Assignment 3

The final amino acid in a polypeptide chain is encoded by a codon near the ______.

3' end of the mRNA

The polyadenylation signal sequence in eukaryotic mRNA is ______.

5' AAUAAA 3'

To begin each round of elongation during translation, the tRNA carrying the next amino acid to be added to the polypeptide chain binds to the ___ site of the ribosome.

A (aminoacyl)

Which of the following statements accurately describes variations in the sizes and numbers of introns in eukaryotic organisms?

A gene can have none or many introns and introns can be short or very long (hundreds of kilobases long).

Which of the following are features of eukaryotic translation not seen in prokaryotic translation?

A single AUG for synthesis of one type of polypeptide per mRNA, Small ribosomal subunit interacts with 5' cap

Which of the following are features of transcription in eukaryotes only?

Addition of 5' cap to mRNA, Alternative splicing of transcripts can produce multiple types of polypeptides, Presence of multiple types of RNA polymerases

In order to charge a tRNA, ATP, a specific transfer RNA and a specific amino acid all bind to which enzyme?

Aminoacyl-tRNA synthetase

Where on the tRNA is the amino acid attachment site?

At the 3' end

What are snRNPs?

Components of the spliceosome

used to study protein-DNA interactions

DNase I footprinting

In prokaryotic cells, formation of the initiation complex requires the binding of tRNAifMet to the __________ site of the ribosome.

P

Which of the following are features of a superrepressor mutation which affects the lac operon?

Prevents the repressor from binding to the inducer, Occurs in lacI, Causes constant repression of the lac operon

bacterial communication system that allows them to adjust their behavior according to their population density

Quorum sensing

Which of the following pieces of evidence suggested that RNA could function as the intermediary between DNA and protein?

RNA can base pair with DNA, Radioactive uracil was incorporated into molecules in the nucleus and then exported to the cytoplasm

A ribozyme is a(n) ____.

RNA molecule with catalytic activity

Which of the following statements accurately describes the presence of exons and introns in protein-coding genes in eukaryotes?

While most protein-coding eukaryotic genes have introns, a few have none.

The inducer of the genes for lactose utilization is a molecule called ____________. (binds to lac repressor and prevents it from binding to DNA)

allolactose

protein that undergoes a reversible change in conformation when bound to another molecule

allosteric protein

In mammals, what process is used to produce two types of antibodies (secreted and membrane-embedded) in a B cell?

alternative splicing

The single-stranded region at the 3' end of a transfer RNA is the location where a(n) ______ becomes attached.

amino acid

In the lac operon, some of the nucleotides of the operator are also part of the ______.

promoter

Transcription in prokaryotes begins when the RNA pol holoenzyme binds to specific DNA sequences in a region called the ____________.

promoter

Translation is the process of synthesizing ____.

protein from an RNA template

The DNase I footprinting technique is used to show where ____________ bind to _____________________.

protein, DNA/RNA

If an intron interrupts the 5' UTR of an mRNA, the start codon ____.

won't be in the first exon

Which statement describes the mechanism of action of the spliceosome?

Introns are removed using two sequential cuts.

When a polypeptide is synthesized, the first amino acid to be put in place is located at the ______.

N terminus

During translation, a polypeptide grows from its _____.

N terminus to its C terminus

Enzymes known as _____________ are responsible for attaching amino acids to their corresponding tRNAs.

aminoacyl-tRNA synthetases

A series of three nucleotides in transfer RNA that is complementary to a codon in messenger RNA is called a(n) _________ .

anitcodon

The order in which amino acids are added to a polypeptide chain is determined by hydrogen bonding between each codon and the ______ of the tRNA carrying the amino acid.

anticodon

During elongation, the ______ of the incoming tRNA binds to the ______ of the mRNA.

anticodon, codon

The 5' and 3' untranslated regions of a mature eukaryotic mRNA ____.

are located within exons, facilitate efficient translation

In prokaryotes, ribosomes can generally initiate translation _______.

at several positions along a single mRNA molecule

The function of an aminoacyl-tRNA synthetase enzyme is to catalyze the ______.

attachment of an amino acid to its appropriate tRNA

The Lac repressor protein binds to the operator and ______.

blocks transcription

The addition of a methylated "backward G" to the 5' end of a eukaryotic mRNA is a process known as ______.

capping

Pathways that break down complex molecules into smaller units are termed _______________, while pathways that construct end product molecules from simpler units are called ___________.

catabolic, anabolic

A transfer RNA that has an amino acid attached to its 3' end is called a(n) _________________ tRNA.

charged, aminoacyl

For protein-encoding genes, the RNA-like strand is also called the ________ strand.

coding, sense, nontemplate

A series of three nucleotide bases that specifies a particular amino acid

codon

Which of the following is not a feature of transfer RNA molecules?

codon

When scientists were determining the genetic code, they found evidence that genes are ___________ with their encoded polypeptides. In other words, the order of bases in a gene corresponds to the order of amino acids in the encoded polypeptide.

colinear

an organism that synthesizes certain proteins all the time, regardless of environmental conditions

constitutive

A mutation in the operator that renders it nonfunctional will cause the ______.

constitutive expression of the lac operon

small molecule that binds to a protein and changes its conformation

effector

A eukaryotic promoter differs from a prokaryotic promoter because _____.

eukaryotic promoters are bound by histone proteins that must be released

Regions of DNA that are represented in a mature transcript are_______.

exons

The synthesis of RNAs and proteins according to the instructions encoded in DNA

gene expression

In a eukaryotic gene, the number of nucleotides in the DNA sequence is ______ the number of nucleotides in the mature mRNA sequence.

higher than

The E. coli complete RNA polymerase ______ consists of the core enzyme plus the sigma factor.

holoenzyme

If an intron interrupts a codon, the three nucleotides of the codon will be present ____.

in two different, successive exons

Cellular extracts that, with the addition of mRNA, synthesize polypeptides in a test tube

in vitro translational systems

The binding of the _________ to the repressor causes an allosteric effects that abolishes the repressor's ability to bind to the operator.

inducer

The lacIS mutants cannot bind the_______________, but can still bind to the _________________. As a result, their lac operon is constantly repressed, regardless of lactose availability.

inducer, operator

_________ are intervening sequences of DNA that are not represented in mature mRNA.

introns

An mRNA is monocistronic if _____.

it codes for a single polypeptide

loop structure during splicing process (when the 5' end of the intron attaches to the branch site)

lariat

The Shine-Dalgarno box is a short sequence in the ______ which provides a location for the binding of ______.

mRNA of bacteria, ribosomes

This type of mutation involves a change from a normal codon to a stop codon

nonsense mutation

Alternative splicing allows _____.

one gene to produce several different polypeptides

A mutation that changes the nucleotide sequence of the __________ , so that the repressor is no longer able to bind to the site, will cause a constitutive synthesis of the lactose-utilizing proteins.

operator

Which of the following are regulatory DNA elements of the lac operon?

operator, promoter

group of two or more genes under the transcriptional control of a single promoter

operon

The joining of two adjacent amino acids in the ribosome is achieved by the enzyme ________. (catalyzes the formation of polypeptide bonds)

peptidyl transferase

Lactose is transported through the membrane of the bacterial cell via an opening formed by the protein Lac __________ .

permease

The 3' end of eukaryotic mRNA, consisting of 100-200 A residues, that stabilizes the mRNA and increases the efficiency of translation initiation

poly-A tail

A single mRNA that contains the coding information for several distinct polypeptides is ____________ .

polycistronic

a messenger RNA transcript that has many bound ribosomes in the act of translation

polyribosome

In ______ cells, the initiator tRNA carries the amino acid N-formylmethionine.

prokaryotic

Each ribosomal subunit is assembled from ribosomal RNA and many different _______.

proteins

Crystallization studies have shown that the components located on the outer surface of a ribosome and on the periphery of the interface between the ribosomal subunits are the ribosomal __________, while the central part is __________.

proteins, RNA

To decipher the genetic code, an in vitro translation system containing cellular extracts with ribosomes, tRNA's, enzymes, and radioactive amino acids was used to synthesize ________________ from ______________.

radioactively labeled polypeptides, synthetic messenger RNAs

During termination of translation in bacteria, a stop codon is recognized by a(n) ___________.

release factor

In prokaryotic transcription, the switch from initiation to elongation involves ______.

release of sigma factor

In order to switch from initiation to elongation, RNA polymerase must ______.

release the sigma factor and move away from the promoter

Anabolic pathways are usually affected by ______ regulation, while ______ regulation usually affects catabolic pathways.

repressible; inducible

There are two transcription termination signals in prokaryotes, which are differentiated based on their requirement for a protein factor called _____.

rho

In _____________ transcription termination, a sequence of bases in the RNA forms a hairpin loop that serves as the signal for the dissociation of the RNA polymerase from the DNA and the release of the completed RNA.

rho-independent

Which components are assembled into the subunits of a ribosome?

ribosomal proteins, ribosomal RNA

To initiate translation, ribosomes attach to the mRNA at a site called the _______________ site. (upstream at the 5' end)

ribosome binding

In prokaryotes, the RNA polymerase holoenzyme is composed of the core enzyme plus the ______________.

sigma subunit

A snRNP consists of ____________ and _______________.

small nuclear RNAs, proteins

RNA splicing requires the aid of a multicomponent structure called the ____________.

spliceosome

The process that removes introns from a primary transcript and joins together successive exons is called RNA __________.

splicing

In prokaryotic cells, a transfer RNA carrying N-formylmethionine recognizes the ______ and is the first tRNA to bind to the ribosomal subunits, so it is called the initiator tRNA.

start codon

A series of three nucleotide bases that signals the end of a polypeptide chain is a(n)

stop codon

The ________________mutations in the lacI gene render the protein product incapable of binding the inducer.

superrepressor

Nirenberg and Leder were able to determine the particular amino acids specified by most codons in an experiment where a three-nucleotide mRNA molecule caused a ribosome to bind the __________carrying the corresponding amino acid.

tRNA

The adapter molecule that allows the codon of mRNA to specify the correct amino acid

tRNA

Which of the following is used in prokaryotic translation but not in eukaryotic translation?

tRNAifMet as the initiator tRNA, Coupling of transcription and translation, Shine-Dalgarno sequence, to facilitate mRNA binding to the small ribosomal subunit

The base sequence of the RNA transcript is complementary to the ________ strand of DNA.

template

Nirenberg and Leder added synthetic CUC and radioactive leucine to an in vitro translation system that included tRNAs and aminoacyl-tRNA synthetases, They subsequently filtered the ribosomes from the mixture, and all of the radioactivity was found on the filter with the ribosomes. This result indicated that ______.

the codon CUC is translated as leucine

Immediately after initiation of translation, what is located at the P site of an assembled ribosome?

the initiating tRNA

During translation, transfer RNAs bind to ______ specific regions on the ribosome, called the ______.

three; P, A and E sites.

the process of synthesizing RNA from a DNA template

transcription

The protein Lac permease is required for _______.

transporting lactose into the bacterial cell