CH 14 Genetics
Place the steps of mRNA capping in order, starting with the earliest on top.
1. RNA 5'-triphosphatase 2. Guanyltransferase 3. Methyltransferase
The following are steps involved in the formation of the open complex in eukaryotic transcription. List them in order, starting with the first on top.
1. TFIID binds to the TATA box 2. TFIIB binds to TFIID 3. RNA polymerase II binds to the core promoter 4. TFIIF is bound to RNA polymerase II 5. TFIIH and TFIIE bind to RNA polymerase II 6. TFIIH acts as a helicase to form an open complex
The following are steps involved in the processing of a precursor tRNA molecule in E. coli. Place them in the proper order, starting with the earliest on top.
1. The precursor tRNA is cut by the endonuclease RNaseP, which produces the correct 5' end of the mature RNA 2. An endonuclease removes a 170-nucleotide segment from the 3' end of the molecule 3. The exonuclease RNaseD binds to the 3' end and digests the RNA in the 3' to 5' direction. 4. Certain bases are covalently modified to allow for the tRNA to be properly functional
In humans, the long 45S rRNA transcript is cleaved to produce which of the following?
18S, 5.8S, and 28S
In eukaryotes, the protein complex called mediator facilitates the interaction between
RNA polymerase II and regulatory transcription factors that bind to enhancers and silencers.
The promoter shown in this diagram is recognized by
RNA polymerase II of eukaryotes.
What three categories of proteins are needed for basal transcription of protein-encoding genes in eukaryotes?
RNA polymerase II, general transcription factors, and a complex called mediator
A structural gene encodes a(n)
polypeptide
The first transcript produced from protein-encoding genes of eukaryotes is a long molecule called ___-mRNA
pre
In a gene, the DNA is transcribed into RNA from the
promoter to the terminator.
The sequence of a gene's DNA that is transcribed starts from the ___ and extends to the ___
promoter; terminator
Structural genes are also known as ___ encoding genes
protein
The nucleolus in eukaryotes is the site of processing of
ribosomal RNA
In bacteria, a short sequence in the mRNA provides a location that recruits the machinery to start translation. This sequence is called the ___-___ site.
ribosome-binding
An RNA molecule that has catalytic activity is called a(n)
ribozyme
The process by which the nucleotide sequence of a mRNA molecule is changed after it has been transcribed is called
rna editing
While RNA polymerase is sliding down the template, a small region of the protein termed the ______ separates the RNA-DNA hybrid.
rudder
Splicing that does not require the aid of other catalysts is known as ___-splicing
self
The removal of introns where RNA functions as its own ribozyme is a process called
self-splicing
Group II introns undergo a ______ process that is initiated by a(n) ______.
self-splicing ; adenine found within the intron
Group I introns undergo a ______ process that is initiated by a(n) ______.
self-splicing ; free guanine outside the intron
Regulatory elements that inhibit transcription are termed
silencers
Pre-mRNA splicing requires the aid of a complex called the
spliceosome
The end of protein synthesis is specified by a ___ ___ , which is a triplet of nucleotides in the mRNA molecule.
stop codon
This figure shows the promoter of a
structural gene of eukaryotes.
An exonuclease binds to the 5' end of the RNA that is being transcribed and degrades it in the 5' to 3' direction. The exonuclease then catches up to RNA polymerase II and causes termination. This describes the ___ model of transcription termination in eukaryotes.
torpedo
A protein that can diffuse into the cell nucleus and bind to its appropriate regulatory DNA element is called a
trans-acting factor.
The synthesis of an RNA molecule from a DNA template is called
transcription
The capping of a mature mRNA is a three-step process: (1) the enzyme RNA 5'- ___ removes a phosphate; (2) the enzyme ___ attaches guanosine monophosphate (GMP) to the 5' end; and (3) the enzyme ___ attaches a methyl group to a nitrogen at position 7 in the guanine base.
triphosphatase; guanylyltransferase; methyltransferase
The process of RNA splicing joins together
two exons
The following are steps in the splicing of pre-mRNA via a spliceosome. Put them in order, starting with the first on top.
1. U1 snRNP binds to 5' splice site, and U2 snRNP binds to braanch site 2. U4/U6 and U5 snRNP trimer binds 3. Intron loops out and exons are brought closer together. 4. 5' splice site is cut, and a lariat is formed 5. 3' splice site is cut, and the two adjacent exons are connected
The TATA box of eukaryotic genes is usually located about ______ from the transcriptional start site.
25 bp upstream
This figure depicts the
3' polyadenylation signal sequence.
Which of the following panels depict self-splicing introns?
A and B
What is a spliceosome?
A complex that removes introns found in pre-mRNA
What is the core promoter?
A relatively short DNA sequence that is necessary for transcription to take place
What is a promoter?
A specific target sequence to which RNA polymerase binds.
Which of the following can account for multiple transcripts from the same pre-mRNA?
Alternative splicing
Which of the following is the very first step in the formation of the preinitiation complex in eukaryotic transcription?
Binding of TFIID to the TATA box
The phenomenon whereby different combinations of exons are joined to produce different mRNAs from the same transcript is called ___ ___ (or exon shuffling)
Blank 1: alternative, alternative splicing, or alternate Blank 2: splicing
What are snRNPs?
Components of the spliceosome. The spliceosome consists of four subunits known as small nuclear ribonucleoproteins or snRNPs
Regulatory elements are short stretches of ______ involved in the regulation of ______.
DNA ; transcription
The terminator is a
DNA sequence that specifies the end of transcription.
Transcription factors are proteins that bind to
DNA sequences and control the rate of transcription.
The central dogma of genetics can be summed up by which of the following?
DNA → mRNA → polypeptide
What are the two types of regulatory elements that influence the rate of transcription in eukaryotes?
Enhancers and silencers
Which of the following are functions of the 7-methylguanosine cap of eukaryotic mRNAs?
Exit of most mRNAs from the nucleus into the cytoplasm Efficient splicing of introns, particularly the most 5' intron Recognition of the transcript by translation initiation factors
Which of the following are self-splicing introns that occur in the rRNA genes of the protist Tetrahymena?
Group I introns
In mammals, the ribosomal RNA gene is transcribed by RNA polymerase ___ to make a long primary transcript known as ___ rRNA. This transcript is then cleaved into ___ smaller fragments.
I; 45S; 3
In eukaryotic protein-encoding genes, three categories of proteins are required for basal transcription at the core promoter: RNA polymerase ___, general transcription ___, and a complex called mediator
II; factors
Which of the following statements about the catalytic site of RNA polymerase is true?
It contains Mg2+ and attaches nucleotides covalently to the 3' end of the transcript
Which of the following statements about the polyA tail of eukaryotic mRNA are TRUE?
It helps contribute to the stability of the mRNA. It is important for the exit of the mRNA from the nucleus. It is important for the synthesis of polypeptides from the mRNA.
What is the biological advantage of alternative splicing?
Multiple proteins can be derived from a single gene
A small nuclear ribonucleoprotein (snRNP) consists of small ___ ___ and proteins
Nuclear RNA
Which of the following statements about splicing in eukaryotes is true?
Pre-mRNA splicing is a widespread phenomenon, whereas self-splicing is relatively uncommon.
Transcription is the process of synthesizing
RNA from a DNA template.
A ribozyme is a(n)
RNA molecule with catalytic activity.
Which of the following statements about eukaryotic RNA polymerases is true?
RNA pol I transcribes most rRNAs; RNA pol II transcribes all mRNAs; RNA pol III transcribes all tRNAs
Sidney Altman and his colleagues discovered that the RNA subunit of which enzyme(s) had catalytic activity?
RNaseP
Which component involved in processing of tRNAs is a ribozyme?
RNaseP
In E. coli, tRNAs are synthesized as large precursor tRNAs that must be cleaved to produce mature, functional tRNAs that carry amino acids. The processing of precursor tRNA molecules typically involves an endonuclease called ______, and an exonuclease called ______.
RNaseP ; RNaseD
The 7-methylguanosine cap of eukaryotic mRNAs serves which of the following functions?
Recognition of the 5' end of the transcript by the translation machinery
What are silencers?
Regulatory elements in eukaryotes that inhibit transcription
What are enhancers?
Regulatory elements in eukaryotes that stimulate transcription
The core promoter typically consists of a TATAAA sequence called the ___ box and the transcriptional start site.
TATA
Which of the following is an example of a cis-acting element in eukaryotic transcription?
TATA box, enhancer, silencer
During the formation of the open complex in eukaryotic transcription, ______ acts as a helicase and first denatures the DNA at the ______.
TFIIH ; TATA box
Which of the following best defines a pre-mRNA?
The mRNA of eukaryotes that is produced in the nucleus and has yet to be processed
Transcription factors that bind to regulatory DNA elements are called ______-______ factors because they are encoded by genes that may be on a different chromosome from the genes they control.
Trans-acting
True or false: In complex eukaryotes, pre-mRNA splicing is much more common than self-splicing.
True. In complex eukaryotes, self-splicing (which involves group I and group II introns) is relatively uncommon.
All of the following statements about the splicing of pre-mRNA via a spliceosome are true except one. Which one?
U1 snRNP binds to the 3' splice site
The capping of a mature mRNA is an event that involves the addition of
a 7-methylguanosine to its 5' end.
The mechanism of self-splicing of group II introns is similar to that of group I introns. The main difference is that a 2'-OH group on a(n) ___ nucleotide within the intron begins the catalytic process.
adenine
The "tail" of a eukaryotic mRNA refers to a string of _______ nucleotides added to the _______ end.
adenine; 3'
After RNA polymerase II transcribes the polyadenylation signal, it is destabilized and dissociates from the DNA. This describes the ___ model of transcription termination in eukaryotes.
allosteric
General transcription factors are those that
are always needed for RNA pol II to initiate transcription.
The low level of transcription caused by the presence of the core promoter by itself is known as ___ transcription
basal
The addition of a 7-methylguanosine to the 5' end of a mature mRNA is a process known as
capping
What process is shown in this diagram?
capping
Alternative splicing allows an organism to
carry fewer genes in its genome.
DNA sequences that exert their effects only over a particular gene on the same chromosome are called ___-___ elements
cis-acting
The preinitiation complex is a(n) ______ complex that consists of RNA polymerase II and five general transcription factors.
closed
The mRNA contains groups of three nucleotides that specify the amino acid sequence of a polypeptide. These three-nucleotide groups are called
codons
Short stretches of DNA that are involved in the regulation of transcription are known as regulatory sequences or regulatory
elements
An enzyme that cleaves a covalent bond between two adjacent nucleotides within a strand is called a(n)
endonuclease
Maturases are proteins that
enhance the rate of splicing of group I and group II introns.
Regulatory elements that stimulate transcription are termed
enhancers
Sequences in DNA that are present in mature mRNA and which code for polypeptides are called
exon
An enzyme that cleaves a covalent bond between two nucleotides at one end of a strand is called a(n)
exonuclease
The overall process by which the information within a gene is used to produce a functional product is called ___ ___
gene expression
For eukaryotic protein-encoding genes, the five proteins that are always needed for RNA polymerase II to initiate RNA synthesis are called ___ ___ factors
general transcription
The product of this reaction is the nucleotide
hypoxanthine
Noncoding sequences that are initially transcribed into mRNA are termed
introns
Sequences that are found between exons are called
introns
The product of a protein-encoding gene is a(n) ______ molecule.
mRNA
The ribosome-binding site is a sequence in bacterial ______ that is involved in ______.
mRNA; translation initiation
In a living cell, the rate of self-splicing of group I and group II introns is enhanced by proteins known as
maturases
In prokaryotes, a protein-encoding gene is transcribed into an RNA molecule called ___ RNA
messenger
In eukaryotes, the assembly of ribosomal subunits occurs in a site within the nucleus called the
nucleolus
The enzymatic addition of about 250 adenine nucleotides to the mRNA after it is transcribed is a process called
polyadenylation or 3' end polyadenylation