Ch. 17 - Unit 4 - BIOL 101

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 function of a signal peptide?

It helps target a protein to the ER.

Which of the following statements describes the effect of a nonsense mutation on a gene?

It introduces a premature stop codon into the mRNA.

Which of the following statements correctly describes a ribozyme?

It is an RNA with catalytic activity.

Which of the following statements about the function of RNA polymerase is correct?

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

Rank the following mutations with respect to their likelihood of affecting the structure of the polypeptide (from most likely to affect structure to least likely). 1. insertion mutation in the middle of an intron 2. deletion of 3 bases crossing an intron-exon border 3. substitution mutation at the third position of a codon 4. substitution mutation at the second position of a codon

2, 3, 4, 1

Given a DNA molecule with the sequence of bases 5'-ATTGCA-3', what would be the sequence of the complementary strand? (It will be helpful to draw the DNA molecule when answering the question.)

3'-TAACGT-5'

Which of these is currently considered the best definition of a gene?

A gene codes for either a polypeptide or an RNA molecule

The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following statements to be true?

A gene from an organism can theoretically be expressed by any other organism.

Which of the following statements about mutations is false?

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

Which of the following statements best supports the one gene-one enzyme hypothesis?

A mutation in a single gene can result in a defective protein.

Which of the following describes the most likely effect that a single base substitution in the middle of gene's sequence will have on the protein the gene encodes?

A single amino acid would change because pairing of mRNA and tRNA in the ribosome would change.

During the elongation phase of translation, which site in the ribosome represents the first location where a codon pairs with an anticodon?

A site

Transcription begins at a promoter. What is a promoter?

A site in DNA that recruits the RNA Polymerase

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

Which of the following properties is associated with a protein that will be secreted from a eukaryotic cell?

Its signal sequence must target it to the ER

Which of the following shows the flow of genetic information?

DNA to RNA to protein

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

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 the following statements correctly describes Archibald Garrod's hypothesis for how "inborn errors of metabolism" such as alkaptonuria occur?

Genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes.

Once researchers identified DNA as the molecule responsible for transmitting heritable traits, they asked how information was transferred from the DNA in the nucleus to the site of protein synthesis in the cytoplasm. Which of the following statements correctly describes the mechanism of information transfer that accomplishes this task in eukaryotes?

Messenger RNA is transcribed from a single gene and transfers information to the cytoplasm, where protein synthesis takes place.

Which of the following best describes the redundancy in the genetic code?

More than one codon can specify the addition of the same amino acid.

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 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.

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

Organelles

Which answer correctly compares prokaryotic and eukaryotic codons?

Organisms utilize codons that are nearly universal among all organisms

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.

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

Translation can begin while transcription is still in progress.

What does a mutagen cause?

a change in the sequence of DNA

A single base substitution mutation is likely to have a less harmful effect when the base change results in which of the following?

a codon that specifies the same amino acid as the original codon

While characterizing an error-prone organism, researchers found that each of the following types of mutations occurred immediately downstream of the translation start site. Which type of mutation is likely to have the most serious effect on the function of the polypeptide product?

a deletion of two nucleotides

Generally speaking, which of the following mutations would most severely affect the protein coded for by a gene?

a frameshift deletion at the beginning of the gene

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

Which of the following mutations would be most likely to have a harmful effect on an organism?

a single nucleotide insertion downstream of, and close to, the start of the coding sequence

Translation termination occurs when a ribosome interacts with which of the following structures?

a stop codon

Post-translational modifications of proteins may include which of the following processes?

addition of carbohydrates to form a glycoprotein

Polypeptides are assembled from _____

amino acids

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

aminoacyl-tRNA synthetase

Amino acids are attached to tRNA by enzymes called _______

aminoacyl-tRNA synthetase.

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

attachment of amino acids to tRNAs

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

complementary

The anticodon of a particular tRNAtRNA molecule is

complementary to the corresponding mRNA codon

Translation occurs in the _____.

cytoplasm

The RNA segments joined to one another by spliceosomes are _____

exons

A section of DNA has the base sequence shown in #1. A mutation in this DNA strand results in the base sequence shown in #2. What type of mutation does this change represent?#1 5' - AGCGTTACCGT-3'#2 5'-AGGCGTTACCGT-3'

frameshift mutation

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

from DNA to RNA to protein

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

P

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

Phosphorylation

If a bacteria contained a mutant aminoacyl-tRNA synthetase that attaches a lysine instead of the normal phenylalanine to tRNAs with the anticodon AAA which of the following would occur?

Proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU.

Which of the following processes occurs as part of transcription?

RNA is synthesized

In eukaryotes, there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a protein?

RNA polymerase II

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

Which of the following statements about RNA processing is correct?

Ribozymes may function in RNA splicing

___________ of translation happens when the ribosome hits a stop codon on the mRNA.

Termination

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

The large ribosomal subunit joins the complex.

Which of the following is most likely to occur if a researcher removes the 5' cap and poly-A tail of an mRNA and inserts the mRNA molecule into a eukaryotic cell?

The molecule will be degraded by enzyme

Where does translation take place?

ribosome

Which component is directly involved in translation?

ribosome

In eukaryotic cells, transcription cannot begin until

several transcription factors have bound to the promoter.

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

silent

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

simultaneous transcription and translation of the same mRNA

Spliceosomes are composed of _____.

small RNAs and proteins

The RNA that has an amino acid attached to it, and that binds to the codon on the mRNA, is called a ____

tRNA

During transcription in eukaryotes, a type of RNA polymerase called RNA polymerase II moves along the template strand of the DNA in the 3'→5' direction. However, for any given gene, either strand of the double-stranded DNA may function as the template strand. For any given gene, what ultimately determines which DNA strand serves as the template strand?

the base sequence of the gene's promoter

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

Where does RNA polymerase begin transcribing a gene into mRNA?

it starts after a certain nucleotide sequence called a promoter

According to the central dogma, which of the following intermediate molecules correctly completes the flow chart describing the flow of information in a cell blank? DNA - ________ - Proteins

mRNA

RNA processing converts the RNA transcript into _____.

mRNA

Which nucleic acid is translated to make a protein?

mRNA

Which of the following molecular structures contains codons?

mRNA

Which of the following molecules directly participates in the process of translation?

mRNA, tRNA, and rRNA

Which of the following is true of RNA processing?

nucleotides are added at both ends of the RNA

In eukaryotes which of the following is the first step in translation?

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

Which of the following characteristics is directly related to the coding of a single amino acid during the process of translation?

the three-base sequence of mRNA

In the structure of many eukaryotic genes, individual exons parallel which of the following?

the various domains of the protein product

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

three, amino acid

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

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?

transcription

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

transcription factors

The process, performed by the ribosome, of reading mRNA and synthesizing a protein is called __________

translation

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

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

Which of the following clues would tell you if a cell is prokaryotic or eukaryotic?

whether or not the cell is compartmentalized by internal membranes

Which three statements correctly describe the processing that takes place before a mature mRNA exits the nucleus?

- A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA. - Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes. - A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA.

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

- 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 terms associated with transcription describe regions of nucleic acid?

- promoter - terminator - gene

How is translation initiated?

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

Which of the following is true of a codon?

It can be either in DNA or in RNA.

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

__________ of translation always happens at the start codon of the mRNA.

Initiation

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.

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.

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

It is the recognition site for the binding of a specific transcription factor.

Which one of the following statements is true of tRNAs?

None of the listed answers are correct.:- There are four types of tRNA.- Each tRNA binds a particular codon.- tRNAs are double-stranded.- tRNAs carry special sequences known as codons.

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

The promoter is a nontranscribed region of a gene.

Your body contains tens of thousands of different proteins, each with a specific structure and function. The unique three-dimensional shape of each of these diverse proteins is based on several superimposed levels of structure. Which of the following is an accurate statement about proteins?

The primary structure of a protein is the order of amino acids in a polypeptide, as coded for by the DNA of a gene

What is meant by translocation?

The ribosome slides one codon down the mRNA.

Which of the following best explains the observation that in bacteria, there are 61 mRNA codons that specify an amino acid, but only 45 tRNAs?

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

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

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

Which of the following changes in an exon is most likely to result in a nonfunctional protein product?

a base-pair deletion

What is a ribozyme?

a biological catalyst made of RNA

Which of the following molecules are produced by transcription?

messenger RNA and ribozymes

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

A ___________ mutation causes an early Stop codon to occur.

nonsense

Which answer correctly compares the primary transcript in the nucleus of a eukaryotic cell with the functional mRNA?

the primary transcript is larger than the mRNA

Which answer correctly compares the primary transcript in a prokaryotic cell with the functional mRNA?

the primary transcript is the same size as the mRNA