Bio Test 16-20
Polysomes may be defined as _____.
groups of ribosomes
What is promoter? Why TATA box is so important in promoter sequence?
A promoter is the DNA sequence where RNA polymerase attaches and initiates transcription. Promoters are only found at the head of the RNA. The TATA box is a crucial promoter DNA sequence that is involved in the process of transcription by RNA polymerase. THE TATA box its very important because it basically initiates transcription. The TATA box is found at the beginning of the promoter.
In eukaryotes, which of the following mechanisms of gene regulation operates after transcription, but before translation of mRNA into protein?
RNA splicing
Generally speaking, how many genetic codes are there?
1
The overall error rate in the completed DNA molecule is approximately _____. ( Concept 16.2) 1 error per 1,000,000,000 nucleotides 1 error per 1,000,000 nucleotides 1 error per 10,000,000,000 nucleotides 1 error per 1,000 nucleotides 1 error per 100 nucleotides
1 error per 10,000,000,000 nucleotides Correct. The rate of initial pairing errors during replication is about 1 in 100,000. This level of accuracy is then dramatically enhanced by the different proofreading mechanisms discussed in the chapter.
The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage? telomerase, primase, DNA polymerase nuclease, telomerase, primase telomerase, helicase, single-strand binding protein DNA ligase, replication fork proteins, adenylyl cyclase nuclease, DNA polymerase, DNA ligase
: nuclease, DNA polymerase, DNA ligase
E. coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment? one high-density and one low-density band one high-density and one intermediate-density band one intermediate-density band one low-density band one low-density and one intermediate-density band
: one low-density and one intermediate-density band
Which of the following human diseases is caused by a virus that requires reverse transcriptase to transcribe its genome inside the host cell?
AIDS
Which of the following is correct? ( Concept 16.1) Adenine forms two hydrogen bonds with guanine; thymine forms three hydrogen bonds with cytosine. Adenine forms three covalent bonds with thymine; guanine forms two covalent bonds with cytosine. Adenine forms two covalent bonds with thymine; guanine forms three covalent bonds with cytosine. Adenine forms two hydrogen bonds with thymine; guanine forms three hydrogen bonds with cytosine. Adenine forms three hydrogen bonds with thymine; guanine forms two hydrogen bonds with cytosine.
Adenine forms two hydrogen bonds with thymine; guanine forms three hydrogen bonds with cytosine. Correct. This is a consequence of the characteristics of the bases.
Allowing an organism to adjust to changes in environmental conditions
Altering patterns of gene expression in prokaryotes would most likely serve an organism's survival by ________.
Continuous transcription of the structural gene controlled by that regulator
A mutation that inactivates a regulatory gene of a repressible operon in E. coli cell would results in ______.
What is non-coding RNAs? What is the function of microRNAs?
A non-coding RNA is an RNA molecule that is not translated in to a protein. A significant amount f the genome may be transcribed in to non-coding RNAs (ncRNAs). There are three types of ncRNAs: 1. microRNA (miRNA): These are small single-stranded RNA molecules that can bind to mRNA. The function of this miRNAs is to degrade mRNA or block its translation. It is estimated that expression of at least half of all human genes may be regulated by miRNAs. 2. small interfering RNA (siRNA) 3. small nuclear RNA (snRNA)
Which of the following best reflects what we know about how the flu virus moves between species?
An animal such as a pig is infected with more than one virus, genetic recombination occurs, the new virus mutates, the virus is passed to a new species such as a bird, and the virus mutates again and can now be transmitted to humans.
21. A primary transcript in the nucleus of a eukaryotic cell is _____ the functional mRNA, while a primary transcript in a prokaryotic cells is _____ the functional mRNA.
B) larger than; the same size as
18. Alternative RNA splicing ____.
B) can allow the production of proteins of different sizes and function from a single mRNA.
Who formulated the one gene-one enzyme hypothesis?
Beadle and Tatum
24. Which of the following is the first event to take place in translation in eukaryotes?
D) the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA
A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture? nucleotides Okazaki fragments DNA polymerase DNA ligase primase
DNA ligase
What enzyme joins Okazaki fragments? ( Concept 16.2) DNA polymerase DNA ligase helicase topoisomerase primase
DNA ligase Correct. Helicases unwind the DNA; polymerase synthesizes the complementary strands; ligase joins the Okazaki fragments.
epigenetic phenomena
DNA methylation and histone acetylation are examples of ________.
What is DNA methylation?
DNA methylation is a biochemical
The removal of the RNA primer and addition of DNA nucleotides to the 3' end of Okazaki fragments in its place is carried out by _____. ( Concept 16.2) nuclease primase DNA polymerase I DNA polymerase III ligase
DNA polymerase I Correct. Upon encountering the RNA primer, DNA polymerase III falls off the DNA and is replaced by DNA polymerase I.
What is the function of reverse transcriptase in retroviruses?
It uses viral RNA as a template for DNA synthesis
Draw & Label the lytic cycle and lysogenic cycle.
Lytic Cycle (AESSR). 1. Attachment 2. Entry 3. Synthesis 4. Self-assembly 5. Release Lysogenic Cycle Daughter Cell with prophage Prophage exits chromosome Phage DNA integrates in to bacterial chromosome Prophage is copied with bacterial chromosome Many cell divisions create many infected bacteria
Which one of the following statements is true? : -Each DNA base codes for three amino acids. -Each gene codes for three proteins. -It takes three genes to code for one protein. -Each triplet has many different meanings. -Each amino acid in a protein is coded for by three bases in the DNA.
Each amino acid in a protein is coded for by three bases in the DNA.
stimulate normal cell growth and division
Proto-oncogenes ______.
Genetic information of eukaryotic cells is transferred from the nucleus to the cytoplasm in the form of _____.
RNA
alternative splicing
Not long ago, it was believed that a count of the number of protein-coding genes would provide a count of the number of proteins produced in any given eukaryotic species. This is incorrect, largely due to the discovery of widespread ________.
When genes are expressed, they produce _____.
RNA molecules and polypeptides
Which one of the following catalyzes the linkage between ribonucleotides to form RNA during gene expression?: -RNA polymerase -RNA ligase -a ribozyme -reverse transcriptase -tRNA
RNA polymerase
Which of the following components is required for DNA replication? ( Concept 16.2) proteases sucrases ribosomes transfer RNA RNA primer
RNA primer Correct. In the cell, the preexisting chain, the primer needed to initiate DNA elongation, is RNA, not DNA.
binding to intracellular receptors and promoting transcription of specific genes
Steroid hormones produce their effects in cells by ______.
One strand of a DNA molecule has the base sequence 5′-ATAGGT-3′. The complementary base sequence on the other strand of DNA will be 3′-_____-5′. ( Concept 16.2) TGGATA TATCCA UAUCCA ATAGGT TGGAUA
TATCCA Correct. A always pairs with T, and G with C.
What is "Central Dogma"? How do you explain it?
The central dogma is the concept that cells are governed by a cellular chain of command. The central dogma is the process by which the instructions in DNA are converted in to a functional product. It was first proposed in 1958 by Francis Crick the discoverer of the structure of DNA. The central dogma of molecular biology explains the flow of genetic information from DNA to RNA to make a protein. DNA is the bridge between genes and proteins. DNA -> RNA -> Protein.
The cyclic AMP and lactose levels are both high within the cell
The lactose operon is likely to be transcribed when_____.
sets of regulatory proteins
The reason for differences in the sets of proteins expressed in a nerve and a pancreatic cell of the same individual is that nerve and pancreatic cells contain different _______.
Which of the following represents a difference between viruses and viroids?
Viruses have capsizes composed of protein, whereas viroids have no capsids
Who is credited with explaining the structure of the DNA double helix? ( Concept 16.1) Jacob and Monod Avery, McCarty, and MacLeod Watson and Crick Hershey and Chase Griffith
Watson and Crick Correct. In April 1953, Watson and Crick published a one-page paper in the journal Nature elucidating their molecular model for the DNA double helix.
Continuous transcription of the operon's genes
What would occur if the repressor of an inducible operon were mutated so that it could not bind the operator?
non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function
Which of the following could account for much of the DNA that is not coding for proteins?
What technique was most helpful to Watson and Crick in developing their model for the structure of DNA? ( Concept 16.1) X-ray crystallography radioactive labeling transgenic animals cloned DNA electrophoresis
X-ray crystallography Correct. Watson and Crick based their model of DNA on insights they were able to gain from Franklin's X-ray diffraction photo.
Inducer
Which of the following, when taken up by a cell, binds to a repressor so that the repressor no longer binds to the operator?
Which of the following supports the argument that viruses are nonliving?
They are not cellular
Which one of the following types of mutation is least likely to affect the function of the protein corresponding to the gene in which the mutation occurs?
base-pair substitution
What is a post-translational modification of a polypeptide?
cleavage of a polypeptide into two or more chains
Which of the following is characteristic of the lytic cycle?
a large number of phages are released at a time
In many ways, the regulation of the genes of a particular group of viruses will be similar to the regulation of the host genes. Therefore, which of the following would you expect of the genes of a bacteriophage?
control of more than one gene in an operon
At each end of a DNA replication bubble is _____. ( Concept 16.2) a telomere a gene a replication fork a ribosome an origin of replication
a replication fork Correct. Replication forks are found at the ends of replication bubbles.
A geneticist found that a particular mutation had no effect on the polypeptide encoded by the gene. This mutation probably involved _____
a silent or neutral mutation
In DNA, the two purines are _____, and the two pyrimidines are _____. ( Concept 16.1) adenine and thymine ... cytosine and guanine adenine and cytosine ... guanine and thymine cytosine and guanine ... adenine and thymine cytosine and thymine ... adenine and guanine adenine and guanine ... cytosine and thymine
adenine and guanine ... cytosine and thymine Correct. Purines have two rings, and pyrimidines have one.
In transcription, _____.: -the promoter region acts as an initial binding site for RNA polymerase -only one of the DNA strands is used as the template -the RNA nucleotides used are produced by the cell -all of the above -none of the above
all of the above
What is difference between an epidemic and a pandemic?
an epidemic is restricted to a local region; a pandemic is global
During the transcription of a given portion of a DNA molecule _____.
mRNA is synthesized on only one of the chains
A virus infects a cell and randomly inserts many short segments of DNA containing a stop codon throughout the organism's chromosomes. This will probably cause _____.
manufactured proteins to be short and defective
The bonds that hold tRNA molecules in the correct three-dimensional shape are _____.
hydrogen bonds
At one point as a cell carried out its day-to-day activities, the nucleotides GAT were paired with the nucleotides CUA. This pairing occurred _____.
during transcription
A point mutation in which a single base pair is inserted or deleted from DNA is called a(n) _____
frame-shift mutation
Telomeres _____. ( Concept 16.2) get shorter with continued cell division are shorter for younger individuals remain the same regardless of the frequency of cell division are found in both prokaryotic and eukaryotic cells get longer with continued cell division
get shorter with continued cell division Correct. However, the enzyme telomerase, which is not present in most cells of multicellular organisms, can lengthen the telomeres.
Which of the following can be effective in preventing the onset of viral infection in humans?
getting vaccinated
In the figure, at the arrow marked II, what enzyme(s) are being utilized?
host cell DNA polymerase
Effective antiviral drugs are usually associated with which of the following properties?
interference with viral replication
Telomerase _____. ( Concept 16.2) is an enzyme that lengthens telomeres slows the rate of cancer cell growth splits telomeres speeds cell aging prevents the loss of centromeric DNA
is an enzyme that lengthens telomeres Correct. Telomerase is an enzyme made of a protein and an RNA sequence that serves as a template for adding additional telomeric DNA sequences. Telomerase is found in germ cells and in many human cancers, increasing the longevity of these cells.
The first amino acid inserted into a new polypeptide chain in eukaryotic cells is always _____.
methionine
The "beads on a string" seen in interphase chromatin are _____. ( Concept 16.3) looped domains heterochromatin histone tails nucleoids nucleosomes
nucleosomes Correct. Nucleosomes are complexes of DNA wrapped around eight histone molecules.
Monomers for the synthesis of DNA are called _____. ( Concept 16.1) disaccharides nucleotides monosaccharides fatty acids amino acids
nucleotides Correct. Each nucleotide unit of DNA consists of a nitrogenous base (A, G, C, or T), the sugar deoxyribose, and a phosphate group.
The structures called snRNPs are _____.
part of a spliceosome
During translation in a eukaryotic cell _____.
polypeptides are synthesized at ribosomes, according to instructions carried by mRNA
One strand of a DNA molecule has the following sequence: 3'-AGTACAAACTATCCACCGTC-5'. In order for transcription to occur in that strand, there would have to be a specific recognition sequence, called a(n) _____, to the left of the DNA sequence indicated
promoter
In many cases, more than one codon codes for the same amino acid. Because of this, we say that the code is _____.
redundant
The experiments of Meselson and Stahl showed that DNA _____. ( Concept 16.2) is the genetic material codes for the sequence of amino acids in proteins contains complementary base pairing is composed of nucleotides replicates in a semiconservative fashion
replicates in a semiconservative fashion Correct. In the semiconservative model of DNA replication, the two strands of the parental molecule separate. Each functions as a template for the synthesis of a new complementary strand.
Why do RNA viruses appear to have higher rates of mutation?
replication of their genomes does not involve proofreading
Which viruses have single‐stranded RNA that acts as a template for DNA synthesis?
retroviruses
Nuclei of eukaryotic cells contain spliceosomes that are made up of _____.
snRNA and protein
Cells are able to distinguish proteins destined for secretion or for segregation to specific intracellular compartments from those that will remain in the cytoplasm because
some proteins, as they begin to be synthesized, contain a signal region that causes the ribosome with its growing polypeptide to attach to the ER and translocate the polypeptide into the lumen (space) of the ER
The virus genome and viral proteins are assembled into virions (virus particles) during _____.
the lytic cycle only
The host range of a virus is determined by _____.
the proteins on its surface and that of the host
Chargaff found that for DNA _____. ( Concept 16.1) the ratio of A to G is close to 1:1 and the ratio of T to C is close to 1:1 the ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1 A + T = 50% of the total bases the ratio of A to C is close to 1:1 and the ratio of G to T is close to 1:1 A + T = G + C
the ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1
During translation, amino acid chain elongation occurs until _____.
the ribosome encounters a "stop" codon
The information in DNA is contained in _____. ( Concept 16.1) the sequence of nucleotides along the length of the two strands of the DNA molecule the types of sugars used in making the DNA molecule the variation in the structure of nucleotides that make up the DNA molecule the sequence of amino acids that makes up the DNA molecule All of the listed responses are correct.
the sequence of nucleotides along the length of the two strands of the DNA molecule Correct. Although base-pairing rules dictate the combinations of nitrogenous bases forming the rungs of the double helix, they do not restrict the sequence of nucleotides along each strand, and the linear sequence of bases can be varied in countless ways.
The unwinding of DNA at the replication fork causes twisting and strain in the DNA ahead of the fork, which is relieved by an enzyme called _____. ( Concept 16.2) relievase primase ribosomes topoisomerase ligase
topoisomerase Correct. Topoisomerase cuts the DNA and allows it to spin around its central axis, which relieves the strain caused by twisting.
Some viruses can be crystallized and their structure analyzed. One such virus is yellow mottle virus, which infects beans. This virus has a single-stranded RNA genome containing about 6300 nucleotides. Its capsized is 25-30nm in diameter and contains 180 identical capsomeres. If the yellow mottle virus begins its infection of a cell by using its genome as mRNA, which of the following would you expect to be able to measure?
translation rate
22. A particular triple of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is ____.
D) AAA
The P site of a ribosome does which one of the following?
It holds the tRNA carrying the growing polypeptide chain.
Starts when the pathway's substrate is present
Transcription of a structural gene in an inducible operon ____.
encode proteins that help prevent uncontrolled cell growth
Tumor-Suppressor genes ________.
When RNA is being made, the RNA base _____ always pairs with the base _____ in DNA.
U; A
Are viruses generally considered living or non-living? Explain.
Viruses are generally considered non-living unless they are inside a host cell. Viruses are not considered living organisms because they need a host to reproduce. They aren't made of cells and they can't metabolize or grow on their own.
Describe briefly the three stages of transcription.
1. Transcription is when the information in DNA is transferred to the mRNA. Transcription I (Initiation) is when the enzyme RNA polymerase unzips the DNA molecule. Transcription II (Elongation) is where the free RNA nucleotides form base pairs with their complementary nucleotides of DNA. Transcription III (Termination) is when the completed RNA (mRNA) strand leaves the nucleus of the cell and enters the cytoplasm where it will attach to ribosomes and create proteins. Transcription is the first stages of gene expression.
What is the proper order of the following events in the expression of a eukaryotic gene? 1. translation 2. RNA processing 3. transcription 4. modification of protein
3, 2, 1, 4
The number of nucleotide bases "read" together on the mRNA to designate each amino acid is _____; this unit is called a(n) _____.
3; codon
DNA polymerase adds nucleotides to the _____ of the leading strands, and to the _____ of the lagging strands (Okazaki fragments). ( Concept 16.2) 5′ end ... 3′ end sugar group ... phosphate group 3′ end ... 3′ end 3′ end ... 5′ end 5′ end ... 5′ end
3′ end ... 3′ end Correct. Although the leading strand and lagging strand are synthesized in opposing directions with respect to the movement of the replication fork, the DNA polymerase enzyme can only add nucleotides to the 3′ end of a growing DNA strand.
In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules? G = T A = G A + T = G + T A = C A + G = C + T
A + G = C +
produces proteins specific to a particular cell type
A Cell is considered to be differentiated when it _______.
Co-repressor
A lack of which molecule would result in a cell's inability to "turn off" genes?
1. A particular Triplet of bases in the template strand of DNA is 5' AGT to 3'. The corresponding codon for the mRNA transcribed is_____.
A) 3' UCA 5'
2. The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?
A) A gene from an organism can theoretically be expressed by any other organism.
15. Which of the following best describes the significance of the TATA box in eukaryotic promoters?
A) It is the recognition site for a specific transcription factor
26. The release factor (RF) ____
A) binds to the stop codon in the A site in place of a tRNA
30. Once a peptide has been formed between the amino acid attached to the tRNA in the P site and the amino acid associated with the tRNA in the A site, what occurs next?
A) translocation
Which of the following statements about replication origins is correct? ( Concept 16.2) In bacteria, the DNA sequence at the origin is recognized by specific proteins that then bind to the origin. The two strands of DNA at the origin are separated, allowing the formation of a replication bubble. In both prokaryotes and eukaryotes, replication proceeds in both directions from each origin. Bacterial chromosomes have a single origin, but eukaryotic chromosomes have many origins. All of the listed responses are correct.
All of the listed responses are correct.
Individuals with the disorder xeroderma pigmentosum _____. ( Concept 16.2) have difficulty repairing thymine dimers often have inherited defects in the nucleotide excision repair system have high rates of skin cancer are hypersensitive to sunlight All of the listed responses are correct.
All of the listed responses are correct. Correct. Individuals with this disorder are unusually sensitive to sunlight because they cannot repair the thymine dimers that can result from exposure to ultraviolet light.
Why were many of the early experiments on DNA carried out on viruses and bacteria? ( Concept 16.3) They have short generation times. They can interact with each other. They have relatively small genomes. Their chromosomes have a simpler structure. All of the responses are true.
All of the responses are true. Correct. Experiments on DNA were, and still are, carried out on these subjects for all of these reasons.
piRNA
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 ______.
enzyme A enzyme B A---------->B--------->C 3. The figure above shows a simple metabolic pathway. According to Beadle and Tatum's hypothesis, how many genes are necessary for this pathway?
B) 2
32. How does termination of translation take place?
B) A stop codon is reached
8. Once researchers identified DNA as the unit of inheritance, they asked how information was transferred from the DNA in the nucleus to the site of protein synthesis in the cytoplasm. What is the mechanism of information transfer in eukaryotes?
B) Messenger RNA is transcribed from a single gene and transfer information from the DNA in the nucleus to the cytoplasm, where protein synthesis takes place.
5. In the process of transcription, ___________.
B) RNA is synthesized
13. In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a global protein?
B) RNA polymerase II
12. Which of the following statements best describes the termination of transcription in prokaryotes?
B) RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript.
20. Which one of the following statements about RNA processing is true?
B) Ribozymes may function in RNA splicing.
17. A ribozyme is _____.
B) an RNA with catalytic activity.
11. Which of the following occurs in prokaryotes but not in eukaryotes?
B) concurrent transcription and translation
27. What type of bonding is responsible for maintaining the shape of the tRNA molecule shown in the figure above?
B) hydrogen bonding between base pairs
6. Codons are part of the molecular structure of ________.
B) mRNA
33. Which of the following statements is true about protein synthesis in prokaryotes?
B) translation can begin while transcription is still in progress
What is the major difference between bacterial chromosomes and eukaryotic chromosomes? ( Concept 16.3) Bacterial chromosomes have much more protein associated with the DNA than eukaryotes. There is no difference between bacterial and eukaryotic chromosomes. Bacteria have a single circular chromosome whereas eukaryotes have several linear chromosomes. The DNA of bacterial chromosomes has a slightly different structure. Eukaryotes have a single circular chromosome whereas bacteria have several linear chromosomes.
Bacteria have a single circular chromosome whereas eukaryotes have several linear chromosomes. Correct. The arrangement of DNA and its association with proteins is different for prokaryotes and eukaryotes.
In a comparison between asexually reproducing bacteria and sexually reproducing multicellular eukaryotes, uncorrected errors in replication are more likely to be transmitted to subsequent generations in bacteria than in multicellular eukaryotes. Which of the following provides the best evidence-based explanation for this difference?( Concept 16.2) Although the genome for each is represented as pairs of homologous chromosomes, errors in bacteria affect both homologs, but only one is affected in eukaryotes. Unlike multicellular eukaryotes, bacteria lack DNA repair enzymes, so there are just more uncorrected errors at play. Being asexual and single-celled, all uncorrected errors of replication in bacteria are transmitted to subsequent generations. Multicellular eukaryotes typically reproduce sexually, so uncorrected errors are transmitted only if they occur in germ cells that meiotically divide to produce gametes. Only errors that lead to faster growing strains are left uncorrected in bacteria, whereas all errors are detected and repaired in multicellular eukaryotes. The third and fourth listed responses can explain this phenomenon.
Being asexual and single-celled, all uncorrected errors of replication in bacteria are transmitted to subsequent generations. Multicellular eukaryotes typically reproduce sexually, so uncorrected errors are transmitted only if they occur in germ cells that meiotically divide to produce gametes. Correct. Uncorrected errors in dividing somatic cells of multicellular eukaryotes may lead to problems in individuals, but they will not be transmitted to offspring. In bacteria, however, all uncorrected errors are transmitted to subsequent generations because cell division equates to reproduction in single-celled organisms.
What is the difference between exon and intron?
Both exon and introns are found on genes. The difference between exons and introns is that exons are the coding parts of a gene that will ultimately become a part of the final mature RNA. Introns are any part of the gene that will NOT become a part of the final mature RNA. The introns are the non coding sections of DNA and are removed from the gene during RNA splicing. The introns are the "junk" and are excreted through stool and urine.
In what way(s) is our traditional representation of DNA polymerase molecules moving like locomotives along a track inaccurate? ( Concept 16.2) The proteins involved in replication do not move; instead, DNA is drawn through the complex. DNA polymerase acts as part of a large complex of proteins, not like a single locomotive. Like a train on a track, DNA polymerase must add nucleotides sequentially. It cannot jump around. Both the first and second answers are correct. DNA polymerase completes replication of one strand and then begins the other.
Both the first and second answers are correct. Correct. DNA polymerase is part of a replication machine that may be anchored to the nuclear matrix. DNA is drawn into the complex, and the newly synthesized strands are extruded.
34. Of the following, which is the most current description of a gene?
C) A DNA suquence that is expressed to form a functional product: either RNA or polypeptide
16. Which of the following does not occur in prokaryotic gene expression, but does occur in eukaryotic gene expression?
C) A cap is added to the 5' end of the mRNA.
29) During elongation, which site in the ribosome represents the location where a codon is being read?
C) A site
31. Which one of the following, if missing, would usually prevent translation from starting?
C) AUG codon
9. According to the central dogma, what molecule should go in the blank? DNA-> ______ -> Proteins
C) mRNA
28. Translation requires _____.
C) mRNA, tRNA & rRNA
25. A signal peptide ______.
C) helps target a protein to the ER
14. Transcription in eukaryotes requires which of the following in addition to RNA polymerase?
C) several transcription factors
4. Which of the following is directly related to a single amino acid?
C) the three-base sequence of mRNA
19. In the structural organization of many eukaryotic genes, individual eons may be related to which of the following?
C) the various domains of the polypeptide product
10. Codons are three-base sequences that specify the addition of a single amino acid. How do eukaryotic codons and prokaryotic codons compare?
D) Codons are a nearly universal language among all organisms.
7. What does it mean when we say the genetic code is redundant?
D) More than one codon can specify the addition of the same amino acid.
23. Accuracy in the translation of mRNA into the primary structure of a polypeptide depends not he specificity in the ______.
D) binding of the anticodon to the codon and the attachment of amino acids to tRNAs.
What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized? Polymerase can work on only one strand at a time. DNA ligase works only in the 39 S59 direction. The origins of replication occur only at the 59 end. DNA polymerase can join new nucleotides only to the 39 end of a growing strand. Helicases and single-strand binding proteins work at the 59 end.
DNA polymerase can join new nucleotides only to the 39 end of a growing strand.
A cell biologist found that two different proteins with largely different structures were translated from two different mRNAs. These mRNAs, however, were transcribed from the same template within the cell nucleus. Which mechanism below could best account for this?
Exons from the same gene could be spliced in different ways to make different mRNAs.
reducing the levels of intracellular cAMP
Extracellular glucose inhibits transcription of the lac operon by ________.
RNA polymerase must bind to the promoter, and the repressor must be inactive.
For a repressible operon to be transcribed, which of the following must occur?
Why HIV is called a retrovirus?
HIV is called a retrovirus because it is a virus consisting of a ssRNA which is transcribed into complementary DNA. HIV is called a retrovirus because it does the same thing as a virus, but does a reverse transcription. After entering the host cell, the RNA from the virus can change the DNA strand in the host cell. Then as the DNA is transcribed and translated in to proteins, it makes new virus particles.
Why do scientists consider HIV to be an emerging virus?
HIV suddenly became apparent and widespread int he 1980s
Which description of DNA replication is correct? ( Concept 16.2) Ligase assembles single-stranded codons, then polymerase knits these codons together into a DNA strand. The two strands of DNA separate, and restriction enzymes cut up one strand. Then, the DNA polymerase synthesizes two new strands out of the old ones. Helicases separate the two strands of the double helix, and DNA polymerases then construct two new strands using each of the original strands as templates. The two strands separate, and each one receives a complementary strand of RNA. Then this RNA serves as a template for the assembly of many new strands of DNA. Ligase separates the two strands of the DNA double helix. Then, DNA polymerase synthesizes the leading strand and primase synthesizes the lagging strand.
Helicases separate the two strands of the double helix, and DNA polymerases then construct two new strands using each of the original strands as templates. Correct. In the semiconservative model of DNA replication, the two strands of the parental molecule separate, and each functions as a template for the synthesis of a new complementary strand.
Which of the following processes within viral replication is the greatest source of genetic variation in RNA virus populations?
High mutation rate due to lack of proofreading of RNA genome replication errors.
What is histone and chromatin?
Histones are alkaline proteins that package and order the DNA into structural units. Chromatin is the combination of DNA and proteins that make up the contents of the nucleus in a cell. The structural organization of chromatin helps regulate gene expression in several ways. Chemical modifications of histone and chromatin influence both chromatin structure and gene expression.
Which of the three types of viruses shown above would you expect to include glycoproteins?
I and II only
Which of the three types of viruses shown above would you expect to include a capsid(s)?
I, II and III
Refer to the treatments listed below to answer the following question(s). You isolate an infectious substance capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium, virus, viroid, or prion. You have four methods at your disposal to analyze the substance and determine the nature of the infection again. I. Treat the substance with enzymes that destroy all nucleic acids and then determine whether the substance is still infectious. II. Filter the substance to remove all elements small than what can be easily seen under a light microscope. III. Culture the substance on nutritive medium, away from any plant cells. IV. Treat the sample with proteases that digest all proteins and then termite whether the substance is still infectious. If you already know that the infection agent was either bacterial or viral, which method(s) listed above would allow you to distinguish between these two possibilities?
II or III
On the off chance that you might contract an archaeal infection, how might it be treated?
If you were infected by an archaeal organism, you would probably baffle the doctor. so no treatment
Which of the following best illustrates the importance of altered DNA nucleotides in evolutionary processes?( Concept 16.2) In a temporally variable environment, a population of bacteria with an elevated rate in replication error can have a selective advantage over other populations with lower rates in replication error. Natural selection will always select to reduce rates of replication errors within populations. A population of bacteria with an elevated rate of replication error is always eliminated by natural selection. In a temporally stable environment, a population of bacteria with an elevated rate in replication error has a selective advantage over other species with reduced rates in replication error. A population of bacteria with a very low rate of replication error always has an evolutionary advantage over other populations with higher rates.
In a temporally variable environment, a population of bacteria with an elevated rate in replication error can have a selective advantage over other populations with lower rates in replication error. Correct. In an environment that undergoes rapid change over time, an elevated rate of mutations due to uncorrected errors in replication can be advantageous if such errors generate greater phenotypic variation in the population and thus greater likelihood that some individuals in the population will be well matched to the prevailing environmental conditions.
binds to other proteins or to the TATA box
In eukaryotes, general transcription factors ______.
a decrease in glucose and increase in cAMP
In postitive control of several sugar-metabolism related operons, the catabolite activator protein (CAP) binds to DNA to stimulate transcription. What causes an increase in CAP activity in stimulating transcription?
What is a key difference in gene expression between eukaryotic and prokaryotic cells?
In prokaryotic cells, the mRNA transcript is immediately available as mRNA without processing.
Use the following information to answer the question(s) below. The herpes viruses are important enveloped DNA viruses that cause diseases in vertebrates and in some inter vertebrates such as oysters. Some of the human forms are herpes simplex virus (HSV) types I and II, causing facial and genital lesions, and the varicella zoster virus (VSV), causing chicken pox and shingles. Each of these three actively infects nervous tissue. Primary infections are fairly mild, but the virus is not then cleared from the host; rather, viral genomes are maintained in cells in a latent phase. The virus can later reactivate, replicate again, and infect others. If scientists are trying to use what they know about HSV to devise a means of protecting other people from being infected, which of the following would have the best chance of lowering the number of new cases of infection.
Interfere with new viral replication in preexisting cases of HSV
Which one of the following statements correctly describes mRNA processing?
Introns are cut out of the primary transcript, and the resulting exons are spliced together.
summarize protein synthesis
Messenger RNA is made on a DNA template, and then amino-acid-bearing transfer RNAs bind to it through codon-anticodon pairing.
Inducer
Most repressor proteins are allosteric. Which of the following binds with the repressor to alter its conformation?
Will treating a viral infection with antibiotics affect the course of the infection?
No; antibiotics work by inhibiting enzymes specific to bacteria. Antibiotics have no effect on eukaryotic or virally encoded enzymes.
compare the sequences of different mRNAs made from the given gene
One way to detect alternative splicing of transcripts from a given gene is to _______.
Compare the effect on the host of lytic (virulent) phase and a lysogenic phase.
Phages have two alternative replication mechanisms: the Lytic Cycle & the lysogenic cycle. The lytic cycle is a phage replication cycle that ultimately leads to the death of the host cell. The lytic cycle produces new phages and lyses the hosts cell wall, releasing the progeny viruses. A phage that reproduces only by the lytic cycle is called a virulent phage. The lysogenic cycle replicates the phage genome WITHOUT destroying the host cell. The viral DNA molecule from the phage is incorporated in to the host cell's chromosome. The integrated viral DNA is known as a prophage.
In 2009, a flu pandemic was believed to have originated when viral transmission occurred from pig to human, thereby earning the designation, "swine flu." Although pigs are thought to have been the breeding ground for the 2009 virus, sequences from bird, pig and human viruses were all found within this newly identified virus. What is the most likely explanation of why this virus contained sequences from bird, pig, and human viruses?
Related viruses can undergo genetic recombination if the RNA genomes mix and match during viral assembly.
Once the DNA at the replication fork is unwound by helicases, what prevents the two strands from coming back together to re-form a double helix? ( Concept 16.2) One of the strands is rapidly degraded, preventing the double helix from re-forming. The helicase pushes the two strands so far apart that they have no chance of finding each other. DNA polymerase follows the helicase so closely that there is no chance for the strands to come back together. Single-strand binding proteins bind the unwound DNA and prevent the double helix from re-forming. The helicase modifies the DNA in such a way as to eliminate the affinity between the two strands.
Single-strand binding proteins bind the unwound DNA and prevent the double helix from re-forming. Correct. As soon as the helicase passes, the single-strand binding proteins rapidly coat the unwound DNA and prevent the strands from coming back together.
HIV is inactivated in the laboratory after a few minutes of sitting at room temperature, but the flu virus is still active after sitting for several hours. What are the practical consequences of these findings?
The flu virus can be transmitted more easily from person to person than HIV
Gene is the molecular unit of heredity. Explain it.
The gene is the molecular unit of heredity because the DNA inherited by an organism leads to specific traits. DNA dictates the synthesis of proteins and of RNA molecules involved in protein synthesis. Gene expression is the process by which DNA directs the synthesis of proteins. The expression of genes that code for proteins includes transcription and translation.
RNA interference
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 _______.
are at considerable distances from the promoter; promoter-proximal elements are close to the promoter
The primary difference between enhancers and promoter-proximal elements is that enhancers ______.
inhibits the cell cycle
The product of the p53 gene _______.
What is a ribosome? Briefly describe the three binding sites of a ribosome.
The ribosome is a complex molecular machine, found within all living cells, that serves as the site of biological protein synthesis. Ribosomes link amino acids together in the order specified by mRNA. Ribosomes are composed of two subunits, one small & one large. Four binding sites are located on the ribosome: One for mRNA and three for tRNA. After transcription, the mRNA leaves the nucleus and bonds with a ribosome. The three tRNA are labeled P, A and E. The P site binds to the tRNA holding the growing polypeptide chain of amino acids. The A site binds to the aminoacyl tRNA which old the new amino acid to be added to the polypeptide chain.The E site serves as a threshold, the final transitory step before a tRNA is let go by the ribosome.
If a viral host cell has a mutation that interferes with the addition of carbohydrates to proteins in the Golgi, which of the following could likely result?
The viral envelope proteins would not be glycosylated and might not arrive at the most plasma membrane.
Viruses use the host's machinery to make copies of themselves. However, some human viruses require a type of replication that humans do not normally have. For example, humans normally do not have the ability to convert RNA into DNA. How can these types of viruses infect humans, when human cells cannot perform a particular role that the virus requires?
The viral genome codes for specialized enzymes not in the host
It cannot bind to the inducer
There is a mutation in the repressor that results in a molecule known as a super-repressor because it surpasses the lac operon permanently. Which of these would characterize such a mutant?
A person is most likely to recover from a viral infection if the infected cells _____.
can undergo normal cell division
Viruses replicate only in host cells. Briefly explain it.
Viruses are intracellular parasites which can only express their genes and reproduce within a living cell/host because it uses the host cells organelles to reproduce. Viruses use host cell resources such as enzymes, ATP, etc. to replicate the viral genome and viruses cannot reproduce or carry out metabolism outside of a host cell.
A double- stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA
Which of the following best describes siRNA?
Repressor: The repressor prevents gene transcription by binding to the operator and blocking RNA polymerase.
Which of the following is a protein produced by a regulator gene?
The genes share a single common enhancer, which allows appropriate activators to turn on their transcription at the same time
Which of the following mechanisms is (are) used to coordinate the expression of multiple, related genes in eukaryotic cells?
a mutation that greatly increases the amount of photo-oncogene protein
Which of the following types of mutation would convert a photo-oncogene into an oncogene?
The difference between vertical and horizontal transmission of plant viruses is that vertical transmission is ________.
a transmission virus from a parent plant to its progeny, and horizontal transmission is one plant spreading the virus to another plant
Which of the following viruses would most likely have reverse transcriptase?
an RNA-based lysogenic virus
Transcription factors are found in __________.
archaea and eukaryotes
How many nucleotides are needed to code for a protein with 450 amino acids?
at least 1,350
The role of DNA polymerases in DNA replication is to _____. ( Concept 16.2) link together short strands of DNA attach free nucleotides to the new DNA strand synthesize an RNA primer to initiate DNA strand synthesis separate the two strands of DNA All of the listed responses are correct.
attach free nucleotides to the new DNA strand Elongation of new DNA at a replication fork is catalyzed by enzymes called DNA polymerases.
The trp (Tryptophan) repressor blocks transcription of the trp operon when the repressor _______.
binds to tryptophan
The first class of drugs developed to treat AIDS, such as AZT, were known as reverse transcriptase inhibitors. They worked because they _______.
bonded to the viral reverse transcriptase enzyme, thus preventing the virus from making a DNA copy of its RNA genome
The DNA structures of prokaryotes and eukaryotes are different in several ways, but one way in which they are the same is that _____. ( Concept 16.2) the DNA is packaged into several linear chromosomes most of the DNA is in the form of plasmids both have a single circular chromosome histones are present in the nucleosomes both have a sugar-phosphate backbone
both have a sugar-phosphate backbone Correct. All DNA occurs as a double helix with two sugar-phosphate backbones that are antiparallel to each other.
During the replication of DNA, _____. ( Concept 16.2) errors never occur the cell undergoes mitosis both strands of a molecule act as templates the reaction is catalyzed by RNA polymerase only one strand of the molecule acts as a template
both strands of a molecule act as templates Correct. When a cell copies a DNA molecule, each strand serves as a template for ordering nucleotides into a new complementary strand.
The incorporation of an incorrect base into the DNA during replication _____. ( Concept 16.2) is virtually impossible, as the accuracy of DNA polymerase is such that errors almost never occur will almost certainly lead to the death of the cell can be repaired by the mismatch repair system will trigger the cell to destroy the new strand, and replication will begin again cannot be repaired, and a new mutation will invariably result
can be repaired by the mismatch repair system Correct. The mismatch repair system can detect and rectify incorrectly incorporated bases.
Viral infections in plants _____.
can spread within a plant via plasmodesmata
Unlike prokaryotic DNA replication, replication of eukaryotic chromosomes _____. ( Concept 16.2) cannot be completed by DNA polymerase has a single origin is semiconservative involves two leading strands and no lagging strands is error free
cannot be completed by DNA polymerase Correct. This is the case because eukaryotic chromosomes are linear, and DNA polymerase cannot replicate the extreme 3' end of the template strands.
Ultraviolet (UV) radiation is damaging to cells because it _____.
causes mutations in the DNA
Which of the following accounts for someone who has had regular herpesvirus‐mediated cold sore or genital sore flare-ups?
copies of the herpesvirus genome permanently maintained in host nuclei
The function of tRNA during protein synthesis is to _____.
deliver amino acids to their proper site during protein synthesis
The elongation of the leading strand during DNA synthesis progresses away from the replication fork. produces Okazaki fragments. occurs in the 39 S59 direction. does not require a template strand. depends on the action of DNA polymerase.
depends on the action of DNA polymerase.
A researcher lyses a cell that contains nucleic acid molecules and capsomeres of tobacco mosaic virus (TMV). The cell contents are left in a covered test tube overnight. The next day this mixture is sprayed on tobacco plants. We expect that the plants would _______.
develop the typical symptoms of TMV infection
What is the main structural difference between enveloped and nonenveloped viruses?
enveloped viruses have a phospholipid membrane outside their capsized, whereas non enveloped do not have a phospholipid membrane
Usually, in eukaryotic genes _____.
exons are transcribed, but the RNA transcribed from introns does not leave the nucleus
During Griffith's experiments with Streptococcus pneumoniae in mice, material from _____ bacteria transformed _____ bacteria. ( Concept 16.1) heat-killed nonvirulent ... living virulent heat-killed virulent ... living nonvirulent living nonvirulent ... heat-killed virulent living virulent ... heat-killed nonvirulent living nonvirulent ... living virulent
heat-killed virulent ... living nonvirulent Correct. Griffith found that some of the living nonvirulent cells were converted to the virulent form.
After the formation of a replication bubble, which of the following is the correct sequence of enzymes used for the synthesis of the lagging DNA strand? ( Concept 16.2) helicases, primase, DNA polymerases, ligase helicases, primase, ligase, DNA polymerases primase, helicases, DNA polymerases, ligase ligase, primase, DNA polymerases, helicases helicases, DNA polymerases, primase, ligase
helicases, primase, DNA polymerases, ligase Correct. First the double helix is unwound; primase makes the RNA primer; DNA polymerases elongate the growing strand and replace the RNA primer with DNA; and DNA ligase joins the Okazaki fragments.
In a nucleosome, the DNA is wrapped around histones. a thymine dimer. ribosomes. polymerase molecules. satellite DNA.
histones.
The two sugar-phosphate strands that form the rungs of a DNA double helix are joined to each other through _____. ( Concept 16.1) 5' deoxyribose and phosphate bonds covalent bonds between nitrogen atoms in adenine and in thymine covalent bonds between carbon atoms in deoxyribose molecules ionic bonds between guanine and cytosine hydrogen bonds between nucleotide bases
hydrogen bonds between nucleotide bases Correct. The two sugar-phosphate strands of a DNA molecule are held together by hydrogen bonding between the nitrogenous bases, which are paired in the interior of the helix.
In eukaryotic cells, a terminator in mRNA synthesis is _____.
in the nucleus
Which of the following attributes of DNA is most crucial to its accurate duplication? ( Concept 16.2) its specific sequence of bases its helical nature and hydrogen bonding its deoxyribose sugar and phosphate groups its phosphodiester linkages and complementary strands its specific base pairing and hydrogen bonding
its specific base pairing and hydrogen bonding Correct. The hydrogen bonding makes it easy to separate the two strands. Specific complementary base pairing ensures that an accurate strand will be constructed on each template strand.
What are prions?
misfolded versions of normal protein that can cause disease
The rate of elongation in prokaryotes is _____ the rate in eukaryotes. ( Concept 16.2) much faster than The rates are not comparable, because elongation only occurs in prokaryotes. about the same speed as much slower than sometimes faster and sometimes slower than
much faster than Correct. The rate of elongation is about 500 nucleotides per second in bacteria and about 50 nucleotides per second in human cells.
To make a vaccine against mumps, measles, or rabies, which type of viruses would be useful?
negative-sense ssRNA viruses
In the figure, when new viruses are being assembled at the point marked IV, what mediates the assembly?
nothing; they self assemble
Which set of enzymes is involved in nucleotide excision repair? ( Concept 16.2) hydrolase, nuclease, and ligase DNA polymerase, helicase, primase nuclease, DNA polymerase, primase ligase, nuclease, and primase nuclease, DNA polymerase, and ligase
nuclease, DNA polymerase, and ligase Correct. Nucleotide excision repair involves nucleases, DNA polymerase, and ligase.
A base-pair substitution mutation in a germ cell line is likely to have no effect on phenotype if the substitution _____.
occurs in an intron
The two strands of a DNA double helix are antiparallel. This means that _____. ( Concept 16.2) the two strands are mirror images only one of the two strands can be used as a template for replication, because DNA polymerase only works in one direction one strand runs in the 5' to 3' direction, and the other runs in the 3' to 5' direction they both run in the 3' to 5' direction one strand is actually composed of RNA
one strand runs in the 5' to 3' direction, and the other runs in the 3' to 5' direction Correct. This allows the two strands to fit together properly.
Up until Hershey and Chase showed that DNA was the genetic molecule, what molecule was considered the best candidate for carrying genetic information and why? ( Concept 16.1) proteins because they were thought to be the only molecule with both the variety and specificity of function to account for the array of heritable traits observed carbohydrates because they are found in abundance in all organisms amino acids because of all the ways they can join together sterols because of the different variations on their ring structure nucleoside triphosphates because of the ability to add and remove phosphate groups
proteins because they were thought to be the only molecule with both the variety and specificity of function to account for the array of heritable traits observed Many scientists believed that proteins must be the chemical carriers of genetic information.
A virus consisting of a single strand of RNA, which is transcribed into complementary DNA, is a _______.
retrovirus
In his work with pneumonia-causing bacteria and mice, Griffith found that the polysaccharide coat of bacteria caused pneumonia. the protein coat from pathogenic cells was able to transform nonpathogenic cells. some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic. bacteriophages injected DNA into bacteria. heat-killed pathogenic cells caused pneumonia.
some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.
Which of the following could use reverse transcriptase to transcribe its genome?
ssRNA
A population of viruses with similar characteristics is called a _____.
strain
Bacteria can transcribe and translate human genes to produce functional human proteins because _____.
the genetic code is universal
In an important experiment, a radioactively labeled bacteriophage was allowed to infect bacteria. In a first trial, the phage contained radioactive DNA, and radioactivity was detected inside the bacteria. Next, phage containing radioactive protein was used, and the radioactivity was not detected inside the bacteria. These experiments led to the conclusion that _____. ( Concept 16.1) bacteriophages can infect bacteria genes are on chromosomes the genetic material of the phage is DNA the genetic material of the phage is protein DNA is made of nucleotides
the genetic material of the phage is DNA Correct. In order to replicate, viral material must enter a bacterial cell. This experiment showed that the viral DNA had entered the bacterial cell.
Which of the following statements describes the lysogenic cycle of lambda (λ) phage?
the phage genome replicates along with the host genome
A scientist assembles a bacteriophage with the protein coat of phage T2 and the DNA of phage T4. If this composite phage were allowed to infect a bacterium, the phages produced in the host cell would have _____. ( Concept 16.1) the protein and DNA of T4 a mixture of the DNA and proteins of both phages the protein of T4 and the DNA of T2 the protein and DNA of T2 the protein of T2 and the DNA of T4
the protein and DNA of T4 Correct. The protein and DNA would match that of the phage whose DNA was used.
Viruses _____.
use the host cell to copy themselves and make viral proteins
Put the following DNA-containing entities in order according to the amount of DNA found in their genomes. ( Concept 16.3) bacteria, virus, eukaryote eukaryote, virus, bacteria virus, bacteria, eukaryote bacteria, eukaryote, virus They all have about the same amount of DNA.
virus, bacteria, eukaryote Correct. In general, viruses have the smallest genomes, followed by bacteria, with eukaryotes having the largest genomes.
Avery and his colleagues' 1944 experiment showed that DNA _____. ( Concept 16.1) consists of sugars, phosphate groups, and bases uses three bases to code for one amino acid contains adenine, guanine, thymine, and cytosine was the substance that transformed the bacteria in Griffith's experiment has two strands held together with hydrogen bonds
was the substance that transformed the bacteria in Griffith's experiment Correct. Avery and his colleagues announced that the transforming agent was DNA.