity are produced

by digestion of double-stranded RNA into smaller pieces.

When in a complex with ________, the CAP protein binds to the CAP site and ________ the expression of the lac operon.

cAMP ; switches on

A carcinogen is a chemical or treatment that

causes mutations that can affect gene activity.

A nucleotide deletion in DNA replication

causes the amino acids inserted after the deletion to be incorrect.

A mutation that causes a change in a single nucleotide in DNA

changes the corresponding nucleotide in mRNA, resulting in a different codon.

The idea that gene regulation involves multiple factors is called

combinatorial contro

A eukaryotic cell that receives a "go-ahead" signal at the G1 checkpoint of the cell cycle will

complete the cycle and divide.

How does UV light and other ionizing radiation damage DNA molecules?

creating thymine dimers between adjacent thymines in the DNA chain.

The proteins ________ work together to free the transcription factor that is bound by the retinoblastoma protein.

cyclin and cyclin dependent kinase

The protein ________ acts as an endonuclease in the first step of RNA interference.

dicer

Mutated forms of the Rb protein

do not bind to E2F thereby promoting uncontrolled cell division.

The genetic material in bacteria is

double-stranded DNA.

RNA interference is stimulated in the presence of ________ in the cell.

double-stranded RNA

In the nucleus, both 5' and 3' modifications to mRNA are important for

export of the mRNA to the cytosol

DNA pol III can initiate DNA synthesis.

false

The terminator of a gene is located upstream of the coding region.

false

The three base sequence on the transfer RNA is the codon.

false

The trp operon consists of ________ genes that encode tryptophan biosynthesis enzymes.

five

The pairing of nitrogenous bases in DNA is specific because

functional groups on each of the bases form hydrogen bonds with functional groups on only one other base.

The lac operon is expressed when

glucose is low and lactose is present.

The enzyme that unwinds a segment of the DNA molecule is...

helicase.

The proofreading function of DNA polymerase reduces the error rate from about one in a million base pairs to about one in a ________ base pairs.

hundred million.

In a tautomeric shift

hydrogen atoms move to form a nucleotide base with altered bonding properties.

What kind of bond do thymine dimers weaken?

hydrogen bonds.

A difference between bacterial and eukaryotic transcription

in eukaryotes, there are different RNA polymerases (I, II, and III).

Slipped-strand mispairing requires that a DNA sequence be present

in multiple copies on both homologous chromosomes.

Where does the greatest variability among codons specifying the same amino acid occur?

in the third nucleotide of the triplet

In the absence of tryptophan, the trp repressor is

inactive and cannot bind to the operator.

When a transcription factor interacts with DNA,

it forms noncovalent bonds with functional groups on the nitrogenous bases.

The lac repressor binds to what site within the lac operon?

lacO

Which region associated with the lac operon is not involved in the binding of RNA polymerase?

lacZ

Which of the following is not part of the lac operon?

lacl

Operon activity when glucose is present

low; CAP does not bind to the activator binding site, and transcription ofthe operon is turned off.

A. The molecule that carries information from the DNA specifying a polypeptide to ribosomes

mRNA

During the process of translation in a eukaryote

mRNA interacts with ribosomes in the cytoplasm.

A tRNA with anticodon 3'-UAC-5' would be attached to the amino acid

methionine (met

Modification of bases in DNA, usually resulting in inhibition of transcription, results from

methylation

A difference between bacterial and eukaryotic translation is

modifications to the 5' end of mRNA help it to bind to ribosomes only in eukaryotes

Contains information to be translated (as codons)

mrna, gene

During the replication of a DNA molecule

new base pairs must be formed according to Chargaff's rule.

The nucleic acid sequence in mRNA is determined by

nucleotide sequence in DNA.

The protein ________ checks for damaged DNA, thereby acting as a "quality control" for the cell.

p53

During slipped-strand mispairing, homologous chromosomes

pair up with each other, but out of register.

At which of the following level(s) can gene expression be regulated in eukaryotes?

passage of mRNA through the nuclear membrane, destruction of the mRNA, and rate of protein synthesis

The amino acids carried by the transfer RNA are joined by

peptide bonds.

The correct structure of DNA monomers can be presented as

phosphate-sugar-base.

A mature mRNA will ha _________ ve aadded.

poly A tail

Combinatorial control of gene expression does not involve

polycistronic RNA.

RNA intereference is a mechanism for silencing gene expression at the

post-transcriptional but pre-translational level.

A tumor suppressor gene normally functions to

prevent development of cancer.

A tRNA with anticodon 3'-GGG'-5' would be attached to the amino acid

proline (pro)

RNA polymerase binds to the

promoter

The transcription enzyme first attaches to the ________ of the gene.

promoter

The segment of the DNA molecule where messenger RNA synthesis begins is called the...

promoter region.

Translation is the synthesis of

proteins from mRNA.

The Ras protein normally regulates cell growth. A mutation that occurs in the gene encoding Ras can cause Ras to become overactive, which results in cancer. This means that Ras is an example of a/an

proto-oncogene.

A protein that binds to DNA and blocks activation of a small number of genes is a/an

repressor

What protein would not interact with a coactivator?

repressors

Forms part of the enzyme that drives translation

ribosomal rna, ribosomal protein

DNA replication is said to be

semiconservative.

Proofreading by DNA polymerase involves the removal of

several bases on the newly synthesized strand of DNA.

The snRNPs are also called

snurps.

The reason that the genetic code can correctly specify the order of amino acids in a polypeptide is

specific tRNAs become attached to specific amino acids.

The mutations observed by the Lederbergs were

spontaneous.

In the cytosol, the poly A tail is important for of the mRNA.

stability

When a tautomeric shift occurs, the resulting nulceotide is a(n) __________ of the nucleotide prior to the shift.

structural isomer

DNA polymerases cannot replicate

the 3' end of linear chromosomes.

In light repair

the covalent bonds between the thymine dimers are broken.

In eukaryotes, transcription to produce an mRNA must occur in

the nucleus, where the chromosomal DNA is found.

If a frameshift mutation causes a stop codon to be inserted into the DNA sequence,

the resulting protein will be too short and non-functional.

Which of the following occurs as the ribosome shifts down the mRNA by a distance of three nucleotides?

the tRNA that was in the P site moves into the E site

A characteristic shared by eukaryotic mRNA, tRNA, and ribosomal RNA is that...

they are all transcribed from DNA

Which of the following statement(s) about basal transcription factors is(are) TRUE?

they are essential for transcription and they cannot increase the rate of transcription by themselves

Which of the following statements about basal transcription factors is TRUE?

they are essential for transcription and they cannot increase the rate of transcription by themselves

During _______________, only one strand of the DNA will function as a template.

transcription

The most efficient control of eukaryotic gene expression is achieved at the level of

transcription initiation.

When both glucose and lactose are present,

transcription is turned off.

The structure that causes the synthesis of RNA to cease is known as the

transcription terminator

At the E site

transfer RNA is released

In the cytosol, the 5' cap is recognized by proteins that enable the mRNA to be

translated

Which of these events occur as a prokaryotic mRNA is being transcribed?

translation of protein

What level of regulation do eukaryotes possess that prokaryotes do not?

transport of RNA out of the nucleus

Structural RNA that links an amino acid to an anticodon

trna

In the presence of tryptophan, tryptophan binds to the

trp repressor.

Eukaryotic transcription factors include activators and coactivators.

true

If DNA polymerase III could add nucleotides in either direction, Okazaki fragments would no longer form.

true

A gene encodes a protein that normally functions in promoting the programmed cell death of blood cells that have accumulated damage to DNA. A mutation in this gene can result in leukemia (cancer of the blood). This gene is an example of a/an

tumor-suppressor gene.

Splicing joins together

two exons.

The assembly of transcription factors begins

upstream from the transcription start site.

Oncogenes and tumor-suppressor genes have the shared property that

when either type of gene is mutated, cancer can result.

What is the MOST important reason a cell would have translational control over the regulation of gene expression?

At the translational level, protein synthesis can be turned on and off quickly to respond to the needs of the cell.

A large region of a promoter has been deleted upstream of a gene. What effect will this have on transcription of the gene?

Basal transcription factors won't bind to the template DNA, therefore RNA polymerase will not bind to the template DNA and transcription will not occur.

Which of the following statements about tRNA molecules is TRUE?

Bases in the tRNA loops do not pair with any other bases

Why is breast cancer a very deadly form of cancer?

Because breasts contain numerous blood vessels and lymph nodes, so breast cancer can easily metastasize and spread throughout the body.

DNA polymerase occasionally makes errors and adds an incorrect base. A new strand of DNA is being produced, and the template strand contains a G. Based on your knowledge of the structure of DNA, why is it more likely that DNA polymerase would accidently add a T to the new strand instead of a G or an A.?

Because the structure of T and C are similar as they both have a single ring.

Which of the following is not a reason why cells need to be able to repair damaged DNA?

Cells need to change base pairs to be able to express different types of proteins