Chapter 17: From Gene to Protein (Protein Synthesis) (MasteringBiology- Pearson)

Met-Ser-Cys-His

3′−TACAGAACGGTA−5′ Express the sequence of amino acids using the three-letter abbreviations, separated by hyphens (e.g., Met-Ser-His-Lys-Gly).

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

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?

introns allow exon shuffling

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

Met-Ala-Arg-Lys

5′−AUGGCAAGAAAA−3′ Express the sequence of amino acids using the three-letter abbreviations, separated by hyphens.

three ... amino acid

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

many noncoding stretches of nucleotides are present in eukaryotic DNA

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 _____.

either an insertion or a deletion of a base

A frameshift mutation could result from _____.

UUU

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

3' UCA 5'

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

3' AAA-GAA-TAA-CAA 5'

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

E site

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?

newly formed polypeptide

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?

introns... exons

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?

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

Alternative RNA splicing _____.

A-site

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

start/methionine- AUG stop codon- UAA, UAG, UGA amino acid- CAC, AUC, AAA, UGC, GCA, ACU

Codes.

a long string of adenine nucleotides

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

modified guanine nucleotide

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

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

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?

- 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.

How is translation initiated?

deletion

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

an addition mutation and a deletion mutation

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?

two

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?

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

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?

we want to prevent any increase in mutation frequency

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?

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

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

amino acids

Polypeptides are assembled from _____.

mRNA

RNA processing converts the RNA transcript into _____.

small RNAs and proteins

Spliceosomes are composed of _____.

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

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

exons

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

most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that are not translated

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?

27

The enzyme polynucleotide phosphorylase randomly assembles nucleotides into a polynucleotide polymer. 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?

from DNA to RNA to protein

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

a polypeptide missing an amino acid

The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in _____.

the amino acid binds covalently

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

the mutation introduces a stop codon

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 rules for base pairing between the third base of a codon and tRNA are flexible

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

several transcription factors

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

mRNA

Transcription/ RNA processing

tRNA and rRNA

Translation

cytoplasm

Translation occurs in the _____.

false

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

false; a codon can specify only one amino acid

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

met-ser-ser-leu-ser-leu

What amino acid sequence will be generated, based on the following mRNA codon sequence? 5' AUG-UCU-UCG-UUA-UCC-UUG 3'

a change in the sequence of DNA

What does a mutagen cause?

a biological catalyst made of RNA

What is a ribozyme?

the ribosome slides one codon down the mRNA

What is meant by translocation?

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

What is the function of GTP in translation?

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

What is the function of RNA polymerase?

transcription

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

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

translation

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

ribosome

Where does translation take place?

one addition and one deletion mutation

Which mutation(s) would not change the remainder of the reading frame of a gene sequence that follows the mutation(s)?

mRNA

Which nucleic acid is translated to make a protein?

a base-pair deletion

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

it is the recognition site for a specific transcription factor

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

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 does not occur in prokaryotic gene expression, but does in eukaryotic gene expression?

to translocate polypeptides across the ER membrane

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

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

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

- ribozymes - messenger RNA

Which of the following molecules are produced by transcription?

- RNA polymerase - Aminoacyl-tRNA synthetase

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

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

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

deletion of one nucleotide

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

phosphorylation

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

DNA polymerase uses primer, usually made of RNA

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

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

Which of the following statements about mutations is false?

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

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

translation can begin while transcription is still in progress

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

the large ribosomal subunit joins the complex

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

a deletion of two nucleotides

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?

each tRNA binds a particular amino acid

Which one of the following is true of tRNAs?

it might substitute a different amino acid in the active site

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

- specifies the amino acid sequence for a protein - contains exons

mRNA

- is a component of ribosomes - is the most abundant form of RNA

rRNA

- contains an anticodon - has amino acids covalently attached

tRNA