Deck 13: The Genetic Code and Transcription

Question 1

The genetic code is fairly consistent among all organisms.The term often used to describe such consistency in the code is _________.

A)overlapping
B)universal
C)exceptional
D)trans- specific
E)None of the above

Answer 1

universal

Question 2

The finding that some phage genes have multiple initiation sites is evidence against what characteristic of the genetic code?

A)The genetic code is commaless.
B)The genetic code is unambiguous.
C)The genetic code is a triplet code.
D)The genetic code is universal.
E)The genetic code is nonoverlapping.

Answer 2

E

Question 3

Eukaryotic transcription is different than bacterial transcription because eukaryotic transcription_________ .

A)occurs in the cytoplasm
B)requires the uncoiling of the chromatin fiber
C)does not require general transcription factors to initiate transcription
D)does not require the mRNA to be modified
E)only requires one RNA polymerase

Answer 3

requires the uncoiling of the chromatin fiber

Question 4

When scientists were attempting to determine the structure of the genetic code,Crick and coworkers found that when three base additions or three base deletions occurred in a single gene,the wild- type phenotype was sometimes restored.These data supported the hypothesis that_________ .

A)the code is triplet
B)the code contains internal punctuation
C)there are three amino acids per base
D)the code is overlapping
E)AUG is the initiating triplet

Question 5

It has been recently determined that the gene for Duchenne muscular dystrophy DMD is more than 2000 kb kilobases in length; however,the mRNA produced by this gene is only about 14 kb long.What is a likely cause of this discrepancy?

A)The exons have been spliced out during mRNA processing.
B)There are more amino acids coded for by the DNA than by the mRNA.
C)The DNA represents a double- stranded structure,whereas the RNA is single- stranded.
D)The introns have been spliced out during mRNA processing.
E)When the mRNA is produced,it is highly folded and therefore less long.

Question 6

In 1964,Nirenberg and Leder used the triplet binding assay to determine specific codon assignments.A complex of which of the following components was trapped in the nitrocellulose filter?

A)charged tRNA,RNA triplet,and ribosome
B)ribosomes and DNA
C)sense and antisense strands of DNA
D)free tRNAs
E)uncharged tRNAs and ribosomes

Question 7

When considering the initiation of transcription,one often finds consensus sequences located in the region of the DNA where RNA polymerases)binds.Which of the following is a common consensus sequence?

A)any trinucleotide repeats
B)satellite DNAs
C)TATAAT
D)TTTTAAAA
E)GGTTC

Question 8

A particular mRNA is 300 nucleotides long.If a mutation in the middle of the sequence changed a codon from a AAA to a UAA then what would be a reasonable prediction?

A)The protein coded by this mRNA would be the same size.
B)The protein coded by this mRNA would not form due to a failure in initiation.
C)The protein coded by this mRNA would be longer.
D)The protein coded by this mRNA would kill the cell.
E)The protein coded by this mRNA would be shorter.

Question 9

Which of the following is true regarding the genetic code?

A)The genetic code is considered to not be universal.
B)The genetic code has three start codons and one stop codon.
C)The genetic code is degenerate.
D)The genetic code is overlapping.
E)The genetic code is ambiguous.

Question 10

Which transcription factor binds directly to the TATA- box sequence?

A)enhancers
B)TFIIC
C)TFIIA
D)TFIID
E)TFIIB

Question 11

Which of the following bacterial RNA polymerase subunits is found in the holoenzyme,but not the core enzyme?

A)fi' beta prime
B)m omega
C)a sigma
D)fi beta
E)a alpha)

Question 12

Due to the wobble hypothesis,which position in the codon,if changed to a different nucleotide,would be least likely to cause a change in the amino acid encoded?

A)second nucleotide of the codon
B)first nucleotide of the codon
C)third nucleotide of the codon
D)any nucleotide of the codon.
E)Either the first or second nucleotide of the codon.

Question 13

A mutation of what type of sequence is predicted to have the greatest effect on the rate of transcription?

A)silencer
B)proximal- promoter element
C)termination sequence
D)enhancer
E)core promoter

Question 14

An intron is a section of _________ .

A)protein that is clipped out posttranslationally
B)the transfer RNA tRNA)that binds to mRNA codon
C)DNA that is removed during DNA processing
D)RNA that is removed during RNA processing
E)the carbohydrate that serves as a signal for RNA transport

Question 15

If there were 75 naturally occurring amino acids then what is the smallest codon size?

A)1
B)2
C)3
D)4
E)5

Question 16

An mRNA that is being produced comes off of the _________.

A)coding strand in both bacteria and eukaryotes
B)template strand in both bacteria and eukaryotes
C)template strand in bacteria and the coding strand in eukaryotes
D)coding strand in bacteria and the template strand in eukaryotes
E)coding or template strand in both bacteria and eukaryotes depending upon the species

Question 17

The relationship among a gene,a messenger RNA,and a protein is that_________ .

A)proteins make mRNA,which then make genes
B)genes make proteins,which then make mRNA
C)genes make mRNA,which then make proteins
D)mRNAs make genes,which then make proteins
E)mRNAs make proteins,which then make genes

Question 18

Which mRNA modification is likely absent if the mRNA is degrading prematurely from the 5' end of the mRNA?

A)addition of the 3' polyadenylated tail
B)splicing together of exons
C)addition of the 7- methylguanosine cap to the 5' end
D)RNA editing
E)removal of introns

Question 19

What is the initiator triplet in both bacteria and eukaryotes? What amino acid is recruited by this triplet?

A)UAA,UGA,or UAG; no amino acid called in
B)AUG; methionine
C)AUG; arginine
D)UAA,UGA,or UAG; arginine
E)UAA,UGA,or UAG; methionine

Question 20

If one compares the base sequences of related genes from different species,one is likely to find that corresponding _________ are usually conserved,but the sequences of __________are much less well conserved.

A)introns; proteins
B)introns; chaperons
C)introns; exons
D)exons; introns
E)chaperons; exons

Question 21

Reading the RNA sequences in a 5' to 3' direction,a base at the first position of an anticodon on the tRNA would pair with a base at the_________ position of the mRNA.

Question 22

"Breaking the genetic code" has been referred to as one of the most significant scientific achievements in modern times.Describe in outline or brief statement form the procedures used to break the code.

Question 23

Explain the "wobble hypothesis" and why it allows a single tRNA to recognize more than one codon.

Question 24

In the context of molecular genetics,how does one reconcile the terms overlapping genes and nonoverlapping code?

Question 25

The type of RNA modification that requires guide RNAs is_________ .

A)RNA editing
B)splicing together of exons
C)addition of the 7- methylguanosine cap to the 5' end
D)addition of the 3' polyadenylated tail
E)removal of introns

Question 26

In which cellular organelle do the three posttranscriptional modifications often seen in the maturation of mRNA in eukaryotes occur?

A)Golgi
B)mitochondrion
C)cytoplasm
D)lysosome
E)nucleus

Question 27

From the late 1950s to the mid- 1960s,numerous experiments using in vitro cell- free systems provided information on the nature of the genetic code.Briefly explain how the use of polynucleotide phosphorylase and the triplet binding assay were used to decipher the genetic code and why the triplet binding assay was more precise.

Question 28

Which of the following intron groups is matched appropriately with a true statement?

A)Spliceosomal introns are removed using the catalytic ability of the intron itself.
B)Group I introns are removed from rRNAs that are found in mitochondria and chloroplasts.
C)Group I introns are removed from rRNAs using large protein- based enzyme complexes.
D)Spliceosomal introns are removed using large protein- based enzyme complexes.
E)Group II introns are removed from mRNA in mammals.

Question 29

Describe the effects of mutating a sigma factor gene in bacteria.

Question 30

In a particular bacterial mutant,a specific gene is not producing a mRNA or the corresponding protein.Researchers sequence the gene and determine that there are no mutations in the coding portion of the gene.What could explain these observations?

Question 31

Describe a difference between the RNA polymerases of eukaryotes and prokaryotes.

Question 32

Suppose that in the use of polynucleotide phosphorylase,nucleotides A and C are added in a ratio of 1A:5C.What is the probability that an AAA sequence will occur?

Question 33

Describe how rho- dependent termination occurs in bacteria.

Question 34

There is some indication that the code is in some way ordered; a certain pattern exists.Describe an observation that supports this view.

Question 35

Sidney Brenner argued that the code was nonoverlapping because he considered that coding restrictions would occur if it were overlapping.A second major argument against an overlapping code involved the effect of a single nucleotide change.In an overlapping code,how many adjacent amino acids would be affected by a single nucleotide change? In a nonoverlapping code,how many amino acids would be affected?

Question 36

What are three observations that suggested eukaryotic RNA was an intermediate between DNA and protein.

Question 37

The finding that virtually all organisms use the same genetic code provides the basis for declaring that the code is universal.Name at least two exceptions to such universality.

Question 38

Write a sequence of mRNA that codes for five amino acids and the mRNA should contain proper punctuation and polarity.

Question 39

A particular mRNA makes a protein that has a unformylated methionine as its first amino acid.Did this mRNA come from a bacterial or a eukaryotic cell? Explain.

Question 40

Describe the direction of information flow in living systems.Use appropriate,scientific terms in your description.

Question 41

In eukaryotes,which three factors appear to encourage the specific association of RNA polymerases to a specific region of DNA?

Question 42

List four possible reasons that explain the importance of introns.

Question 43

What are four ways that mRNA can be modified?

Question 44

A researcher is looking at a cellular sample using an electron microscope.They observe that while mRNA is being transcribed from the DNA that ribosomes are binding to the mRNA to make proteins.Is this sample from a bacterial or a eukaryotic cell?

Question 45

What is meant by the term heterogeneous nuclear RNA hnRNA ?