Where does RNA polymerase begin transcribing a gene into mRNA?
-Transfer RNA acts to translate the message to RNA polymerase.
-It looks for the AUG start codon.
-It starts after a certain nucleotide sequence called a promoter.
-The ribosome directs it to the correct portion of the -DNA molecule.
-It starts at one end of the chromosome.
answer
It starts after a certain nucleotide sequence called a promoter.
(In both eukaryotes and prokaryotes, RNA polymerase binds to the gene's promoter and begins transcription at a nucleotide known as the start point, although in eukaryotes the binding of RNA polymerase to the promoter requires transcription factors.)
question
Which of the following molecules are produced by transcription?
Select all that apply.
-Ribozymes
-Messenger RNA
-Ribosomal proteins
answer
-Ribozymes
-Messenger RNA
question
Which of the following molecules is/are produced by translation? Include molecules that are subject to further modification after initial synthesis.
Select all that apply.
-Aminoacyl-tRNA synthetase
-The amino acid glycine
-RNA polymerase
answer
-Aminoacyl-tRNA synthetase
-RNA polymerase
question
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?
-Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that are not translated.
-Each amino acid in a protein is encoded by a triplet of nucleotides.
-Many genes are subject to alternative RNA splicing.
answer
-Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that are not translated.
question
What name is given to the process in which a strand of DNA is used as a template for the manufacture of a strand of pre-mRNA?
-RNA processing
-gene expression
-polypeptide formation
-transcription
-translation
answer
-transcription
(Transcription is the process by which a DNA template is used for the manufacture of several different types of RNA)
question
What name is given to the process in which the information encoded in a strand of mRNA is used to construct a protein?
-RNA processing
-gene expression
-polypeptide formation
-transcription
-translation
answer
-translation
(Translation is the process by which information encoded in RNA is used to manufacture a polypeptide.)
question
What name is given to the process in which pre-mRNA is edited into mRNA?
-RNA processing
-gene expression
-polypeptide formation
-transcription
-translation
answer
-RNA processing
(RNA processing edits the RNA transcript that has been assembled along a DNA template.)
question
Polypeptides are assembled from _____.
-hexoses
-glycerol
-nucleotides
-proteins
-amino acids
answer
-amino acids
(Proteins are composed of amino acid monomers)
question
RNA processing converts the RNA transcript into _____.
-a protein
-DNA
-a eukaryotic cell
-mRNA
-a polypeptide
answer
-mRNA
(The editing of the RNA transcript produces mRNA)
question
Where does translation take place?
-Golgi apparatus
-Ribosome
-Nucleus
-Endoplasmic reticulum
answer
-Ribosome
(Translation, or protein synthesis, occurs at the ribosome)
question
Which nucleic acid is translated to make a protein?
-tRNA
-rRNA
-DNA
-mRNA
answer
-mRNA
(mRNA is the message that is translated to make a protein)
question
Which of the following processes is an example of a post-translational modification?
-Elongation
-Peptide bond formation
-Initiation
-Phosphorylation
answer
-Phosphorylation
(Enzymes can phosphorylate proteins to alter their activity.)
question
Which of the following steps occurs last in the initiation phase of translation?
-A peptide bond is formed between two adjacent amino acids.
-An aminoacyl tRNA binds to the start codon.
-The large ribosomal subunit joins the complex.
-The small subunit of the ribosome binds to the 5' cap on the mRNA.
answer
-The large ribosomal subunit joins the complex
(This step occurs after the 5' mRNA is bound by the ribosome and the start codon is bound by an aminoacyl tRNA.)
question
At which site do new aminoacyl tRNAs enter the ribosome during elongation?
-P-site
-B-site
-A-site
-E-site
answer
A-site
(This is the site at which new aminoacyl tRNAs that are complementary to the mRNA codon enter the ribosome.)
question
What is meant by translocation?
-The completed polypeptide is released from the ribosome.
-The two ribosomal subunits are joined in a complex.
-The ribosome slides one codon down the mRNA.
-The polypeptide chain grows by one amino acid.
answer
-The ribosome slides one codon down the mRNA.
(Translocation is the process by which the ribosome slides down the mRNA so a new cycle of elongation can begin.)
question
True or false. A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated.
-True
-False
answer
-False
(There are no tRNAs complementary to the three stop codons; termination occurs when release factors recognize the stop codon in the A-site and catalyze the release of the polypeptide from the tRNA in the P-site.)
question
What enzyme catalyzes the attachment of an amino acid to tRNA?
-aminoacyl-tRNA synthetase
-rubisco
-dextrinase
-argininosuccinate lyase
-nuclease
answer
-aminoacyl-tRNA synthetase
(This enzyme matches a particular tRNA with a particular amino acid)
question
The tRNA anticodon, GAC, is complementary to the mRNA codon with the sequence _____.
-CAG
-CTG
-GAC
-CUG
-TCG
answer
-CUG
(In RNA uracil replaces thymine.)
question
The initiator tRNA attaches at the ribosome's _____ site.
-A
-translocation
-E
-P
-Q
answer
-P
(The initiator tRNA attaches to the ribosome's P site.)
question
During RNA processing a(n) _____ is added to the 5' end of the RNA.
-3' untranslated region
-a long string of adenine nucleotides
-5' untranslated region
-coding segment
-modified guanine nucleotide
answer
-modified guanine nucleotide
(The 5' cap consists of a modified guanine nucleotide.)
question
During RNA processing a(n) _____ is added to the 3' end of the RNA.
-3' untranslated region
-a long string of adenine nucleotides
-5' untranslated region
-coding segment
-modified guanine nucleotide
answer
-a long string of adenine nucleotides
(A poly-A tail is added to the 3' end of the RNA.)
question
Spliceosomes are composed of _____.
-small RNAs and proteins
-polymerases and ligases
-introns and exons
-the RNA transcript and protein
answer
-small RNAs and proteins
(Spliceosomes are complexes composed of small RNAs and proteins.)
question
The RNA segments joined to one another by spliceosomes are _____.
-caps
-exons
-snRNPs
-tails
-introns
answer
-exons
(Exons are expressed regions)
question
Translation occurs in the _____.
-cytoplasm
-lysosome
-nucleus
-Golgi apparatus
-nucleoplasm
answer
-cytoplasm
(Ribosomes, the sites of translation, are found in the cytoplasm)
question
What is the process called that converts the genetic information stored in DNA to an RNA copy?
-Transcription
-Replication
-Translation
-Translocation
answer
-transcription
(DNA is transcribed to give an RNA copy.)
question
DNA does not store the information to synthesize which of the following?
-Organelles
-DNA
-Messenger RNA
-Proteins
answer
-organelles
(Synthesis of organelles is not directly coded in the DNA.)
question
Transcription begins at a promoter. What is a promoter?
-The same as a start codon
-A site found on the RNA polymerase
-A site in DNA that recruits the RNA Polymerase
-Part of the RNA molecule itself
answer
-A site in DNA that recruits the RNA Polymerase
(This is the site where the RNA polymerase must bind to initiate transcription.)
question
Which of the following statements best describes the promoter of a protein-coding gene?
-The promoter is a site at which only RNA polymerase will bind.
-The promoter is a site found on RNA polymerase.
-The promoter is a nontranscribed region of a gene.
-The promoter is part of the RNA molecule itself.
answer
-The promoter is a nontranscribed region of a gene.
(The promoter is the regulatory region of a protein-coding gene at which RNA polymerase must bind to initiate transcription—it is not transcribed into the RNA.)
question
What determines which base is to be added to an RNA strand during transcription?
-The previous base
-The order of the chemical groups in the backbone of the RNA molecule
-Base pairing between the DNA template strand and the RNA nucleotides
-Base pairing between the two DNA strands
answer
-Base pairing between the DNA template strand and the RNA nucleotides
(Transcription involves the formation of an RNA strand that is complementary to the DNA template strand.)
question
Which of the following terms best describes the relationship between the newly synthesized RNA molecule and the DNA template strand?
-Covalently bound
-Complementary
-Permanently base-paired
-Identical
answer
-Complementary
(Because the template strand determines the nucleotides to be added to the RNA strand, using the same complementarity rules of the DNA, they will be complementary to each other.)
question
What happens to RNA polymerase II after it has completed transcription of a gene?
-It is degraded.
-It begins transcribing the next gene on the chromosome.
-It joins with another RNA polymerase to carry out transcription.
-It is free to bind to another promoter and begin transcription.
answer
-It is free to bind to another promoter and begin transcription.
(The enzyme is free to transcribe other genes in the cell.)
question
A codon consists of __________ bases and specifies which __________ will be inserted into the polypeptide chain.
-three ... nucleotide
-four ... amino acid
-four ... fatty acid
-three ... amino acid
-two ... nucleotide
answer
-three...amino acid
(Three nucleotide bases make up a codon and specify which amino acid comes next in the sequence.)
question
The flow of information in a cell proceeds in what sequence?
-from DNA to protein to RNA
-from RNA to protein to DNA
-from protein to RNA to DNA
-from DNA to RNA to protein
-from RNA to DNA to protein
answer
-from DNA to RNA to protein
(In a cell, inherited information flows from DNA to RNA to protein.)
question
Which of these correctly illustrates the pairing of DNA and RNA nucleotides?
GTTACG
CAATCG
GTTACG
CAAUGC
GTTACG
GTTACG
GTTACG
ACCGTA
GTTACG
UAACAU
answer
GTTACG
CAAUGC
(In RNA, uracil takes the place of thymine.)
question
The direction of synthesis of an RNA transcript is _____.
-1' —> 5'
-5' —> 3'
-1' —> 3'
-3' —> 5'
-2' —> 4'
answer
-5' —> 3'
(Nucleotides are added to the 3' end of RNA.)
question
What is the function of RNA polymerase?
-It proceeds slowly along the DNA strand, requiring about a minute to add two nucleotides to the growing mRNA molecule.
-It unwinds the double helix and adds nucleotides to a growing strand of RNA.
-It adds nucleotides to the 5' end of the growing mRNA molecule.
-It relies on other enzymes to unwind the double helix.
-All of the listed responses are correct.
answer
-It unwinds the double helix and adds nucleotides to a growing strand of RNA.
(RNA polymerase has several functions in transcription, including unwinding the DNA double helix and adding RNA nucleotides.)
question
What is a ribozyme?
-an enzyme that holds open the DNA double helix while RNA polymerase adds nucleotides
-a DNA sequence near the promoter that assists in the binding of RNA polymerase
-a biological catalyst made of RNA
-a biological catalyst consisting of DNA
-a mutated ribosome
answer
-a biological catalyst made of RNA
(A number of examples of biological catalysts containing RNA have been discovered, including ribozymes, snRNAs, and ribosomes themselves.)
question
True or false? A codon is a group of three bases that can specify more than one amino acid.
-True
-False
answer
-False
(A codon is a group of three bases that can specify only one amino acid.)
question
Which of the following statements about mutations is false?
-A knock-out mutation results in a total absence of the mutated protein.
-Addition and deletion mutations disrupt the primary structure of proteins.
-An addition mutation results in an added base in the -DNA sequence.
-A deletion mutation results in the loss of a base in the DNA sequence.
answer
-A knock-out mutation results in a total absence of the mutated protein.
(A knock-out mutation refers to the loss of a protein's function but not necessarily to its complete absence.)
question
If a DNA sequence is altered from TAGCTGA to TAGTGA, what kind of mutation has occurred?
-Addition.
-None.
-Deletion.
-Both addition and deletion.
answer
-Deletion
(The original sequence has lost the base C.)
question
Which mutation(s) would not change the remainder of the reading frame of a gene sequence that follows the mutation(s)?
-One addition mutation.
-One addition and one deletion mutation.
-One deletion mutation.
-One addition and two deletion mutations.
answer
-One addition and one deletion mutation
(This combination results in no net change in the number of bases, so the reading frame would eventually be restored.)
question
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?
-Three.
-Two.
-None.
-One.
answer
-Two
(The second and third codons in the new sequence are different from the original codons.)
question
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?
-An addition mutation and a deletion mutation.
-An addition mutation
-None.
-A deletion mutation.
answer
-An addition mutation and a deletion mutation.
(If the mutations occur within the same codon, only that codon (amino acid) will be altered.)
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