Bio unit 6

Which of the following messenger RNA sequences could code for both of the two amino acid sequences above, simply by a shift in the reading frame?

. . . AGCAGCAGCAGC . . .

Which of the following DNA strands will code for the amino acid sequence shown above?

. . . CCTTCGCCT . . .

The mRNA transcribed from the DNA would read

5' AUC AAG UUU GGC GCA UUG UAA 3'

Which of the following statements concerning a gene is correct? A A gene can code for a specific protein. B A gene can exist in alternate forms called introns. C A gene undergoes crossing-over during DNA replication. D A gene that is very similar in sequence in a human and in a bacterium is probably a recent mutation. E A gene that is expressed in every offspring of every generation is recessive.

A gene can code for a specific protein.

Operon Transcription Which is a scientific claim that is consistent with the information provided and Figure 1 ? A The presence of excess lactose blocks the functioning of RNARNA polymerase in this operon. B When bound to the operator, the repressor protein prevents lactose metabolism in E. coli. C The binding of the repressor protein to the operator enables E. coli to metabolize lactose. D Allolactose acts as an inducer that binds to the operator, allowing E. coli to metabolize lactose.

B When bound to the operator, the repressor protein prevents lactose metabolism in E. coli.

Cells that contain only circular chromosomes are most probably which of the following? A Protist cells B Fungal cells C Bacterial cells D Plant cells

Bacterial Cells

Which of the following best explains a process occurring between point 1 and point 2 in Figure 3 ? A α-MSHα-MSH is produced. B The TYRTYR gene is transcribed. C Polypeptides are removed from a protein. D A poly‑A tail is added to RNARNA.

D A poly‑A tail is added to RNARNA.

Which of the following statements best explains the role of Enzyme 1 in the DNA replication process? A Enzyme 1 is a DNADNA ligase that joins together the DNADNA fragments at a replication fork to form continuous strands. B Enzyme 1 is a DNADNA primase that catalyzes the synthesis of RNARNA primers on the lagging strand of a replication fork. C Enzyme 1 is a DNADNA polymerase that synthesizes new DNADNA by using the leading and lagging strands of a replication fork as templates. D Enzyme 1 is a topoisomerase that relieves tension in the overwound DNADNA in front of a replication fork.

D Enzyme 1 is a topoisomerase that relieves tension in the overwound DNADNA in front of a replication fork.

Which of the following best describes an event during step 2 in the simplified model above? A A new RNA molecule is synthesized using a DNA template. B A new polypeptide is synthesized using an RNA template. C Thymine nucleotides in an RNA molecule are replaced with uracil nucleotides. D Noncoding sequences are removed from a newly synthesized RNA molecule.

D Noncoding sequences are removed from a newly synthesized RNA molecule.

Which of the following best predicts the phenotype of an individual who is homozygous for this TYR mutation? A The mutation will cause a single amino acid change in the TYRTYR protein, which will not be enough to disrupt its function. Therefore, those with this mutation will produce melanin in the hair, skin, and eyes and tan in response to UVUV radiation. B The mutation will cause a single amino acid change in the TYRTYR protein, leading to a nonfunctional TYRTYR protein. Therefore, those with this mutation will lack melanin in the hair, skin, and eyes and will not tan in response to UVUV radiation. C The mutation will change all subsequent amino acids in the TYRTYR protein, leading to nonfunctional TYRTYR protein. Since the TRP1TRP1 and TRP2TRP2 genes were not affected, the TRP1TRP1 and TRP2TRP2 proteins will fill the role of the TYRTYR protein. Therefore, those with this mutation will produce melanin in the hair, skin, and eyes in response to UVUV radiation. D The mutation will change all subsequent amino acids in the TYRTYR protein, leading to nonfunctional TYRTYR protein. Individuals with this mutation will lack melanin in their hair, skin, and eyes and will not tan in response to UVUV radiation.

D The mutation will change all subsequent amino acids in the TYRTYR protein, leading to nonfunctional TYRTYR protein. Individuals with this mutation will lack melanin in their hair, skin, and eyes and will not tan in response to UVUV radiation.

Which of the following evidence best supports a claim that tryptophan functions as a corepressor? A Normal expression of trpRtrpR causes the trptrp operon to be transcribed regardless of tryptophan levels. B When the operator sequence is mutated, the trptrp operon is not transcribed. C The trpRtrpR gene codes for a repressor protein that has a DNADNA binding domain. D When trpRtrpR is mutated, the trptrp operon is transcribed regardless of tryptophan levels.

D When trpRtrpR is mutated, the trptrp operon is transcribed regardless of tryptophan levels.

tRNA molecules deliver amino acids to ribosomes where the amino acid next A forms an ionic bond with another amino acid B is deaminated and catabolized C becomes an anticodon D is covalently bonded to a growing polypeptide E forms hydrogen bonds with esters

D is covalently bonded to a growing polypeptide

Enzyme used during replication to attach Okazaki fragments to each other

DNA ligase

Enzyme used to position nucleotides during DNA replication

DNA polymerase

Which of the following correctly explains where DNA replication will begin on the strand oriented 5'→3', reading from left to right? DNADNA replication will be randomly initiated along the unwound portion of the DNADNA strand since base pairing will occur. B DNADNA replication cannot occur since there is already RNARNA base pairing with the template strand. C DNADNA replication will be initiated immediately to the left of the RNARNA, since DNADNA polymerase requires an RNARNA primer. D DNADNA replication will be initiated at the site of the topoisomerase since that is where DNADNA begins to uncoil.

DNA replication will be initiated immediately to the left of the RNA, since DNA polymerase requires an RNA primer.

Gel Electrophoresis and Transformation Which of the following statements best explains the experimental results observed in Figure 1 ? A E. coli in both lanes BB and CC have been successfully transformed and contain additional genetic information. B E. coli in lane BB have been successfully transformed and contain additional genetic information. C E. coli in lane CC have been successfully transformed and contain additional genetic information. D Which E. coli have been transformed cannot be determined from this gel.

E. coli in lane CC have been successfully transformed and contain additional genetic information.

Semiconservative replication Which of the following best helps explain how the process represented in Figure 1 produces DNA molecules that are hybrids of the original and the newly synthesized strands? A Each template strand is broken down into nucleotides, which are then used to synthesize both strands of a new DNADNA molecule. B Each template strand is broken into multiple fragments, which are randomly assembled into two different DNADNA molecules. C Each newly synthesized strand is associated with another newly synthesized strand to form a new DNADNA molecule. D Each newly synthesized strand remains associated with its template strand to form two copies of the original DNADNA molecule.

Each newly synthesized strand remains associated with its template strand to form two copies of the original DNADNA molecule.

Basic Transcription

Initiation of transcription is occurring because a strand of RNA is being produced from a DNA template strand.

Based on the universal genetic code, which of the following represents the correct polypeptide that will result from translation of the mRNA molecule shown, beginning with the first available start codon?

Met-Val-Thr-Lys-Phe-Gly-His

Base Pairing Rules in DNA

Since the %A%A and the %T%T are approximately the same in each sample, adenine and thymine molecules must pair up in a double-stranded DNA molecule.

Which of the following claims about the TYR, TRP2, and TRP1 mammalian genes is most likely to be accurate? A The TYRTYR, TRP2TRP2, and TRP1TRP1 genes are located next to each other on a single chromosome and are organized into an operon. B The TYRTYR, TRP2TRP2, and TRP1TRP1 genes may be located on different chromosomes but are activated by the same transcription factor. C The TYRTYR, TRP2TRP2, and TRP1TRP1 genes are identical genes since they are activated by the same transcription factor. D The TYRTYR, TRP2TRP2, and TRP1TRP1 genes may be located on different chromosomes but with identical operator sequences.

The TYRTYR, TRP2TRP2, and TRP1TRP1 genes may be located on different chromosomes but are activated by the same transcription factor.

A tobacco plant can be made to express a gene from fireflies, resulting in the emission of light. Which of the following is the basis for this phenomenon? A Chloroplasts can be made to produce light if firefly proteins are injected into plant cells. B Fireflies and tobacco plants share a recent common ancestor. C Fireflies and tobacco plants are infected by the same kinds of bacteria. D Transcription and translation are fundamen-tally similar in both fireflies and tobacco plants. E Most enzymes in fireflies have the same amino acid sequence as the enzymes in tobacco plants.

Transcription and translation are fundamen-tally similar in both fireflies and tobacco plants.

Process in which a protein is assembled at a ribosome

Translation

UV Exposure and DNA Mutations Which of the following statements best explains what is shown in Figure 1 ? A UVUV exposure triggers DNADNA replication, which results in rapid cell proliferation. B Naturally occurring dimers are removed by the UVUV photons, causing misshapen DNADNA, which results in replication errors. C The hydrogen bonds between base pairs absorb the UVUV photons, separating the two DNADNA strands, which results in rapid DNADNA replication. D UVUV photons cause dimers to form, leading to misshapen DNADNA, which results in replication and transcription errors.

UV photons cause dimers to form, leading to misshapen DNA, which results in replication and transcription errors.

Which of the following pieces of evidence would best support the researchers' claim above? A When researchers applied a drug that activates adenylyl cyclase to the mutant mice's ears, the level of melanin increased. B When researchers viewed sections of mutant mouse ears under the microscope, they found melanocyte numbers comparable to nonmutant mice. C When researchers exposed the mutant mice to UVUV radiation, the amount of POMCPOMC mRNAmRNA in keratinocytes did not change. D When researchers exposed the mutant mice to UVUV radiation, the level of melanin production did not change.

When researchers applied a drug that activates adenylyl cyclase to the mutant mice's ears, the level of melanin increased.

If a segment of DNA is 5'-TAC GAT TAG-3', the RNA that results from the transcription of this segment will be A 3'-TAC GAT TAU-5' B 3'-ATG CTA ATA-5' C 3'-UAC GAU UAG-5' D 3'-AAC GAU UAA-5' E 3'-AUG CUA AUC-5'

3'-AUG CUA AUC-5'

Effects of Alternative Splicing A cell needs to metabolize the substrate illustrated in Figure 1 for a vital cellular function. Which of the following best explains the long-term effect on the cell of splicing that yields only enzyme C mRNA? A The cell will die because it is unable to metabolize the substrate without enzyme AA, which is structurally specific for the substrate shown. B The cell will remain healthy because all three of the above enzymes can metabolize the substrate, as they are from the same gene. C The cell will remain healthy because the enzyme CC mRNAmRNA will undergo alternative splicing again until it transformed into enzyme AA mRNAmRNA. D The cell will remain healthy because enzyme-substrate interactions are nonspecific and enzyme CC will eventually metabolize the substrate.

A The cell will die because it is unable to metabolize the substrate without enzyme AA, which is structurally specific for the substrate shown.

Based on the information in Table 1, which of the following best predicts a key difference in prokaryotes and eukaryotes with regard to transcription and translation? A The two processes will occur simultaneously in prokaryotes but not eukaryotes. B Prokaryotic mRNAmRNA is shorter than eukaryotic mRNAmRNA. C Eukaryotic mRNAmRNA contains more coding regions than prokaryotic DNADNA. D The processing of mRNAmRNA by eukaryotes is required for the mRNAmRNA to leave the nucleus.

A The two processes will occur simultaneously in prokaryotes but not eukaryotes.

Analysis of DNA sequences from two individuals of the same species results in a greater estimate of genetic variability than does analysis of amino acid sequences from the same individuals because A different DNA sequences can code for the same amino acid B some amino acid variations cannot be detected by protein electrophoresis C DNA sequencing is a more reliable technique than protein electrophoresis D proteins are more easily damaged than is DNA E DNA is more heat-sensitive and therefore varies more

A different DNA sequences can code for the same amino acid

A woman develops Huntington's disease. Her father had the disorder. Her mother did not, and there is no history of the disorder in the mother's family. Which of the following best explains how the woman inherited Huntington's disease? A She inherited an allele with fewer than 40 CAGCAG repeats in the HTTHTT gene because her mother did not have Huntington's disease. B She inherited an allele with more than 40 CAGCAG repeats in the HTTHTT gene from her father. C Her mother produced eggs that all have more than 40 repeats in the HTTHTT gene. D Her mother produced eggs that all have fewer than 40 CAGCAG repeats in the HTTHTT gene.

B She inherited an allele with more than 40 CAGCAG repeats in the HTTHTT gene from her father.

Which of the following is the most likely consequence of a mutation at the operator locus that prevents binding of the repressor protein? A Expression of the structural genes will be repressed, even in the presence of lactose. B Beta-galactosidase will be produced, even in the absence of lactose. C RNA polymerase will attach at the Plac locus, but transcription will be blocked. D The operator locus will code for a different protein and thereby prevent transcription of the structural gene.

Beta-galactosidase will be produced, even in the absence of lactose.

Based on the information in Figure 1, which type of mutation explains the nature of the change in DNA that resulted in cystic fibrosis in the affected individual? A Substitution, because the amino acid tryptophan is replaced with glycine. B Insertion, because an extra guanine is present, which changes the reading frame. C Deletion, because a thymine is missing, which changes the reading frame. D Duplication, because the amino acid leucine occurs twice, which changes the reading frame.

C Deletion, because a thymine is missing, which changes the reading frame.

Nucleotide base pairing in DNA is universal across organisms. Each pair (T−A; C−G) consists of a purine and a pyrimidine. Which of the following best explains how the base pairs form? A Ionic bonds join two double-ringed structures in each pair. B Hydrogen bonds join two single-ringed structures in each pair. C Hydrogen bonds join a double-ringed structure to a single-ringed structure in each pair. D Covalent bonds join a double-ringed structure to a single-ringed structure in each pair.

C Hydrogen bonds join a double-ringed structure to a single-ringed structure in each pair.

Which of the following statements provides the best explanation of the processes illustrated in Figure 1 ? A Introns are removed from the pre-rRNArRNA, and the mature rRNArRNA molecules are joined and then translated to produce the protein portion of the ribosome. B Introns are removed from the pre-rRNArRNA, and each mature rRNArRNA molecule is translated to produce the proteins that make up the ribosomal subunits. C Sections of the pre-rRNArRNA are removed, and the mature rRNArRNA molecules are available to combine with proteins to form the ribosomal subunits. D Sections of the pre-rRNArRNA are removed, and the mature rRNArRNA molecules are available to bring different amino acids to the ribosome.

C Sections of the pre-rRNArRNA are removed, and the mature rRNArRNA molecules are available to combine with proteins to form the ribosomal subunits.

Template Strand in Transcription Which of the following best explains what strand X represents? A A complementary RNARNA sequence, because it contains thymine B The coding strand in this process, because it is being read 3′3′ to 5′5′ C The antisense strand, because it is serving as a template D The pre‑mRNAmRNA, because it does not yet have a GTPGTP cap

C The antisense strand, because it is serving as a template

Which of the following claims best explains why keratinocytes do not produce melanin? A Keratinocytes do not contain the TYRTYR, TRP2TRP2, and TRP1TRP1 genes. B Keratinocytes do not contain the MC1RMC1R gene. C Keratinocytes do not express the MITFMITF gene. D Keratinocytes do not express the POMCPOMC gene.

D Keratinocytes do not express the POMCPOMC gene

Which of the following best predicts the most direct effect of exposing prokaryotic cells to streptomycin? A Amino acid synthesis will be inhibited. B No mRNAmRNA will be transcribed from DNADNA. C Posttranslational modifications will be prevented. D Synthesis of polypeptides will be inhibited.

D Synthesis of polypeptides will be inhibited

RNA processing Which of the following best explains the process represented by Figure 1 ? A The synthesis of mRNA in the 5′5′ to 3′3′ direction from DNA B The modification of a protein to produce a functional form of that protein C The translation of an mRNA molecule into a polypeptide D The enzyme-regulated processing of pre‑mRNA into mature mRNA

D The enzyme-regulated processing of pre‑mRNA into mature mRNA

The features of this model provide evidence for which explanation of why all growing strands are synthesized in a 5′ to 3′ direction? A The two strands need to be antiparallel to bond properly. B Thymine and adenine would not bond properly if the strand grew from 3′3′ to 5′5′. C The translation of mRNAmRNA occurs in the 5′5′ to 3′3′ direction; therefore, the growing DNADNA strand must also grow in the 5′5′ to 3′3′ direction. D The phosphate group, attached to the 5′5′ carbon of the dTMPdTMP, forms a covalent bond with the oxygen atom attached to the 3′3′ carbon of the growing strand.

D The phosphate group, attached to the 5′5′ carbon of the dTMP, forms a covalent bond with the oxygen atom attached to the 3′3′ carbon of the growing strand.

Small single-stranded RNA molecules called microRNAs (miRNAs) are capable of base pairing with specific binding sites in the 3′ untranslated region of many mRNA transcripts. Transcription of gene Q yields an mRNA transcript that contains such an miRNA binding site, which can associate with miRNA‑delta, a specific miRNA molecule. Which of the following best supports the claim that binding of miRNA‑delta to the miRNA binding site inhibits translation of gene Q mRNA? A When the promoter for gene Q is altered, transcription is inhibited. B Translation of Q mRNAmRNA is inhibited regardless of whether the miRNAmiRNA binding site sequence is altered. C Translation of Q mRNAmRNA is inhibited in the absence of miRNAmiRNA‑delta. D When the miRNAmiRNA binding site sequence is altered, translation of Q mRNAmRNA occurs in the presence of miRNAmiRNA-delta.

D When the miRNAmiRNA binding site sequence is altered, translation of Q mRNAmRNA occurs in the presence of miRNAmiRNA-delta.

Which of the following scientific claims is most consistent with the information provided in Figure 1 ? A Gene XX codes for a transcription factor required for transcription of gene DD. B A single transcription factor regulates transcription similarly, regardless of the specific gene. C Transcription of genes AA, BB, and CC is necessary to transcribe gene EE. D Different genes may be regulated by the same transcription factor.

Different genes may be regulated by the same transcription factor.

Histone methyltransferases are a class of enzymes that methylate certain amino acid sequences in histone proteins. A research team found that transcription of gene R decreases when histone methyltransferase activity is inhibited. Which scientific claim is most consistent with these findings? A DNADNA methylation inhibits transcription of gene RR. B Histone modifications of genes are usually not reversible. C Histone methylation condenses the chromatin at gene RR so transcription factors cannot bind to DNADNA. D Histone methylation opens up chromatin at gene RR so transcription factors can bind to DNADNA more easily.

Histone methylation opens up chromatin at gene RR so transcription factors can bind to DNADNA more easily.

Which of the following best explains how this model illustrates DNA replication of both strands as a replication fork moves? A II and IVIV are synthesized continuously in the 5′5′ to 3′3′ direction. B IIII and IIIIII are synthesized in segments in the 3'3′ to 5'5′ direction. C II is synthesized continuously in the 5′5′ to 3′3′ direction, and IIIIII is synthesized in segments in the 5′5′ to 3′3′ direction. D IIII is synthesized in segments after DNADNA polymerase is released from synthesizing strand IVIV.

II is synthesized continuously in the 5′5′ to 3′3′ direction, and IIIIII is synthesized in segments in the 5′5′ to 3′3′ direction.

The Trp operon is a coordinately regulated group of genes (trpA-trpE) that are required for tryptophan biosynthesis in E. coli. Based on the figure above, which of the following correctly describes the regulation of the Trp operon? A In the absence of tryptophan, the repressor is active and binds to the Trp operator, preventing RNA polymerase from transcribing the operon. B In the presence of tryptophan, the repressor is active and binds to the Trp operator, preventing RNA polymerase from transcribing the operon. C In the absence of tryptophan, the trpR gene is inactive, preventing the production of the repressor that blocks expression of the operon. D In the presence of tryptophan, the trpR gene is inactive, preventing the production of the repressor that blocks expression of the operon.

In the presence of tryptophan, the repressor is active and binds to the Trp operator, preventing RNA polymerase from transcribing the operon.

Both liver cells and lens cells have the genes for making the proteins albumin and crystalline. However, only liver cells express the blood protein albumin and only lens cells express crystalline, the main protein in the lens of the eye. Both of these genes have enhancer sequences associated with them. The claim that gene regulation results in differential gene expression and influences cellular products (albumin or crystalline) is best supported by evidence in which of the following statements? A Liver cells possess transcriptional activators that are different from those of lens cells. B Liver cells and lens cells use different RNARNA polymerase enzymes to transcribe DNADNA. C Liver cells and lens cells possess the same transcriptional activators. D Liver cells and lens cells possess different general transcription factors.

Liver cells possess transcriptional activators that are different from those of lens cells.

Diagram of 5 to 3 DNA Synthesis Which of the following best explains what process is represented in Figure 1 ? A New DNADNA strands are being synthesized in the 3'3′ to 5'5′ direction from their DNADNA templates. B New DNADNA strands are being synthesized in the 5'5′ to 3'3′ direction from their DNADNA templates. C A new RNARNA strand is being synthesized in the 3'3′ to 5'5′ end from its DNADNA template. D Two new RNARNA strands are being synthesized in both directions from their DNADNA templates. Answer B

New DNA strands are being synthesized in the 5'5′ to 3'3′ direction from their DNA templates.

Which of the following statements best explains how protein X regulates gene expression? A Protein X is responsible for processing pre-mRNA. B Protein X is responsible for activating transcription of some genes but not others. C Protein X is a member of some cytoplasmic protein complexes but not others. D Protein X causes specific base-pair changes to produce new alleles.

Protein X is responsible for activating transcription of some genes but not others.

Enzyme used in the synthesis of mRNA

RNA polymerase

Based on the information provided in Figure 1 and Figure 2, which of the following best predicts the effects of a mutation in the promoter of the TYR gene that prevents it from being transcribed? A DNADNA damage due to UVUV radiation will be strongly inhibited, resulting in a positive selection pressure. B DNADNA damage due to UVUV radiation will be strongly inhibited, resulting in a negative selection pressure. C Skin pigmentation will not be able to change, resulting in a positive selection pressure. D Skin pigmentation will not be able to change, resulting in a negative selection pressure.

Skin pigmentation will not be able to change, resulting in a negative selection pressure.

Which claim is most consistent with the information provided by the diagram and current scientific understanding of gene regulation and expression? A Reversible changes in the DNADNA sequence may influence how a gene is expressed in a cell. B Some sequences of DNADNA can interact with regulatory proteins that control transcription. C This is an inducible operon controlled by several regulatory factors. D The transcription factor may produce mutations in the binding site at the promoter sequence inhibiting the synthesis of the protein.

Some sequences of DNADNA can interact with regulatory proteins that control transcription.

Given the results shown in Figure 1, which of the following correctly describes a relationship between the two species? A Species BB is the ancestor of species AA because it has fewer bands. B Species AA is more complex than species BB because it has more bands. C Species BB has more short fragments of DNADNA than species AA does. D Species AA has more short fragments of DNADNA than species BB does.

Species BB has more short fragments of DNADNA than species AA does.

Lynch syndrome is an inherited condition associated with an increased risk for colon cancer, as well as certain other cancers. Mutations in one of several genes involved in DNA repair during DNA replication have been associated with Lynch syndrome. DNA sequencing was performed for an individual. The results indicated that the individual carries one of the dominant alleles that has been associated with Lynch syndrome. Which of the following best explains how the results should be interpreted? A The individual does not have an increased risk of developing cancer because one dominant allele is insufficient to cause the disease. B The individual has an increased risk of developing colon cancer. C Because the person's DNADNA has the mutation, other family members must have cancer. D Results cannot be interpreted until testing determines if additional mutated alleles are present.

The individual has an increased risk of developing colon cancer.

Which of the following statements is most likely to be true? A The chick and the goose have the same number of thoracic vertebrae. B The most anterior expression of Hoxc6 is the eighth vertebra in mammals. C Hoxc6 is expressed in the same embryonic segments in birds and mammals. D Hoxc6 is expressed in the same vertebra at the anterior end of all bird embryos.

The most anterior expression of Hoxc6 is the eighth vertebra in mammals.

Which of the following can best be used to justify why the GFP is expressed by E. coli cells after transformation with the plasmid? A The presence of arabinose in the nutrient agar activated the expression of the genes located downstream of the ara operon regulatory sequences. B The combination of ampicillin and arabinose in the nutrient agar inhibited the expression of certain gene products, resulting in the increased expression of the GFP. C The nutrient agar without arabinose but with ampicillin activated the expression of the genes located downstream of the ara operon regulatory sequences. D Both arabinose and ampicillin were required in the nutrient agar to activate the expression of genes located downstream of the ara operon regulatory sequences.

The presence of arabinose in the nutrient agar activated the expression of the genes located downstream of the ara operon regulatory sequences.

The following the DNA sequence is a small part of the coding (nontemplate) strand from the open reading frame of β-hemoglobin gene. Given the codon chart listed below, what would be the effect of a mutation that deletes the G at the beginning of the DNA sequence?

The reading frame of the sequence would shift, causing a change in the amino acid sequence after that point.

Which of the following normally leads to the production of functional messenger RNA in eukaryotic cells? A A decrease in the rate of ribosome synthesis B The removal of portions of RNA known as intervening sequences (introns) C A decrease in RNA polymerase activity D The replication of new messenger RNA molecules from existing messenger RNA molecules E The formation of peptide bonds between adjacent nucleotides

The removal of portions of RNA known as intervening sequences (introns)

Retroviruses such as HIV and hepatitis B virus use RNA as their genetic material rather than DNA. In addition, they contain molecules of reverse transcriptase, an enzyme that uses an RNA template to synthesize complementary DNA. Which of the following best predicts what will happen when a normal cell is exposed to a retrovirus? A The reverse transcriptase will cut the host DNADNA into fragments, destroying the host cell. B The reverse transcriptase will insert the viral RNARNA into the host's genome so it can be transcribed and translated. C The reverse transcriptase will produce DNADNA from the viral RNARNA, which can be incorporated into the host's genome and then transcribed and translated. D The reverse transcriptase will force the host ribosomes to translate the viral RNARNA prior to polypeptide assembly.

The reverse transcriptase will produce DNADNA from the viral RNARNA, which can be incorporated into the host's genome and then transcribed and translated.

Researchers claim that bacteria that live in environments heavily contaminated with arsenic are more efficient at processing arsenic into arsenite and removing this toxin from their cells. Justify this claim based on the evidence shown in Figure 1. A There are multiple operons controlling the production of proteins that process and remove arsenite from cells in both H. arsenicoxydans and O. tritici. In contrast, E. coli has only one operon devoted to arsenic removal. B Both H. arsenicoxydans and O. tritici contain the arsRarsR gene that codes for a repressor that turns on the operon to eliminate arsenite from the cell. C Both O. tritici and E. coli contain the arsDarsD gene, which codes for a protein that helps remove arsenite from the cell. D Both H. arsenicoxydans and O. tritici. have more arsenic resistance genes than has E. coli.

There are multiple operons controlling the production of proteins that process and remove arsenite from cells in both H. arsenicoxydans and O. tritici. In contrast, E. coli has only one operon devoted to arsenic removal.

Process in which RNA is produced by using a DNA template

Transcription

Use the response models shown in Figures 1 and 2 to justify the claim that phytochromes regulate the transcription of genes leading to the production of certain cellular proteins. A When inactive phytochrome PrPr is activated by red light to become phytochrome PfrPfr, it is transported into the nucleus where it binds to the transcription factor PIF3PIF3 at the promoter. This stimulates transcription, ultimately leading to protein production. Far-red light inactivates the phytochrome, which will turn transcription off by not binding to PIF3PIF3. B Far-red light activates phytochrome PrPr, causing it to travel to the nucleus where it binds to PIF3PIF3 at the promoter. This stimulates transcription, ultimately leading to protein production. Red light inactivates the phytochrome, which will turn transcription off by not binding to PIF3PIF3. C MYBMYB, and not PfrPfr, is activated by red light, causing it to bind to the promoter and stimulate transcription and translation of cellular proteins. D PIF3PIF3 binds to the promoter only in the presence of red light and PfrPfr. Any time PIF3PIF3 is bound to the promoter, MYBMYB is transcribed, initiating transcription of various other proteins in the cell.

When inactive phytochrome PrPr is activated by red light to become phytochrome PfrPfr, it is transported into the nucleus where it binds to the transcription factor PIF3PIF3 at the promoter. This stimulates transcription, ultimately leading to protein production. Far-red light inactivates the phytochrome, which will turn transcription off by not binding to PIF3PIF3.

Maximal transcription of the lac operon requires A the presence of high levels of glucose B the removal of the operator region of the operon C the presence of cyclic AMP and lactose D the activation of the repressor protein E the presence of cyclin and cyclin-dependent kinase

the presence of cyclic AMP and lactose