Chapter 17 Practice Quiz

Put the following events of elongation in prokaryotic translation in chronological order. 1.Binding of mRNA with small ribosomal subunit 2.Recognition of initiation codon 3.Complementary base pairing between initiator codon and anticodon of initiator tRNA 4.Base pairing of the mRNA codon following the initiator codon with its complementary tRNA 5.Attachment of the large subunit

1, 2, 3, 5, 4

The anticodon loop of the first tRNA that will complement this mRNA is

3' GGC 5'

Put the following events of bacterial transcription in chronological order. 1.Sigma binds to the promoter region. 2.The double helix of DNA is unwound, breaking hydrogen bonds between complementary strands. 3.Sigma binds to RNA polymerase. 4.Sigma is released. 5.Transcription begins.

3, 1, 2, 5, 4

Use this model of a eukaryotic transcript to answer the following question(s).E = exon and I = intron5' 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' UTR E1 E2 E3 E4 UTR 3'

Which of the following, if missing, would usually prevent translation from starting in eukaryotes?

5' cap or AUG codon

If the sequence in the coding strand of DNA for a particular amino acid is 5'AGT3', then the anticodon on the corresponding tRNA would be ________.

5'ACU3'

During elongation, which site in the ribosome represents the location where a codon is being read?

A site

A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is ________.

AAA

There are 61 codons that each specify the addition of a specific amino acid, and 3 stop codons for which there is no corresponding amino acid. However, there are only about 40 tRNA molecules, representing 40 anticodons. How is that possible?

An anticodon forms hydrogen bonds with the codon; it must match the first two bases of the codon but is less specific with respect to the third base.

Codons are three-base sequences that specify the addition of a single amino acid. How do eukaryotic codons and prokaryotic codons compare?

Codons are a nearly universal language among all organisms.

Use the following information to answer the question(s) below.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) in the ribosome already.Where does tRNA #2 move to after this bonding of lysine to the polypeptide?

E site

As scientists were unraveling the mysteries associated with transcription and translation in eukaryotes, they discovered there was not a one-to-one correspondence between the nucleotide sequence of a gene and the base sequence of the mRNA it codes for. They proposed the genes-in-pieces hypothesis. How can the genes-in-pieces hypothesis be explained?

Introns are noncoding segments of DNA that are present in the initial transcript, but are removed by splicing.

In the figure associated with this question, what is the function of the ACC sequence at the 3' end?

It attaches to an amino acid

In the figure associated with this question, what is the function of the AGU on the loop of the tRNA?

It base pairs with a codon of mRNA.

What is the function of the group of amino acids on the RNA polymerase, called the rudder?

It moves template and non-template strands of DNA through channels inside the enzyme.

The enzyme complex associated with DNA in the associated figure is ________.

RNA polymerase

Use this model of a eukaryotic transcript to answer the following question(s).E = exon and I = intron5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3'Suppose that an induced mutation removes most of the 5' end of the 5' UTR of an mRNA. What is most likely to happen?

Removal of the 5' UTR also removes the 5' cap and the mRNA will quickly degrade.

Which one of the following statements about RNA processing is TRUE?

Ribozymes may function in RNA splicing.

The ribosome-binding site of prokaryotes is also known as the ________.

Shine—Dalgarno sequence

The tRNA shown with the previous question has its 3' end projecting beyond its 5' end. What will occur at this 3' end?

The amino acid binds covalently.

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' bases AC. Which of the following hypotheses describes the most likely result?

The amino acid methionine will not become covalently bound.

In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after she has removed its 5' cap and poly-A tail. Which of the following would you expect her to find?

The molecule is digested by enzymes because it is not protected at the 5' end.

How are RNA hairpin turns related to transcriptional termination in E. coli?

The turns are formed from complementary base pairing and cause separation of the RNA transcript and RNA polymerase.

Which of the following statements is TRUE about protein synthesis in prokaryotes?

Translation can begin while transcription is still in progress.

The figure associated with this question represents a tRNA that recognizes and binds a particular amino acid (in this instance, phenylalanine). Which codon on the mRNA strand codes for this amino acid?

UUC

You want to engineer a eukaryotic gene into a bacterial colony and have it expressed. What must be included in addition to the coding exons of the gene?

a bacterial promoter sequence

What is responsible for termination of transcription in eukaryotic protein-coding genes?

a polyadenylation, or poly(A), signal

Which of the following mutations is most likely to cause a phenotypic change?

a single nucleotide deletion in an exon coding for an active site

During elongation, RNA polymerase has three prominent channels, or grooves. These channels provide sites for all of the following EXCEPT ________.

a site for the exit of the diphosphates removed from the nucleotide triphosphates

How does termination of translation take place?

a stop codon is reached

A ribozyme is ________.

an RNA with catalytic activity

Use this model of a eukaryotic transcript to answer the following question(s).E = exon and I = intron5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3'When the spliceosome binds to the transcript shown above, it can attach ________.

at certain sites along an intron

David Pribnow studied the base sequences of promoters in bacteria and bacterial viruses. He found two conserved regions in these promoters (the −10 box and the −35 box). These two regions of the promoter ________.

bind the sigma subunit that is associated with RNA polymerase

Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the ________.

binding of the anticodon to the codon and the attachment of amino acids to tRNAs

The anticodon of a particular tRNA molecule is ________.

complementary to the corresponding mRNA codon

Which of the following occurs in prokaryotes but not in eukaryotes?

concurrent transcription and translation

In comparing DNA replication with RNA transcription in the same eukaryotic cell, only DNA replication ________.

incorporates the entire template molecule in the product

Translation directly involves ________.

mRNA, tRNA, ribosomes, and GTP

Refer to the figure associated with this question. The mRNA is smaller than the length of the DNA that codes for it because ________.

post-transcriptional modification removes the introns

Eukaryotes have three nuclear RNA polymerases. The primary function of RNA polymerase II is transcription of ________.

protein-coding genes

What molecules in the spliceosome catalyze the intron removal reactions?

ribozymes

In eukaryotic cells, transcription cannot begin until ________.

several transcription factors have bound to the promoter

In E. coli, if RNA polymerase is missing ________, then transcription initiation would not occur at the appropriate initiation sites.

sigma

Death cap mushrooms produce a substance called alpha-amanitin. Alpha-amanitin efficiently blocks synthesis of mRNA, but not of tRNA or rRNA, in eukaryotic organisms. This is possible because alpha-amanitin efficiently interferes with ________.

the action of RNA polymerase II, but not RNA polymerase I or III

What ensures that the correct amino acid is added during translation?

the anticodon of a properly formed aminoacyl tRNA

There should be a strong positive correlation between the rate of protein synthesis and ________.

the number of ribosomes

Which molecule or reaction supplies the energy for polymerization of nucleotides in the process of transcription?

the phosphate bonds in the nucleotide triphosphates that serve as substrates

There are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that ________.

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?

the small subunit of the ribosome recognizing and attaching to the 5' cap of mRNA

Some viruses can be crystallized and their structures analyzed. One such virus is yellow mottle virus, which infects beans. This virus has a single-stranded RNA genome containing about 6300 nucleotides. Its capsid is 25—30 nm 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

Once a peptide bond 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?

translocation