AP Bio: Chapter 14
Which of the following is NOT true of a codon? 1. It never codes for more than one amino acid. 2. It consists of three nucleotides. 3. It is the basic unit of the genetic code. 4. It extends from one end of a tRNA molecule. 5. It may code for the same amino acid as another codon.
It extends from one end of a tRNA molecule.
What is the effect of a nonsense mutation in a gene? 1. It prevents introns from being excised. 2. It alters the reading frame of the mRNA. 3. It introduces a premature stop codon into the mRNA. 4. It has no effect on the amino acid sequence of the encoded protein. 5. It changes an amino acid in the encoded protein.
It introduces a premature stop codon into the mRNA.
Where does RNA polymerase begin transcribing a gene into mRNA? 1. It starts at one end of the chromosome. 2. Transfer RNA acts to translate the message to RNA polymerase. 3. The ribosome directs it to the correct portion of the DNA molecule. 4. It starts after a certain nucleotide sequence called a promoter. 5. It looks for the AUG start codon.
It starts after a certain nucleotide sequence called a promoter.
What is the function of RNA polymerase? 1. It proceeds slowly along the DNA strand, requiring about a minute to add two nucleotides to the growing mRNA molecule. 2. It unwinds the double helix and adds nucleotides to a growing strand of RNA. 3. It adds nucleotides to the 5' end of the growing mRNA molecule. 4. It relies on other enzymes to unwind the double helix. 5. All of the above.
It unwinds the double helix and adds nucleotides to a growing strand of RNA.
A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is 1) 3' UGA 5'. 2) 5' TCA 3'. 3) 3' UCA 5'. 4) 3' ACU 5'. 5) either UCA or TCA, depending on wobble in the first base.
3' UCA 5'.
RNA polymerase moves in which direction along the DNA? •5' to 3' along whichever strand it's on •5' to 3' along the template strand •3' to 5' along the nontemplate strand •5' to 3' along the double-stranded DNA •3' to 5' along the template strand
3' to 5' along the template strand
Use the following model of a eukaryotic transcript to answer the next few questions. 5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' Which components of the previous molecule will also be found in mRNA in the cytosol? •5' E1 I1 E2 I2 E3 I3 E4 3' •5' I1 I2 I3 3' •5' UTR I1 I2 I3 UTR 3' •5' UTR E1 E2 E3 E4 UTR 3' •5' E1 E2 E3 E4 3'
5' UTR E1 E2 E3 E4 UTR 3'
The direction of synthesis of an RNA transcript is _____. 1' —> 5' 5' —> 3' 1' —> 3' 3' —> 5' 2' —> 4'
5' —> 3'
Which of the following statements about mutations is false? 1. An addition mutation results in an added base in the DNA sequence. 2. A deletion mutation results in the loss of a base in the DNA sequence. 3. Addition and deletion mutations disrupt the primary structure of proteins. 4. A knock-out mutation results in a total absence of the mutated protein.
A knock-out mutation results in a total absence of the mutated protein.
Transcription begins at a promoter. What is a promoter? 1. The same as a start codon 2. A site in DNA that recruits the RNA Polymerase 3. Part of the RNA molecule itself 4. A site found on the RNA polymerase
A site in DNA that recruits the RNA Polymerase
At which site do new aminoacyl tRNAs enter the ribosome during elongation? •A-site •E-site •B-site •P-site
A-site
A part of the promoter, called the TATA box, is said to be highly conserved in evolution. Which of the following might this illustrate? 1. Any mutation in the sequence is selected against. 2. The sequence evolves very rapidly. 3. The sequence is transcribed at the start of every gene. 4. The sequence does not mutate. 5. The sequence is found in many but not all promoters.
Any mutation in the sequence is selected against.
If a DNA sequence is altered from TAGCTGA to TAGTGA, what kind of mutation has occurred? 1. Both addition and deletion. 2. None. 3. Addition. 4. Deletion
Deletion
Which of the following mutations would likely be most dangerous to a cell? 1. Deletion of one nucleotide 2. Deletion of three nucleotides 3. Substitution of one nucleotide for another
Deletion of one nucleotide
Use the following information to answer the next few questions. A transfer RNA (#1) attached to the amino acid lysine enters the ribosome. The lysine binds to the growing polypeptide on the other tRNA (#2) already in the ribosome. Where does tRNA #2 move to after this bonding of lysine to the polypeptide? 1. E site 2. A site 3. exit tunnel 4. directly to the cytosol 5. P site
E site
Which one of the following is true of tRNAs? Each tRNA binds a particular amino acid. tRNAs carry special sequences known as codons. There are four types of tRNA. tRNAs are double-stranded. All of the above.
Each tRNA binds a particular amino acid.
Which of the following is NOT true of RNA processing? 1. Nucleotides may be added at both ends of the RNA. 2. Exons are cut out before mRNA leaves the nucleus. 3. Ribozymes may function in RNA splicing. 4. A primary transcript is often much longer than the final RNA molecule that leaves the nucleus. 5. RNA splicing can be catalyzed by spliceosomes.
Exons are cut out before mRNA leaves the nucleus.
True or false. A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated. True False
False
True or false? A codon is a group of three bases that can specify more than one amino acid. True False
False
The "universal" genetic code is now known to have exceptions. Evidence for this can be found if which of the following is true? 1. If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only). 2. If one stop codon, such as UGA, is found to have a different effect on translation than another stop codon, such as UAA. 3. If several codons are found to translate to the same amino acid, such as serine. 4. If a single mRNA molecule is found to translate to more than one polypeptide when there are two or more AUG sites. 5. If prokaryotic organisms are able to translate a eukaryotic mRNA and produce the same polypeptide.
If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only).
Which mutation(s) would not change the remainder of the reading frame of a gene sequence that follows the mutation(s)? 1. One deletion mutation. 2. One addition and two deletion mutations. 3. One addition and one deletion mutation. 4. One addition mutation.
One addition and one deletion mutation.
Suppose that an error in transcription alters the formation of a single tRNA molecule in a cell. The altered tRNA still attaches to the same amino acid (Phe), but its anticodon loop has the sequence AAU, which binds to the mRNA codon UUA (usually specifying leucine, Leu). What will be the effect on translation in this cell? 1. The altered tRNA will result in an amino acid variant in all copies of the protein. 2. One altered tRNA molecule will be relatively inconsequential because it will compete with many "normal" ones. 3. The altered tRNA will be so unstable that it will not participate in translation. 4. The altered tRNA will cause this mRNA to make only nonfunctioning product. 5. The tRNA-Leu will not be able to enter the ribosome to bind to the UUA codon.
One altered tRNA molecule will be relatively inconsequential because it will compete
DNA does not store the information to synthesize which of the following? 1. Organelles 2. Messenger RNA 3. DNA 4. Proteins
Organelles
What is the process called that converts the genetic information stored in DNA to an RNA copy? 1. Replication 2. Transcription 3. Translation 4. Translocation
Transcription
Which of the following statements is true about protein synthesis in prokaryotes? 1. Extensive RNA processing is required before prokaryotic transcripts can be translated. 2. Translation requires antibiotic activity. 3. Translation can begin while transcription is still in progress. 4. Unlike eukaryotes, prokaryotes require no initiation or elongation factors. 5. Prokaryotic cells have complicated mechanisms for targeting proteins to the appropriate cellular organelles.
Translation can begin while transcription is still in progress.
If the sequence ATGCATGTCAATTGA were mutated such that a base were inserted after the first G and the third T were deleted, how many amino acids would be changed in the mutant protein? 1. Three. 2. None. 3. Two. 4. One.
Two
During RNA processing a(n) _____ is added to the 3' end of the RNA. 1) 3' untranslated region 2) a long string of adenine nucleotides 3) 5' untranslated region 4) coding segment 5) modified guanine nucleotide
a long string of adenine nucleotides
The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in 1. a nucleotide mismatch. 2. a nonsense mutation. 3. a polypeptide missing an amino acid. 4. a frameshift mutation. 5. a base-pair substitution.
a polypeptide missing an amino acid.
When translating secretory or membrane proteins, ribosomes are directed to the ER membrane by 1. a signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane. 2. a signal sequence of RNA that precedes the start codon of the message. 3. a specific characteristic of the ribosome itself, which distinguishes free ribosomes from bound ribosomes. 4. moving through a specialized channel of the nucleus. 5. a chemical signal given off by the ER.
a signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane.
Which of the following mutations would be most likely to have a harmful effect on an organism? 1. a nucleotide-pair substitution 2. a single nucleotide deletion in the middle of an intron 3. a single nucleotide deletion near the end of the coding sequence 4. a single nucleotide insertion downstream of, and close to, the start of the coding sequence 5. a deletion of three nucleotides near the middle of a gene
a single nucleotide insertion downstream of, and close to, the start of the coding sequence
Polypeptides are assembled from _____. hexoses glycerol nucleotides proteins amino acids
amino acids
What enzyme catalyzes the attachment of an amino acid to tRNA? 1. aminoacyl-tRNA synthetase 2. rubisco 3. dextrinase 4. argininosuccinate lyase 5. nuclease
aminoacyl-tRNA synthetase
#2 What is a ribozyme? 1. an enzyme that synthesizes RNA as part of the transcription process 2. an enzyme that catalyzes the association between the large and small ribosomal subunits 3. an enzyme that uses RNA as a substrate 4. an RNA with enzymatic activity 5. an enzyme that synthesizes RNA primers during DNA replication
an RNA with enzymatic activity
Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the 1. attachment of amino acids to tRNAs. 2. bonding of the anticodon to the codon and the attachment of amino acids to tRNAs. 3. shape of the A and P sites of ribosomes. 4. bonding of the anticodon to the codon. 5. binding of ribosomes to mRNA.
bonding of the anticodon to the codon and the attachment of amino acids to tRNAs.
The anticodon of a particular tRNA molecule is __________. 1. changeable, depending on the amino acid that attaches to the tRNA 2. complementary to the corresponding triplet in rRNA 3. the part of tRNA that bonds to a specific amino acid 4. complementary to the corresponding mRNA codon 5. catalytic, making the tRNA a ribozyme
complementary to the corresponding mRNA codon
Translation occurs in the _____. 1. cytoplasm 2. lysosome 3. nucleus 4. Golgi apparatus 5. nucleoplasm
cytoplasm
The RNA segments joined to one another by spliceosomes are _____. 1. caps 2. exons 3. snRNPs 4. tails 5. introns
exons
The flow of information in a cell proceeds in what sequence? 1. from RNA to DNA to protein 2. from DNA to protein to RNA 3. from DNA to RNA to protein 4. from RNA to protein to DNA 5. from protein to RNA to DNA
from DNA to RNA to protein
The initiator tRNA attaches at the ribosome's _____ site. •A •translocation •E •P •Q
P
Which of the following processes is an example of a post-translational modification? 1. Elongation 2. Peptide bond formation 3. Phosphorylation 4. Initiation
Phosphorylation
Which of the following molecules is/are produced by translation? Include molecules that are subject to further modification after initial synthesis. 1. The amino acid glycine 2. RNA polymerase 3. Aminoacyl-tRNA synthetase
RNA polymerase AND Aminoacyl-tRNA synthetase
Where does translation take place? 1. Nucleus 2. Ribosome 3. Endoplasmic reticulum 4. Golgi apparatus
Ribosome
In comparing DNA replication with RNA transcription in the same cell, which of the following is true only of replication? 1. The entire template molecule is represented in the product. 2. It uses RNA polymerase. 3. The process is extremely fast once it is initiated. 4. It makes a new molecule from its 5' end to its 3' end. 5. The process occurs in the nucleus of a eukaryotic cell.
The entire template molecule is represented in the product.
Which of the following steps occurs last in the initiation phase of translation? 1. The small subunit of the ribosome binds to the 5' cap on the mRNA. 2. An aminoacyl tRNA binds to the start codon. 3. A peptide bond is formed between two adjacent amino acids. 4. The large ribosomal subunit joins the complex.
The large ribosomal subunit joins the complex.
Transcription in eukaryotes requires which of the following in addition to RNA polymerase? 1. ribosomes and tRNA 2. aminoacyl-tRNA synthetase 3. several transcription factors 4. start and stop codons 5. the protein product of the promoter
several transcription factors
In eukaryotic cells, transcription cannot begin until __________. 1. The 5' caps are removed from the mRNA 2. the DNA introns are removed from the template 3. DNA nucleases have isolated the transcription unit 4. the two DNA strands have completely separated and exposed the promoter 5. several transcription factors have bound to the promoter
several transcription factors have bound to the promoter
Spliceosomes are composed of _____. 1. snRNPs and other proteins 2. polymerases and ligases 3. introns and exons 4. the RNA transcript and protein 5. snRNPs and snurps
snRNPs and other proteins
After an RNA molecule is transcribed from a eukaryotic gene, what are removed and what are spliced together to produce an mRNA molecule with a continuous coding sequence? 1. exons ... introns 2. silencers ... enhancers 3. promoters ... operators 4. operators ... promoters 5. introns ... exons
introns ... exons
RNA processing converts the RNA transcript into _____. a protein DNA a eukaryotic cell mRNA a polypeptide
mRNA
Which nucleic acid is translated to make a protein? 1. mRNA 2. DNA 3. tRNA 4. rRNA
mRNA
There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that 1. the DNA codes for all 61 tRNAs but some are then destroyed. 2. some tRNAs have anticodons that recognize four or more different codons. 3. the rules for base pairing between the third base of a codon and tRNA are flexible. 4. competitive exclusion forces some tRNAs to be destroyed by nucleases. 5. many codons are never used, so the tRNAs that recognize them are dispensable.
the rules for base pairing between the third base of a codon and tRNA are flexible.
Which of the following is the first event to take place in translation in eukaryotes? 1. the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA 2. binding of the larger ribosomal subunit to smaller ribosomal subunits 3. base pairing of activated methionine-tRNA to AUG of the messenger RNA 4. elongation of the polypeptide 5. covalent bonding between the first two amino acids
the small subunit of the ribosome recognizes and attaches to the 5' cap of mRNA
A codon consists of _____ bases and specifies which _____ will be inserted into the polypeptide chain. 1. three ... amino acid 2. four ... amino acid 3. four ... fatty acid 4. three ... nucleotide 5. two ... nucleotide
three ... amino acid
How is translation initiated? 1. The small ribosomal subunit binds to the mRNA. 2. The tRNA bearing methionine binds to the start codon. 3. The large ribosomal subunit binds to the small one. 4. The start codon signals the start of translation. 5. All of the above.
All of the above.
If a mutated DNA sequence produces a protein that differs in one central amino acid from the normal protein, which of the following kinds of mutations could have occurred? 1. A deletion mutation. 2. An addition mutation and a deletion mutation. 3. An addition mutation 4. None.
An addition mutation and a deletion mutation.
What determines which base is to be added to an RNA strand during transcription? 1. The order of the chemical groups in the backbone of the RNA molecule 2. Base pairing between the two DNA strands 3. Base pairing between the DNA template strand and the RNA nucleotides 4. The previous base
Base pairing between the DNA template strand and the RNA nucleotides
The tRNA anticodon, GAC, is complementary to the mRNA codon with the sequence _____. •CAG •CTG •GAC •CUG •TCG
CUG
Which of the following terms best describes the relationship between the newly synthesized RNA molecule and the DNA template strand? 1. Covalently bound 2. Complementary 3. Identical 4. Permanently base-paired
Complementary
Which component is NOT directly involved in translation? 1. tRNA 2. mRNA 3. DNA 4. GTP 5. ribosomes
DNA
What is the function of the release factor (RF)? 1. It supplies a source of energy for termination of translation. 2. It binds to the stop codon in the A site in place of a tRNA. 3. It separates tRNA in the A site from the growing polypeptide. 4. It releases the ribosome from the ER to allow polypeptides into the cytosol. 5. It releases the amino acid from its tRNA to allow the amino acid to form a peptide bond
It binds to the stop codon in the A site in place of a tRNA.
What happens to RNA polymerase II after it has completed transcription of a gene? 1. It joins with another RNA polymerase to carry out transcription. 2. It is free to bind to another promoter and begin transcription. 3. It begins transcribing the next gene on the chromosome. 4. It is degraded.
It is free to bind to another promoter and begin transcription.
Which of the following best describes the significance of the TATA box in eukaryotic promoters? 1. It is the recognition site for a specific transcription factor. 2. It prevents supercoiling of the DNA near the start site. 3. It is the recognition site for ribosomal binding. 4. It sets the reading frame of the mRNA. 5. Its significance has not yet been determined.
It is the recognition site for a specific transcription factor.
Why might a point mutation in DNA make a difference in the level of a protein's activity? 1. It might exchange one serine codon for a different serine codon. 2. It might substitute a different amino acid in the active site. 3. It might exchange one stop codon for another stop codon. 4. It might result in a chromosomal translocation. 5. It might substitute the N-terminus of the polypeptide for the C-terminus.
It might substitute a different amino acid in the active site.
The average length of a transcription unit along a eukaryotic DNA molecule is about 27,000 nucleotide pairs, whereas an averaged-sized protein is about 400 amino acids long. What is the best explanation for this fact? 1. Each amino acid in a protein is encoded by a triplet of nucleotides. 2. Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that are not translated. 3. Many genes are subject to alternative RNA splicing.
Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that are not translated.
Which of the following statements best describes the promoter of a protein-coding gene? 1. The promoter is part of the RNA molecule itself. 2. The promoter is a site at which only RNA 3. polymerase will bind. 4. The promoter is a site found on RNA polymerase. 5. The promoter is a nontranscribed region of a gene.
The promoter is a nontranscribed region of a gene
What is meant by translocation? 1. The ribosome slides one codon down the mRNA. 2. The completed polypeptide is released from the ribosome. 3. The polypeptide chain grows by one amino acid. 4. The two ribosomal subunits are joined in a complex.
The ribosome slides one codon down the mRNA.
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? 1. We worry about its ability to cause infection. 2. We want to prevent any increase in mutation frequency. 3. We want to be sure that it increases the rate of mutation sufficiently. 4. We want to make sure that it does not emit radiation. 5. We worry that it might cause mutation in cereal grain plants.
We want to prevent any increase in mutation frequency.
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? 1. eukaryotic polymerases 2. eukaryotic tRNAs 3. the introns 4. eukaryotic ribosomal subunits 5. a bacterial promoter sequence
a bacterial promoter sequence
Which of the following DNA mutations is the most likely to be damaging to the protein it specifies? 1. a codon deletion 2. a base-pair deletion 3. a codon substitution 4. a point mutation 5. a substitution in the last base of a codon
a base-pair deletion
#1 What is a ribozyme? 1. a DNA sequence near the promoter that assists in the binding of RNA polymerase 2. an enzyme that holds open the DNA double helix while RNA polymerase adds nucleotides 3. a biological catalyst consisting of DNA 4. a mutated ribosome 5. a biological catalyst made of RNA
a biological catalyst made of RNA
A eukaryotic 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 1. there is redundancy and ambiguity in the genetic code. 2. many noncoding stretches of nucleotides are present in eukaryotic DNA. 3. there are termination exons near the beginning of mRNA. 4. nucleotides break off and are lost during the transcription process. 5. many nucleotides are needed to code for each amino acid.
many noncoding stretches of nucleotides are present in eukaryotic DNA.
During RNA processing a(n) _____ is added to the 5' end of the RNA. 1) 3' untranslated region 2) a long string of adenine nucleotides 3) 5' untranslated region 4) coding segment 5) modified guanine nucleotide
modified guanine nucleotide
A mutant bacterial cell has a defective aminoacyl-tRNA 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 1. none of the options will occur; the cell will recognize the error and destroy the tRNA. 2. none of the proteins in the cell will contain phenylalanine. 3. proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU. 4. the cell will compensate for the defect by attaching phenylalanine to tRNAs with lysine-specifying anticodons. 5. the ribosome will skip a codon every time a UUU is encountered.
proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.
Which of the following experimental procedures is most likely to hasten mRNA degradation in a eukaryotic cell? 1. removal of one or more exons 2. methylation of histones 3. methylation of C nucleotides 4. enzymatic lengthening of the poly-A tail 5. removal of the 5' cap
removal of the 5' cap
