Biology chapter 12
Which of the following are controls of eukaryotic gene expression that regulate whether transcription can occur? Select all that apply.
- modification of chromatin structure - availability of different types of transcription factors
Select all of the methods of post-transcriptional control in eukaryotic gene expression.
- modification of the protein - availability of different types of RNA
Select all the effects on the lac operon if allolactose binds to the repressor
- the repressor will not bind to the operator - genes for breaking down lactose will be transcribed
Put the following steps in the order that they occur during the beginning of translation
-mRNA binds to the small ribosomal subunit -the larger ribosomal subunit binds to form a complete ribosome -the initial tRNA binds to the AUG start codon on the mRna at the P site -the second tRNA binds to the codon at the A site -the ribosome begins to move three nucleotides at a time down the mRNA
About _____ of the human genome consists of exons, while ________ of the genome consists of introns
1%; 24%
Put the following steps in the order that they occur during gene silencing
1. Certain RNA sequences form hairpin loops consisting of double-stranded RNA 2. Dicer recognizes and cuts double-stranded RNA, forming siRNA 3. siRNA and protein assemble into the RISC complex 4. RISC unwinds siRNA, forming single-stranded siRNA 5. siRNA is able to bind to mRNA with a complementary sequence
Place these steps in the correct order that they occur in eukaryotic protein synthesis
1. DNA is transcribed into mRNA 2. Introns are removed and exons are joined together 3. The transcript leaves the nucleus 4. The transcript binds to the ribosome 5. mRNA is translated into a polypeptide 6. The completed polypeptide is released
Put the steps of translation into their correct order
1. The small ribosomal subunit binds to mRNA, and the larger ribosomal subunit binds to form a complete ribosome 2. A tRNA binds to the A site carrying an amino acid 3. The ribosome moves three nucleotides to the right, and the amino acid from the A site is transferred to the growing polypeptide chain at the P site 4. The tRNA in the E site exits from the ribosome
Place in order the steps of translation
1. rRNA within a ribosome binds to mRNA 2. the ribosome moves along the mRNA 3. amino acids are added to a growing polypeptide chain 4. the ribosome encounters a "stop" signal 5. the ribosome disengages from the mRNA 6. the ribosome releases the polypeptide
About how much of the human genome consists of introns
24%
When making an mRNA transcript, RNA polymerase moves from
5' to 3' adding RNA nucleotides to the 3' end
Transfer RNA carrying an amino acid binds to a ribosome at the _______
A site
The promoter is a region of the _______ where RNA polymerase binds to initiate transcription
DNA
How does mRNA help protect the information contained in DNA?
The mRNA is made in the nucleus using DNA and then goes out into the cell to serve as an expendable copy
An enhancer is
a binding site for eukaryotic activators that is distant from the promoter
Activating enzymes match the correct _________
amino acid to its tRNA
The ________ is a three-nucleotide sequence on a tRNA molecule that is complementary to an mRNA codon
anticodon
What did biologists use to help them determine which amino acid matched to a codon?
artificial mRNA trial and error
Match each process with its key starting materials
DNA replication: DNA polymerase, DNA, ligase, helicase Transcription: RNA polymerase, DNA Translation: ribosome, mRNA, tRNA, amino acids
Match each process to its end product
DNA replication: two copies of DNA Transcription: mRNA Translation: polypeptide
Select modifications made to the primary RNA transcript in eukaryotes that protect the RNA from degradation
- Addition of a 5' cap - Addition of a poly-A tail
Select the correct statements about the process of translation
- At translation initiation, mRNA binds to the small subunit of a ribosome, and then the large subunit binds to form a complete ribosome. - The ribosome moves down the mRNA three nucleotides at a time. - The sequence of the mRNA determines what tRNAs will bind, and what amino acids will be added to the polypeptide. - The tRNA bound at the P site moves to the E site as the ribosome moves to the next codon.
Select all of the reasons why the presence of lactose and absence of glucose allows transcription of the lac operon
- CAP is able to bind to cAMP - cAMP is present at low concentration of glucose - Allolactose binds to the repressor
Select all of the following that are true about transfer RNA (tRNA)
- Contains an anticodon on one of its loops - Has an amino acid attachment site at its 3' end - Has a folded, three-loop structure
Select the following that are true about transcription
- Information is transferred from DNA to RNA - An mRNA copy of the DNA is produced - It is the first stage of gene expression
Select components that can be involved in the eukaryotic transcription complex
- RNA polymerase - activators - basal transcription factors - coactivators
When a stop codon is encountered during translation of a protein, which of the following occur?
- The newly synthesized polypeptide is released - The ribosome complex disassembles
Select molecules that must be present for the initiation complex of transcription to form in eukaryotic cells
- basal transcription factors - RNA polymerase
Repressors can be removed from the operator in prokaryotic cells by which of the following?
- change in shape of the repressor that causes it to detach from the DNA - attachment of a special signal molecule
Select results of the addition of methyl and acetyl groups to histones during epigenetic modification
- chromatin structure is disrupted - DNA is more accessible for transcription
Select all of the following that modify the rate of transcription in eukaryotes
- coactivators - activators - mediators
Select all of the following that describe genes in eukaryotes
- contain sections called exons that encode polypeptides - have interrupting segments called introns
Select the two ways that siRNAs can achieve gene silencing.
- destroying the mRNA that has the complementary sequence - binding to mRNA molecules with a complementary sequence, blocking translation
Controls of eukaryotic gene expression that act on mRNA after it is produced include which of the following? Select all that apply.
- gene splicing - alternative splicing
Modifications to what components of chromosomes can affect the accessibility of genes to RNA polymerase?
- histones - DNA bases
Select all of the following that are true about regulation of the lac operon
- in the absence of glucose and the presence of lactose, CAP/cAMP binds and transcription occurs - when lactose is present and glucose absent, the repressor is removed - in the absence of lactose, a repressor blocks the promoter region
Select all of the controls of eukaryotic gene expression that occur before transcription
- initiation of transcription - epigenetic modification
In eukaryotes, basal transcriptions factors help recruit ______ to the promoter to form the _______ complex and allow transcription to occur at a basal rate
RNA polymerase; initiation
Controlling whether ______ is able to bind to the _______ will affect the initiation of gene transcription in prokaryotes
RNA polymerase; promoter
The promoter region on the DNA is the site where _______ binds to initiate _________
RNA polymerase; transcription
Why is the process of creating a protein from mRNA called translation?
The chemical language changes from the nucleotides of RNA to amino acids in the protein
In prokaryotic DNA, a site called the operator _________
binds the repressor
The correct amino acid is added to a growing polypeptide when an anticodon on the tRNA ______
binds to a matching codon on the mRNA
To begin transcription, RNA polymerase
binds to one strand of the DNA double helix that contains a promoter-site sequence in recognizes
In RNA processing, ____ are removed from the primary RNA transcript to form the _______
introns; mature mRNA
In eukaryotic gene transcription, a(n) ________ is the binding site for activators and is located _______ the promoter
enhancer; distant from
In eukaryotes, transcription can be increased when activators bind to _______ and interact with the __________
enhancers; initiation complex
Alterations to DNA or histones that affect gene expression but do not alter the sequence of DNA nucleotides are called
epigenetic modification
_______ are the sections of DNA that encode the amino acid sequence of a polypeptide, whereas ______ are noncoding sections of DNA that must be removed during processing of the mRNA transcript
exons; introns
A __ is a short segment of DNA that encodes for a specific protein
gene
The use of information contained in DNA to direct the production of specific proteins is known as __________
gene expression
The information specifying hereditary traits is encoded in blocks of DNA called
genes
The information specifying heredity traits is encoded in blocks of DNA called
genes
What statement characterizes gene regulation in multicellular organisms
genes are transcribed at the right time during development in a prescribed order
What is the result of DNA methylation during epigenetic modification
genes are turned off
The __ code refers to the three nucleotide sequences present on mRNA, called codons, which code for specific amino acids to be added to the polypeptide chain.
genetic code
At its lowest level chromosomes are organized into nucleosomes made up of _________
histones, DNA
A primary transcript of mRNA ______
includes both exons and introns
Specific transcription factors can bind to the initiation complex to _______
increase the level of gene transcription
Prokaryotic cells respond to the environment by _______
increasing or decreasing enzyme levels
In eukaryotes, transcription factors are proteins that
interact with RNA polymerase
Sections of a eukaryotic gene that do not encode polypeptides and that are removed during RNA processing are called _________
introns
In eukaryotes, why do primary RNA transcripts have to be processed to form mature mRNA transcripts
introns have to be removed before translation
The subunits of a ribosome _________
nest together to form a functional unit
The regulation of gene expression ensures that
not all genes are expressed at all times
During translation the sequence of ______ is translated into a sequence of _______
nucleotides; amino acids
control of gene expression in prokaryotes is designed to produce _________
only the proteins needed based on environmental conditions
A repressor stops transcription in prokaryotic cells by _______
preventing the binding of RNA polymerase to the promoter
The unprocessed mRNA transcript is called a ______ transcript
primary RNA
In a _______ cell, a gene can be translated as it is being transcribed
prokaryotic
Gene expression in prokaryotes can be controlled by allowing access or blocking access of RNA polymerase to the _____
promoter
Starting at the ________ located at the beginning of a gene, RNA polymerase synthesizes __________
promoter; an mRNA transcript of the DNA
In what cellular process are messenger RNA, transfer RNA, ribosomal RNA, and silencing RNA used?
protein synthesis
The components of ribosomes are
proteins and rRNA
A region of ________ found in the small subunit of the ribosome corresponds to the leader region of all genes and causes the _______ to bind correctly to the ribosome during initiation of translation
rRNA; mRNA
What type of chemical modification of histones can block transcription by causing the DNA to condense further
removal of methyl groups
The attachment of a special signal molecule to the repressor can _______
remove the repressor from the DNA
ribosomes are composed of proteins and __ RNA
ribosomal
The site of protein synthesis is the
ribosome
The binding of _______ to mRNA molecules with a complementary sequence blocks translation and silences the gene
siRNA
What type of RNA can regulate gene expression by preventing translation
small interfering RNA
What can bind to the initiation complex to achieve more regulation of transcription
specific transcription factors
A ribosome functions in the
synthesis of proteins
The three sites on the ribosome that form dents or pockets are the sites where ________ binds.
tRNA
During transcription, RNA polymerase binds to one strand of DNA, which is called the _______ strand, and adds complementary nucleotides to the DNA, using _______ instead of thymine
template, uracil
How are activators able to interact with the initiation complex even though they bind to distant enhancer sites
the DNA bends, bringing the activator into contact with the initiation complex
what is the same in practically all organisms
the genetic code
Precise control of the level of transcription in eukaryotes is achieved by the formation of a
transcription complex
In eukaryotes, transcription is more complex and requires not only RNA polymerase but also ________ that interact with RNA polymerase
transcription factors
During translation _________ RNA (tRNA) is responsible for bringing the amino acids to the ribosome to be added to the polypeptide chain
transfer
In a process called __________, the order of nucleotides in mRNA is used to direct the synthesis of a polypeptide
translation
Most organisms use the same genetic code
true
Prokaryotes control gene expression mainly by ________
turning transcription of genes on or off
How many subunits make up a ribosome
two
Match the correct site on the ribosome to its function
A site: Site where incoming tRNAs with bound amino acids enter the ribosome P site: The site where peptide bonds form between the incoming amino acid and the growing peptide chain E site: The site where tRNAs are released from the mRNA
What complex acts as an activator at the lac operon
CAP/cAMP
According to the _____________ in all organisms the information in the DNA passes to an RNA copy, which then directs the synthesis of a protein
Central Dogma
Select the correct statement about genes in prokaryotic and eukaryotic cells
In prokaryotic cells, genes occur as unbroken sections of DNA, while in eukaryotic cells, genes have interrupting segments called introns
In gene expression, ________
Information in DNA directs the synthesis of a specific polypeptide
The silencing of genes that are complementary to double-stranded RNA is called
RNA interference
In translation, a codon is
a group of three nucleotides that determine the amino acid to be added to a polypeptide
An activator in prokaryotic cell transcription is
a regulatory protein that binds to the DNA and makes the promoter more accessible to RNA polymerase
In a prokaryotic cell, an operon is _______
a section of DNA containing a cluster of genes that are transcribed together
How is the promoter of the lac operon made more accessible to RNA polymerase
a signal molecule binds to CAP, allowing CAP to bind to the DNA
In eukaryotes, coactivators and mediators act to
modulate the effect of specific transcription factors
The primary method of epigenetic modification is the
addition of a methyl group to cytosine nucleotides
The primary function of gene control in prokaryotes is to ___________
adjust the cell's activities to the environment
Small interfering RNAs regulate gene expression
after transcription
Alternative splicing of the exons of an RNA transcript _______
allows the production of different proteins from the same gene
The removal of introns in the primary mRNA transcript and the joining of the remaining exons in different ways is called ________
alternative splicing
Epigenetic modification refers to the
chemical alteration of DNA or histones that affect gene expression
What are polyribosomes
clusters of ribosomes translating an mRNA strand
The triplet of nucleotides in mRNA that determines the amino acid to be added to the polypeptide sequence is call an
codon
During translation the __ is used to direct the synthesis if the protein by providing the direction taken from the DNA
mRNA
When serving as an expendable copy of DNA, _______
mRNA leaves the nucleus to be used for protein synthesis
Chemical modifications that affect condensation of genetic material
make genes more or less accessible to RNA polymerase
What molecule brings the information from the DNA to the ribosomes for translation of the nucleotide sequence into the amino acid sequence of a polypeptide
messenger RNA
Why is the lac operon repressed
the repressor is bound to the operator
Given the following steps of translation, the formation of a peptide bond between an existing polypeptide and an amino acid forms right before __________
the tRNA in the P site moves to the E site
Why can transcription and translation take place at the same time in prokaryotes
there is no nuclear membrane to act as a barrier
In the genetic code, each sequence of __ nucleotides to a(n) __
three; amino acid
In the genetic code, each sequence of ______ nucleotides corresponds to a(n) _________
three; amino acid
Artificial mRNA consisting of repeating nucleotides, such as UUUUUUUUUUUUU, were used__
to determine which condons correspond to which acids
At what stage do prokaryotes control most of gene expression
transcription
