BIOLOGY CH. 17 Gene Expression: From Gene to Protein
What name is given to the process in which pre-mRNA is edited into mRNA? RNA processing gene expression polypeptide formation transcription translation
A. RNA processing RNA processing edits the RNA transcript that has been assembled along a DNA template
Which of the following molecules is/are produced by translation? Include molecules that are subject to further modification after initial synthesis.
Aminoacyl-tRNA synthetase RNA polymerase RNA polymerase and aminoacyl-tRNA synthetase, like other proteins, are produced by translation of mRNA, when amino acids such as glycine are linked to form polypeptides. Read about translation.
Which of the following steps occurs last in the initiation phase of translation? The small subunit of the ribosome binds to the 5' cap on the mRNA. An aminoacyl tRNA binds to the start codon. A peptide bond is formed between two adjacent amino acids. The large ribosomal subunit joins the complex.
D. 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.
What happens to RNA polymerase II after it has completed transcription of a gene?
It is free to bind to another promoter and begin transcription. The enzyme is free to transcribe other genes in the cell.
RNA polymerase
RNA polymerase untwists a portion of the DNA double helix.
Refer to the figure. Which of the triplets below is a possible anticodon for a tRNA that transports proline to a ribosome?
3-GGC-5
A particular triplet of bases in the template strand of DNA is 5-AGT-3. What would be the corresponding codon for the mRNA that is transcribed?
3-UCA-5
The direction of synthesis of an RNA transcript is _____.
5' —> 3' Nucleotides are added to the 3' end of RNA
Which of the following statements about mutations is false? A knock-out mutation results in a total absence of the mutated protein. A deletion mutation results in the loss of a base in the DNA sequence. Addition and deletion mutations disrupt the primary structure of proteins. An addition mutation results in an added base in the DNA sequence.
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.
During the elongation phase of translation, which site in the ribosome represents the location where a codon is being read?
A site
Transcription begins at a promoter. What is a promoter?
A site in DNA that recruits the RNA Polymerase. This is the site where the RNA polymerase must bind to initiate transcription.
Which of the following processes occurs when termination of translation takes place?
A stop codon is reached.
Which one of the following is true of tRNAs? There are four types of tRNA. Each tRNA binds a particular codon. tRNAs carry special sequences known as codons. tRNAs are double-stranded. All of the listed answers are correct. None of the listed answers is correct
The correct response is not listed in the choices. The tRNA transfers an amino acid to the growing polypeptide chain. It is a molecule involved in translation of mRNA.
During RNA processing a(n) _____ is added to the 3' end of the RNA.
a long string of adenine nucleotides A poly-A tail is added to the 3' end of the RNA.
Translation occurs in the _____.
cytoplasm Ribosomes, the sites of translation, are found in the cytoplasm.
The RNA segments joined to one another by spliceosomes are _____.
exons Exons are expressed regions
What type of bonding is responsible for maintaining the shape of the tRNA molecule shown in the figure?
hydrogen bonding between base pairs
RNA processing converts the RNA transcript into _____. a protein DNA a eukaryotic cell mRNA a polypeptide
mRNA The editing of the RNA transcript produces mRNA.
Which nucleic acid is translated to make a protein?
mRNA mRNA is the message that is translated to make a protein.
Transcription in eukaryotes requires which of the following molecules in addition to RNA polymerase?
several transcription factors
In the structural organization of many eukaryotic genes, individual exons may be related to which of the following?
the various domains of the polypeptide product
At which site do new aminoacyl tRNAs enter the ribosome during elongation? B-site E-site P-site A-site
A-site This is the site at which new aminoacyl tRNAs that are complementary to the mRNA codon enter the ribosome.
What determines which base is to be added to an RNA strand during transcription?
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.
Which of the following processes occurs in eukaryotic gene expression? mRNA, tRNA, and rRNA are translated. RNA polymerase binds to the terminator sequence. RNA polymerase requires tRNA to elongate the molecule. A cap is added to the 5 end of the mRNA.
D. A cap is added to the 5 end of the mRNA
Polypeptides are assembled from _____. hexoses glycerol nucleotides proteins amino acids
E. Amino acids Proteins are composed of amino acid monomers
Which of the following statements correctly describes the effect a nonsense mutation would have on a gene?
It introduces a premature stop codon into the mRNA.
Which of the following statements best describes the termination of transcription in prokaryotes?
RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript.
Where does translation take place?
Ribosomes Translation, or protein synthesis, occurs at the ribosome
What is the process called that converts the genetic information stored in DNA to an RNA copy?
Transcription DNA is transcribed to give an RNA copy
During RNA processing a(n) _____ is added to the 5' end of the RNA.
modified guanine nucleotide The 5' cap consists of a modified guanine nucleotide
Spliceosomes are composed of _____.
small RNAs and proteins
Which of the following molecules are produced by transcription?
Messenger RNA and ribozymes are both produced by transcription. Read about transcription and ribozymes.
DNA does not store the information to synthesize which of the following?
Organelles Synthesis of organelles is not directly coded in the DNA.
The promoter
The promoter is the region of DNA at which the process of transcription begins.
Suppose that the triplet of nucleotides indicated in bold (AGC) spans two codons, that is, CTA and GCC. If the triplet AGC were deleted from this DNA coding sequence, what effect would it have on the resulting protein? 5'-ATGCTAGCCTATCGTAAC-3'
The two flanking codons would be altered, but the rest of the amino acid sequence would be the same because there would be no frameshift. When a deletion of a set of three nucleotides that is out of frame to the reading frame of codons occurs, it only affects the codons flanking it. Once the ribosome reads past that point, the rest of the codons are in frame because a full triplet was deleted at one time.
A codon consists of _____ bases and specifies which _____ will be inserted into the polypeptide chain
three..... amino acids Three nucleotide bases make up a codon and specify which amino acid comes next in the sequence.
A nonsense mutation
causes an early Stop codon to occur.
Which of the following processes correctly describes alternative RNA splicing?
It can allow the production of proteins of different sizes and functions from a single mRNA.
True or false? A codon is a group of three bases that can specify more than one amino acid.
False A codon is a group of three bases that can specify only one amino acid.
True or false. A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated
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.
Which of these correctly illustrates the pairing of DNA and RNA nucleotides?
GTTACG CAAUGC In RNA, uracil takes the place of thymine.
Which of the following terms best describes the relationship between the newly synthesized RNA molecule and the DNA template strand?
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.
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
E. Translation Translation is the process by which information encoded in RNA is used to manufacture a polypeptide.
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?
Two The second and third codons in the new sequence are different from the original codons.
What is meant by translocation?
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.
A missense mutation
causes a wild-type amino acid to be replaced by a different amino acid.
Which of the following sequences of nucleotides are possible in the template strand of DNA that would code for the polypeptide sequence Phe-Leu-Ile-Val?
3-AAA-GAA-TAA-CAA-5
What is a ribozyme?
a biological catalyst made of RNA A number of examples of biological catalysts containing RNA have been discovered, including ribozymes, snRNAs, and ribosomes themselves.
Which of the following statements is the most current description of a gene? a DNA subunit that codes for a single complete protein a discrete unit of hereditary information that consists of a sequence of amino acids a unit of heredity that causes formation of a phenotypic characteristic a DNA sequence that is expressed to form a functional product: either RNA or polypeptide
A DNA sequence that is expressed to form a functional product: either RNA or polypeptide
The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. What is the result of this type of mutation? a polypeptide missing an amino acid a nonsense mutation a frameshift mutation a base-pair substitution
A polypeptide missing an amino acid
Why is a frameshift missense mutation more likely to have a severe effect on phenotype than a nucleotide-pair substitution missense mutation in the same protein?
A substitution missense affects only one codon, but a frameshift missense affects all codons downstream of the frameshift. Many genetic diseases are caused by missense mutations.
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. If the mutations occur within the same codon, only that codon (amino acid) will be altered.
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? A.RNA processing B.gene expression C. polypeptide formation D. transcription E. translation
D. Transcription Transcription is the process by which a DNA template is used for the manufacture of several different types of RNA.
What is the function of the release factor during translation in eukaryotes? It releases the ribosome from the ER to allow polypeptides into the cytosol. It releases the amino acid from its tRNA to allow the amino acid to form a peptide bond. It supplies a source of energy for termination of translation. It binds to the stop codon in the A site in place of a tRNA.
It binds to the stop codon in the A site in place of a tRNA.
If a DNA sequence is altered from TAGCTGA to TAGTGA, what kind of mutation has occurred?
Deletion The original sequence has lost the base C.
Think about the DNA coding sequence of a gene. If an A were swapped for a T, what kind of mutation could it cause and why?
It could cause a silent, missense, or nonsense mutation because those are the types that can be caused by a nucleotide-pair substitution like this one. When the sequence of bases in a gene is changed by a single nucleotide-pair substitution, it can have different effects on the product depending on where it is and whether or not the mutated codon codes for the same amino acid as the original codon.
What amino acid sequence will be generated, based on the following mRNA codon sequence? 5-AUG-UCU-UCG-UUA-UCC-UUG-3
Met-Ser-Ser-Leu-Ser-Leu
Which mutation(s) would not change the remainder of the reading frame of a gene sequence that follows the mutation(s)?
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.
Which of the following processes is an example of a post-translational modification?
Phosphorylation Enzymes can phosphorylate proteins to alter their activity.
Which of the following statements best describes the promoter of a protein-coding gene?
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.
Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the _____. binding of the anticodon to small subunit of the ribosome attachment of amino acids to rRNAs binding of ribosomes to mRNA binding of the anticodon to the codon and the attachment of amino acids to tRNAs
binding of the anticodon to the codon and the attachment of amino acids to tRNAs
A silent mutation
does not change the wild-type amino acid sequence.does not change the wild-type amino acid sequence.
How does the primary transcript in the nucleus of a eukaryotic cell compare to the functional mRNA?
the primary transcript is larger than the mRNA
How does the primary transcript in a prokaryotic cell compare to the functional mRNA?
the primary transcript is the same size as the mRNA
Which of the following processes is the first event to take place in translation in eukaryotes? the ribosome reaches a stop codon the small subunit of the ribosome recognizes and attaches to the 5 cap of mRNA binding of the larger ribosomal subunit to smaller ribosomal subunits base pairing of activated methionine-tRNA to AUG of the messenger RNA
the small subunit of the ribosome recognizes and attaches to the 5 cap of mRNA
Which of the following sequences shows a frameshift mutation compared to the wild-type mRNA sequence?
wild-type 5'-AUGCAUACAUUGGAGUGA-3' mutant 5'-AUGCAUACAUCUGGAGUGA-3' In order for an insertion or deletion to cause a frameshift mutation, it must cause the reading frame of each triplet of bases after it to be shifted by one or two places
