Chapter 17 Mastering Biology

A possible sequence of nucleotides in the template strand of DNA that would code for the polypeptide sequence phe-leu-ile-val would be

3' AAA-GAA-TAA-CAA 5'.

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

False

T or F? A codon is a group of three bases that can specify more than one amino acid

False

What is the function of GTP in translation?

GTP energizes the formation of the initiation complex, using initiation factors.

5' UTR E1 I1 E2 I2 E3 I3 E4 UTR 3' Which of the following is a useful feature of introns for this model?

Introns allow exon shuffling.

Which of the following best describes the significance of the TATA box in eukaryotic promoters?

It is the recognition site for a specific transcription factor.

What is the function of RNA polymerase?

It unwinds the double helix and adds nucleotides to a growing strand of RNA.

Garrod's information about the enzyme alteration resulting in alkaptonuria led to further elucidation of the same pathway in humans. Phenylketonuria (PKU) occurs when another enzyme in the pathway is altered or missing, resulting in a failure of phenylalanine (phe) to be metabolized to another amino acid: tyrosine. Tyrosine is an earlier substrate in the pathway altered in alkaptonuria. How might PKU affect the presence or absence of alkaptonuria?

It would have no effect, because tyrosine is also available from the diet

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

RNA processing

Which of the following molecules are produced by transcription?

Ribozymes Messenger RNA

Which of the following 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

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

three ... amino acid

Which of the following is a function of a signal peptide?

to translocate polypeptides across the ER membrane

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

Which of the following statements about ribozymes is/are correct?

-Ribozymes are RNA molecules that function as enzymes. -In some genes, intron RNA functions as a ribozyme and catalyzes its own excision. -A ribosome can be regarded as one large ribozyme.

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is

3' UCA 5'.

Which of the following is true?

A person that has a genetic mutation for a certain type of cancer may or may not get that disease.

Which of the following does not occur in prokaryotic gene expression, but does in eukaryotic gene expression?

A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end.

Which of the following is currently seen as the biggest downside to precision medicine?

Cost

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.

Which one of the following is true of tRNAs?

None of the above

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.

The initiator tRNA attaches at the ribosome's _____ site

P

Which of the following is true?

Patients with the same type of cancer may need different treatments

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

Phosphorylation

5' 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. What might result?

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

Where does translation take place?

Ribosome

The tRNA shown in the figure has its 3' end projecting beyond its 5' end. What will occur at this 3' end?

The amino acid binds covalently.

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

Translation can begin while transcription is still in progress

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?

We want to prevent any increase in mutation frequency.

You have pancreatic cancer and are considered a good candidate for precision medicine. Which of the following will have to be done?

You will have your genome sequenced.

Of the following, which is the most current description of a gene?

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

Which of the following DNA mutations is the most likely to be damaging to the protein it specifies?

a base-pair deletion

What is a ribozyme?

a biological catalyst made of RNA

What does a mutagen cause?

a change in the sequence of DNA

Polypeptides are assembled from

amino acids

Alternative RNA splicing

can allow the production of proteins of different sizes and functions from a single mRNA.

Translation occurs in the

cytoplasm

A frameshift mutation could result from

either an insertion or a deletion of a base

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

exons

The flow of information in a cell proceeds in what sequence?

from DNA to RNA to protein

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?

introns ... exons

You are a biotech engineer at Memorial-Sloan Kettering Cancer Center, specializing in studying gene sequences of tumors. Which of the following tumor types has your hospital focused on?

lung

RNA processing converts the RNA transcript into

mRNA

Which nucleic acid is translated to make a protein?

mRNA

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

many noncoding stretches of nucleotides are present in eukaryotic DNA.

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

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

modified guanine nucleotide

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. Which component of the complex described enters the exit tunnel through the large subunit of the ribosome?

newly formed polypeptide

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

several transcription factors

The enzyme polynucleotide phosphorylase randomly assembles nucleotides into a polynucleotide polymer. You add polynucleotide phosphorylase to a solution of ATP, GTP, and UTP. How many artificial mRNA 3 nucleotide codons would be possible?

27

The enzyme polynucleotide phosphorylase randomly assembles nucleotides into a polynucleotide polymer. You add polynucleotide phosphorylase to a solution of adenosine triphosphate and guanosine triphosphate. How many artificial mRNA 3 nucleotide codons would be possible?

8

Which of the following statements about mutations is false?

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

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.

Which of the following provides some evidence that RNA probably evolved before DNA?

DNA polymerase uses primer, usually made of RNA.

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

Deletion

Which of the following mutations would likely be most dangerous to a cell?

Deletion of one nucleotide

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

The "universal" genetic code is now known to have exceptions. Evidence for this can be found if which of the following is true?

If UGA, usually a stop codon, is found to code for an amino acid such as tryptophan (usually coded for by UGG only).

Why might a point mutation in DNA make a difference in the level of a protein's activity?

It might substitute a different amino acid in the active site.

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

RNA polymerase Aminoacyl-tRNA synthetase

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

The large ribosomal subunit joins the complex.

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

The molecule is digested by exonucleases since it is no longer protected at the 5' end.

The template strand of a gene contains this sequence: 3'-TAC TAG GCT AGT TGA-5'. A mutation occurs that changes the gene sequence to 3'-TAC TAG ACT AGT TGA-5'. How does this mutation affect the resulting amino acid sequence?

The mutation introduces a stop codon

What is meant by translocation?

The ribosome slides one codon down the mRNA.

How is translation initiated?

The small ribosomal subunit binds to the mRNA. The tRNA bearing methionine binds to the start codon. The large ribosomal subunit binds to the small one. The start codon signals the start of translation.

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

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

UUU

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?

a deletion of two nucleotides

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. This results in

a polypeptide missing an amino acid.

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

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

aminoacyl-tRNA synthetase

Spliceosomes are composed of

snRNPs and other proteins

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.

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

translation