Chapter 17

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'

Which of the following statements about mutations is false?

A knock-out mutation results in a total absence of the mutated protein.

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

A site

Which of the following processes occurs when termination of translation takes place?

A stop codon is reached.

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.

At which site do new aminoacyl tRNAs enter the ribosome during elongation?

A-site

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.

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

The tRNA anticodon, GAC, is complementary to the mRNA codon with the sequence _____.

CUG

In the diagram below, the two blue strands represent _____.

DNA

If a DNA sequence is altered from TAGCTGA to TAGTGA, what kind of mutation has occurred?

Deletion

True or false. A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated.

False

True or false? A codon is a group of three bases that can specify more than one amino acid.

False

Which of these correctly illustrates the pairing of DNA and RNA nucleotides?

GTTACG CAAUGC

The initiator tRNA attaches at the ribosome's _____ site.

P

Which of the following processes is an example of a post-translational modification?

Phosphorylation

Which of the following steps occurs last in the initiation phase of translation?

The large ribosomal subunit joins the complex.

Which of the following statements best describes the promoter of a protein-coding gene?

The promoter is a nontranscribed region of a gene.

What is meant by translocation?

The ribosome slides one codon down the mRNA.

What is the process called that converts the genetic information stored in DNA to an RNA copy?

Transcription

During RNA processing a(n) _____ is added to the 3' end of the RNA.

a long string of adenine nucleotides

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

Polypeptides are assembled from _____.

amino acids

What enzyme catalyzes the attachment of an amino acid to tRNA?

aminoacyl-tRNA synthetase

Translation occurs in the _____.

cytoplasm

The RNA segments joined to one another by spliceosomes are _____.

exons

What type of bonding is responsible for maintaining the shape of the tRNA molecule shown in the figure?

hydrogen bonding between base pairs

Which nucleic acid is translated to make a protein?

mRNA

Which of the following molecules are produced by transcription?

mRNA and ribozymes

A ______ mutation causes an early Stop codon to occur.

nonsense

DNA does not store the information to synthesize which of the following?

organelles

Which one of the following is true of tRNAs?

None of the listed answers is correct.

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

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

Which of the following processes occurs in eukaryotic gene expression?

A cap is added to the 5 end of the mRNA.

Transcription begins at a promoter. What is a promoter?

A site in DNA that recruits the RNA Polymerase

What is the function of the release factor during translation in eukaryotes?

It binds to the stop codon in the A site in place of a tRNA.

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.

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.

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.

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.

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.

In the diagram below, the gray unit represents _____.

RNA polymerase

Which of the following molecules is/are produced by translation? Include molecules that are subject to further modification after initial synthesis.

RNA polymerase and aminoacyl-tRNA synthetase

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.

What name is given to the process in which pre-mRNA is edited into mRNA?

RNA processing

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.

Use the codon table to determine which mRNA triplets code for the amino acid cysteine, Cys.

There are only two mRNA triplets that code for the amino acid Cys: UGU and UGC.

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

Which of the following terms best describes the relationship between the newly synthesized RNA molecule and the DNA template strand?

complementary

Which of the following statements is the most current description of a gene?

a DNA sequence that is expressed to form a functional product: either RNA or polypeptide

What is a ribozyme?

a biological catalyst made of RNA

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

What is the name of the process shown in the diagram?

initiation (of translation)

RNA processing converts the RNA transcript into _____.

mRNA

A ______ mutation causes a wild-type amino acid to be replaced by a different amino acid.

missense

During RNA processing a(n) _____ is added to the 5' end of the RNA.

modified guanine nucleotide

Use the following information to answer the question. A part of an mRNA molecule with the following sequence is being read by a ribosome: 5-CCG-ACG-3 (mRNA). The following charged transfer RNA molecules (with their anticodons shown in the 3 to 5 direction) are available. Two of them can correctly match the mRNA so that a dipeptide can form. Which of the following dipeptides will form from this mRNA?

proline-threonine

Where does translation take place?

ribosome

Transcription in eukaryotes requires which of the following molecules in addition to RNA polymerase?

several transcription factors

A ______ mutation does not change the wild-type amino acid sequence.

silent

Spliceosomes are composed of _____.

small RNAs and proteins

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

In the diagram below, the green unit represents _____.

the promoter

Which of the following processes is the first event to take place in translation in eukaryotes?

the small subunit of the ribosome recognizes and attaches to the 5 cap of mRNA

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

A codon consists of _____ bases and specifies which _____ will be inserted into the polypeptide chain.

three ... amino acid

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?

transcription

What name is given to the process in which the information encoded in a strand of mRNA is used to construct a protein?

translation

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'