Chapter 7: RNA and the Genetic Code Flashcards
DNA coding strand is identical to the ________.
mRNA
The DNA template strand is ________________ and ____________ to the mRNA.
complementary; antiparallel
____________ RNA carries information specifying the amino acid sequence of the protein to the ribosome.
messenger
mRNA may undergo a host of ________________ modifications prior to its release from the nucleus.
posttranscriptional
mRNA is transcribed from template DNA strands by ____ ____________ in the ________ of cells.
RNA polymerase; nucleus
mRNA is the only type of RNA that contains information that is translated into ________.
proteins
In eukaryotes, mRNA is ____________, meaning each mRNA molecule translates into only one protein product.
monocistronic
In prokaryotes, mRNA may be ____________, and starting the process of translation at different locations in the mRNA can result in different proteins.
polycistronic
____________ RNA is responsible for converting the language of nucleic acids to to the language of amino acids and peptides.
transfer
Each tRNA molecule contains a folded strand of RNA that includes a 3-nucleotide ____________.
anticodon
To become part of a nascent polypeptide in the ribosome, amino acids are connected to a specific tRNA molecule; such tRNA molecules are said to be ________ or ________ with an amino acid.
charged, actiavated
Each type of amino acid is activated by a different ____________-________ ____________ that requires 2 high-energy bonds from ____, implying that the attachment of the amino acid is an energy rich bond.
aminoacyl-tRNA synthetase; ATP
Aminoacyl-tRNA synthetase transfers the activated amino acid to the ____ end of the correct tRNA.
3’
Each tRNA has a ____ nucleotide sequence where the amino acid binds.
CCA
The high-energy aminoacyl-tRNA bond is used to supply the energy needed to create a ________ bond during translation.
peptide
____________ RNA is synthesized in the ________ and functions as an integral part of the ribosomal machinery used during protein assembly in the cytoplasm.
ribosomal; nucleolus
Many rRNA molecules function as ____________, that is, enzymes made of RNA molecules instead of peptides.
ribozymes
rRNA helps catalyze the formation of peptide bonds and is also important in splicing out its own ________ within the nucleus.
introns
Every preprocessed eukaryotic protein starts with the exact same amino acid: ________________.
methionine
The codon for methionine (____) is considered the ________ codon for tranlation of the mRNA into protein.
AUG; start
What are the 3 stop codons?
UAA, UGA, UAG
U Are Annoying, U Go Away, U Are Gone
The genetic code is ____________ because more than 1 codon can spcify a single amino acid.
degenerate
A ____________ mutation is where one amino acid substitutes for another.
missense
A ____________ mutation is where the codon now encodes for a premature stop codon.
nonsense
The creation of mRNA from DNA is ____________.
transcription
RNA polymerase locates genes by searching for specialized DNA regions known as ____________ regions.
promoter
In eukaryotes, ____ ____________ ____ is the main player in transcribing mRNA, and its binding site in the promoter region is known as the ________ ____.
RNA polymerase II; TATA box
____________ ________ help RNA polymerase locate and bind to this promoter region of the DNA, helping to establish where transcription will start.
Transcription factors
RNA polymerase does not require a ________ to gstart generating a transcript.
primer
RNA polymerase I is located in the ____________ and synthesizes ________.
nucleolus; rRNA
RNA polymerase III is located in the nucleus and synthesizes ________ and some ________.
tRNA and some rRNA
Does RNA polymerase proofread?
No!
RNA polymerase travels along the ____________ strand, and RNA is thus identical to the ________________ strand.
template, coding
The first base transcribed from DNA to RNA is defined as the ____ base of that gene region.
+1
Bases to the left of the first transcribed base (+1) are known as being ____________ and are given ____________ numbers.
upstream; negative
Bases to the right of the first transcribed base are ____________ and are given ____________ numbers.
downstream; positive
The TATA box usually falls around position ____.
-25
After a stop sequence is reached, transcription is terminated, the DNA helix reforms, and the primary transcript formed is termed ________________ ____________ RNA (hnRNA).
heterogeneous nuclear
Before hnRNA can leave the nucleus to be translated, it must undergo what 3 processes?
- intron/exon splicing
- addition of 5’ cap
- addition of 3’ poly-A tail
Splicing removes noncoding sequences called ____________ and ligates coding sequences called ____________.
introns, exons
Splicing is accomplished by the ________________.
spliceosome
In the spliceosome, ________ ________ RNA molecules couple with proteins known as ________ ________ ________________.
small nuclear; small nuclear ribonucleoproteins
At the 5’ end of the hnRNA molecule, a ____ is added during transcription. What does this do?
cap; it is recognized by the ribosome as the binding site and protects the mRNA from degrading in the cytoplasm
A ________-____ tail is added to the ____ end of the mRNA transcript and protects the message against rapid degrdation.
poly-A, 3’
As soon as the mRNA leaves the nucleus, it will start to ________ from the 3’ end. The longer the poly-A tail, the longer the mRNA can survive before this happens.
degrade
When only exons remain and the cap and tail have been added, the cell has created the ________ mRNA.
mature
____________ regions of the MRNA will still exist at the 5’ and 3’ edges of the transcript because the ribosome initiates translation at the start codon and will end at a s top codon.
untranslated
For some genes, the primary transcript can be spliced together in different ways to produce different protein variants. This is called ____________ ____________.
alternative splicing
Once the mRNA transcript exits into the cytoplasm, it begins ____________.
translation
The ____________ is composed of proteins and rRNA. It brings the mRNA message together with the charged aminoacyl-tRNA complex to generate the protein.
ribosome
What are the 3 stages of translation?
- initiation
- elongation
- termination
In prokaryotes, the small ribosomal unit binds to the ________-____________ sequence in the 5’ ________________ region of the mRNA.
Shine-Dalgarno; untranslated
In eukaryotes, the small subunit binds to the ____ ____ structure.
5’ cap
The charged ________ ________ binds to the AUG ________ ________ through base-pairing with its anti-codon within the P site of the ribosome.
initiator tRNA, start codon
After the small subunit binds, the ________ subunit then binds, forming the completed initiation complex. This is assisted by ____________ ________ that are not permanently associated with the ribosome.
large; initiation factors
What are the 3 main binding sites of ribosomes?
- A site
- P site
- E site
The A site holds the incoming ____________-________ complex.
aminoacyl-tRNA
What determines the A site?
the mRNA codon
The P site holds the ________ that carries the growing polypeptide chain. A ____________ bond is formed as the polypeptide is passed from the tRNA in the P site to the tRNA in the A site.
tRNA; peptide
This requires ____________ ____________, an enzyme that is part of the large subunit.
peptidyl transferase
____ is used for energy during the formation of peptide bonds.
GTP
The E site is where the now inactivated ________ pauses transiently before exiting the ribosome.
tRNA
As the now-uncharged tRNA enters the E site, it quickly ________ from the mRNA and is ready to be recharged.
unbinds
____________ ________ assist by locating and recruiting aminoacyl-tRNA along with ____, while helping to remove ____ once the energy has been used.
elongation factors; GTP, GDP
When any of the three stop codons moves into the A site, a protein called ________ ________ binds to the termination codon, causing a water molecule to be added to the polypeptide chain.
release factor
The addition of a water molecule to the polypeptide chain allows ________ ____________ and ____________ ____________ to hydrolyze the completed polypeptide chain from the final tRNA.
peptidyl transferase; termination factors
A specialized class of proteins called ____________ assist in the protein-folding process.
chaperones
____________ is the addition of a phosphate group by protein ________ to activate or deactivate proteins.
phosphorylation; kinase
Phosphorylation in eukaryotes is most commonly seen with which 3 amino acids?
- serine
- threonine
- tyrosine
____________ is the addition of carboxylic acid groups, usually to serve as ________-binding sites.
carboxylation; calcium
________________ is the addition of oligosaccharides as proteins pass through the ____ and ________ ________ to determine cellular destination.
glycosylation; ER, Golgi apparatus
____________ is the addition of lipid groups to certain membrane-bound enzymes.
prenylation
This type of structure is called an ____________ - a cluster of genes transcribed as a single mRNA.
operon
The ____________ gene codes for the protein of interest.
structural
Upstream of the structural gene is the ____________ site, a nontranscribable region of DNA that is capable of binding a ________ protein.
operator; repressor
Further upstream is the ____________ site, which is similar in function to promoters in eukaryotes; it provides a place for ________ ____________ to bind.
promoter; RNA polymerase
Further upstream is the ____________ gene, which codes for a protein known as the ____________.
regulator; repressor
In ____________ systems, the repressor is bonded tightly to the operator system and thereby acts as a roadblock. RNA polymerase is unable to get from the promoter to the structural gene because the ________ is in the way.
inducible; repressor
____________ systems allow constant production of a protein product.
repressible
In contrast to the inducible system, the repressor made by the ____________ gene is inactive until it binds to a ____________.
regulator; corepressor
____________ ________ are transcription-activating proteins that search the DNA looking for specific DNA-binding motifs.
Transcription factors
The ____-________ domain binds to a specific nucleotide sequence in the promoter region or to a DNA ____________ ____________.
DNA-binding; response element
The ____________ ________ allows for the binding of several transcription factors and other important regulatory proteins.
activation domain
Several response elemnts may be grouped together to form an ____________, which allows for the control of one gene’s expression by multiple signals.
enhancer
________________ is tightly coiled DNA that appears dark under the microscope. It is ____________.
heterochromatin; inactive
____________, on the other hand, is looser and appears light. These genes are ________.
euchromatin; active
________ ____________ are involved in chromatin remodeling and acetylate lysine residues found in the ________ terminal tail regions of histone proteins.
histone acetylases
____________ of histone proteins decreases the positive charge on lysine residues and weakens the interaction of the ________ with DNA, resulting in an open ____________ conformation that allows easy access.
acetylation; histone; chromatin
____________ ____________ are proteins that function to remove acetyl groups from histones, which results in a closed chromatin conformation.
histone deacetylases
____ ____________ is also involved in chromatin remodeling and regulation of gene expression levels. Methylation is often linked with ____________ of gene expression.
DNA metyhlation; silencing
