front 1 Which of the following variations on translation would be most disadvantageous for a cell? | back 1 A) translating polypeptides directly from DNA |
front 2 Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because | back 2 A) metabolic enzymes require vitamin cofactors, and affected individuals have significant nutritional deficiencies. |
front 3 Garrod's information about the enzyme alteration resulting in alkaptonuria led to further elucidation of the same pathway in humans. Phenylketonuria (PKU) occurs when another enzyme in the pathway is altered or missing, resulting in a failure of phenylalanine (phe) to be metabolized to another amino acid: tyrosine. Tyrosine is an earlier substrate in the pathway altered in alkaptonuria. How might PKU affect the presence or absence of alkaptonuria? | back 3 B) It would have no effect, because tyrosine is also available from the diet. |
front 4 The nitrogenous base adenine is found in all members of which group? | back 4 C) ATP, RNA, and DNA |
front 5 A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is | back 5 A) 3' UCA 5'. |
front 6 The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following? | back 6 A) A gene from an organism can theoretically be expressed by any other organism. |
front 7 The "universal" genetic code is now known to have exceptions. Evidence for this can be found if which of the following is true? | back 7 A) If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only). |
front 8 Which of the following nucleotide triplets best represents a codon? | back 8 D) a triplet in the same reading frame as an upstream AUG |
front 9 Which of the following provides some evidence that RNA probably evolved before DNA? | back 9 D) DNA polymerase uses primer, usually made of RNA. |
front 10 Which of the following statements best describes the termination of transcription in prokaryotes? | back 10 B) RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript. |
front 11 Which of the following does not occur in prokaryotic eukaryotic gene expression, but does in eukaryotic gene expression? | back 11 C) A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end. |
front 12 RNA polymerase in a prokaryote is composed of several subunits. Most of these subunits are the same for the transcription of any gene, but one, known as sigma, varies considerably. Which of the following is the most probable advantage for the organism of such sigma switching? | back 12 B) It might allow the polymerase to recognize different promoters under certain environmental conditions. |
front 13 Which of the following is a function of a poly-A signal sequence? | back 13 B) It codes for a sequence in eukaryotic transcripts that signals enzymatic cleavage ~1035 nucleotides away. |
front 14 In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein? | back 14 C) RNA polymerase II |
front 15 Transcription in eukaryotes requires which of the following in addition to RNA polymerase? | back 15 D) several transcription factors (TFs) |
front 16 A part of the promoter, called the TATA box, is said to be highly conserved in evolution. Which of the following might this illustrate? | back 16 C) Any mutation in the sequence is selected against. |
front 17 The TATA sequence is found only several nucleotides away from the start site of transcription. This most probably relates to which of the following? | back 17 A) the number of hydrogen bonds between A and T in DNA |
front 18 What is a ribozyme? | back 18 B) an RNA with enzymatic activity |
front 19 A transcription unit that is 8,000 nucleotides long may use 1,200 nucleotides to make a protein consisting of approximately 400 amino acids. This is best explained by the fact that | back 19 A) many noncoding stretches of nucleotides are present in mRNA. |
front 20 During splicing, which molecular component of the spliceosome catalyzes the excision reaction? | back 20 C) RNA |
front 21 Alternative RNA splicing | back 21 B) can allow the production of proteins of different sizes from a single mRNA. |
front 22 In the structural organization of many eukaryotic genes, individual exons may be related to which of the following? | back 22 C) the various domains of the polypeptide product |
front 23 In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after he has removed its 5' cap and poly-A tail. Which of the following would you expect him to find? | back 23 D) The molecule is digested by exonucleases since it is no longer protected at the 5' end. |
front 24 Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the | back 24 E) bonding of the anticodon to the codon and the attachment of amino acids to tRNAs. |
front 25 What is the function of GTP in translation? | back 25 A) GTP energizes the formation of the initiation complex, using initiation factors. |
front 26 A mutant bacterial cell has a defective aminoacyl synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of the normal phenylalanine. The consequence of this for the cell will be that | back 26 B) proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU. |
front 27 There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that | back 27 B) the rules for base pairing between the third base of a codon and tRNA are flexible. |
front 28 Which of the following is the first event to take place in translation in eukaryotes? | back 28 E) the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA |
front 29 Which of the following is a function of a signal peptide? | back 29 D) to translocate polypeptides across the ER membrane |
front 30 When translating secretory or membrane proteins, ribosomes are directed to the ER membrane by | back 30 B) a signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane. |
front 31 An experimenter has altered the 3' end of the tRNA corresponding to the amino acid methionine in such a way as to remove the 3' AC. Which of the following hypotheses describes the most likely result? | back 31 C) The amino acid methionine will not bind. |
front 32 The process of translation, whether in prokaryotes or eukaryotes, requires tRNAs, amino acids, ribosomal subunits, and which of the following? | back 32 B) polypeptide factors plus GTP |
front 33 When the ribosome reaches a stop codon on the mRNA, no corresponding tRNA enters the A site. If the translation reaction were to be experimentally stopped at this point, which of the following would you be able to isolate? | back 33 A) an assembled ribosome with a polypeptide attached to the tRNA in the P site |
front 34 What is the function of the release factor (RF)? | back 34 B) It binds to the stop codon in the A site in place of a tRNA. |
front 35 When the function of the newly made polypeptide is to be secreted from the cell where it has been made, what must occur? | back 35 B) Its signal sequence must target it to the ER, from which it goes to the Golgi. |
front 36 Suppose that a mutation alters the formation of a tRNA such that it still attaches to the same amino acid (phe) but its anticodon loop has the sequence AAU that binds to the mRNA codon UUA (that usually specifies leucine leu). | back 36 C) One mutated tRNA molecule will be relatively inconsequential because it will compete with many "normal" ones. |
front 37 Why might a point mutation in DNA make a difference in the level of protein's activity? | back 37 D) It might substitute an amino acid in the active site. |
front 38 In the 1920s Muller discovered that X-rays caused mutation in Drosophila. In a related series of experiments in the 1940s, Charlotte Auerbach discovered that chemicals-she used nitrogen mustards-have a similar effect. A new chemical food additive is developed by a cereal manufacturer. Why do we test for its ability to induce mutation? | back 38 D) We want to prevent any increase in mutation frequency. |
front 39 Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product? | back 39 B) a deletion of two nucleotides |
front 40 What is the effect of a nonsense mutation in a gene? | back 40 C) It introduces a premature stop codon into the mRNA. |
front 41 A frameshift mutation could result from | back 41 E) either an insertion or a deletion of a base. |
front 42 Which of the following DNA mutations is the most likely to be damaging to the protein it specifies? | back 42 A) a base-pair deletion |
front 43 Which small-scale mutation would be most likely to have a catastrophic effect on the functioning of a protein? | back 43 B) a base deletion near the start of a gene |
front 44 The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in | back 44 D) a polypeptide missing an amino acid. |
front 45 Which of the following mutations is most likely to cause a phenotypic change? | back 45 D) a single nucleotide deletion in an exon coding for an active site |
front 46 If a protein is coded for by a single gene and this protein has six clearly defined domains, which number of exons below is the gene likely to have? | back 46 C) 8 |
front 47 Which of the following statements is true about protein synthesis in prokaryotes? | back 47 B) Translation can begin while transcription is still in progress. |
front 48 Of the following, which is the most current description of a gene? | back 48 C) a DNA sequence that is expressed to form a functional product: either RNA or polypeptide |
front 49 Gene expression in the domain Archaea in part resembles that of bacteria and in part that of the domain Eukarya. In which way is it most like the domain Eukarya? | back 49 A) Domain Archaea have numerous transcription factors. |
front 50 Which of the following is true of transcription in domain Archaea? | back 50 C) It is roughly simultaneous with translation. |
front 51 In comparing DNA replication with RNA transcription in the same cell, which of the following is true only of replication? | back 51 E) The entire template molecule is represented in the product. |
front 52 In order for a eukaryotic gene to be engineered into a bacterial colony to be expressed, what must be included in addition to the coding exons of the gene? | back 52 C) a bacterial promoter sequence |
front 53 When the genome of a particular species is said to include 20,000 protein-coding regions, what does this imply? | back 53 D) There are also genes for RNAs other than mRNA. |
front 54 In the transcription event of the previous DNA, where would the promoter be located? | back 54 B) to the right of the template strand |
front 55 What type of bonding is responsible for maintaining the shape of the tRNA molecule? | back 55 C) hydrogen bonding between base pairs |
front 56 In eukaryotic cells, transcription cannot begin until | back 56 B) several transcription factors have bound to the promoter. |
front 57 Which of the following is not true of a codon? | back 57 D) It extends from one end of a tRNA molecule. |
front 58 The anticodon of a particular tRNA molecule is | back 58 A) complementary to the corresponding mRNA codon. |
front 59 Which of the following is not true of RNA processing? | back 59 A) Exons are cut out before mRNA leaves the nucleus. |
front 60 Which component is not directly involved in translation? E) GTP | back 60 B) DNA |
front 61 Which of the following mutations would be most likely to have a harmful effect on an organism? | back 61 E) a single nucleotide insertion downstream of, and close to, the start of the coding sequence |