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What functions as an intermediary between DNA and protein synthesis?
RNA
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Name the three types of RNA discussed in class.
- messenger RNA (mRNA)
- transfer RNA (tRNA)
- ribosomal RNA (rRNA)
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What is the function of mRNA?
to carry the genetic message from the nucleus to the protein factory of the cell
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What is the function of tRNA?
to interpret mRNA and bring amino acids to the growing peptide chain
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Which type of RNA is most abundant?
ribosomal RNA
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The type of RNA that picks up amino acids, brings them to the ribosome, and adds them to the growing protein is:
transport RNA
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The RNA that is a recipe for protein is:
messenger RNA
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What occurs during transcription?
DNA is used as a template to make mRNA
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What occurs during translation?
mRNA is decoded to form amino acid chains (proteins)
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What are the two properties of our genetic code?
- the code must be unambiguous
- the code must be redundant
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Three base pairs on a strand of mRNA are known as a:
codon
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A codon corresponds to what?
an amino acid
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The fact that each codon only codes for one amino acid is an example of how our genetic code is:
unambiguous
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The fact that several codons can correspond to a single amino acid is an example of how our genetic code is:
redundant
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True or False - Some codons act as signals.
True
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What two things does the codon AUG code for?
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UAA, UAG, and UGA all code for:
stop
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Where does transcription occur?
in the nucleus
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What role does the promoter region play in transcription?
it initiates transcription
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The point of transcription intiation is known as the:
TATA box
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The TATA box is part of the:
promoter region
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The TATA box is recognized by:
transcription factors
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Transcription factors bind to the DNA strand at the TATA box and help what other enzyme bind to the DNA strand?
RNA polymerase II
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What is the function of RNA polymerase II?
to pull apart the DNA strand and add RNA complimentary base pairs
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Which strand of parent DNA is the template for transcription?
the 3' to 5' strand
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In which direction does RNA form?
5' to 3'
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True or False - After the RNA strand forms, the DNA strands will reform a double helix.
True
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Why does transcription stop in bacteria?
a terminator causes the RNA to detach from the template strand
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Why does transcription stop in eukaryotes?
RNA poly II transcribes the polyadenylation sequence
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AAUAAA codes for what?
the polyadenylation sequence
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After transcribing the polyadenylation sequence, 30 nucleotides later the mRNA is:
cut free
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True of False - Following the termination of transcription the resulting RNA leaves the nucleus for the ribosomes.
False - the pre-mRNA must first be processed
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What is added to the 5' prime end of pre-mRNA?
a modified guanine cap
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What is the function of the modified guanine cap added to pre-mRNA?
It is a signal site for ribosome binding
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What is added to the 3' end of pre-mRNA?
a poly-A tail
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What is a poly-A tail?
a chain of 150-200 adenines
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What is the function of the poly-A tail?
helps transport the mRNA out of the nucleus
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What is the structure of pre-mRNA?
sequence of nucleotides comprised of exons and introns
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Which codes for amino acids, exons or introns?
exons
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True or False - Introns code for specific amino acids.
False - introns don't code for anything
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The molecule that clips out the introns and splices together exons is:
spliceosome
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Spliceosomes are comprised of:
snRNA
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Which parts of pre-mRNA must be removed before it can be sent to the ribosomes, exons or introns?
introns
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Where does translation occur?
cytoplasm
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What shape is tRNA?
a cloverleaf
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What is the function of aminoacyl-tRNA Synthetase?
to attach the correct amino acid to a tRNA
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Aminoacyl-tRNA synthetase requires an amino acid and what molecule?
ATP
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How does tRNA bond to an amino acid?
covalently
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A tRNA molecule that is bound to an amino acid is known as:
aminoacyl tRNA
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How many amino acids do humans have in their body?
20
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How many types of aminoacyl-tRNA synthetase do humans have in their body?
20
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tRNA have three nucleotides that correspond to the three nucleotides of an mRNA codon called an:
anti-codon
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How many codon combinations are there?
64
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How many types of tRNA are there?
45
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True or False - Some tRNA molecules can bind with more than one codon.
True
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The flexibility in the 3rd base pair that allows some tRNA to bind with multiple codons is known as:
wobble
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What role does the ribosome play in protein synthesis?
it is the site of protein synthesis or assembly
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Which subunit of a ribosome, small or large, has an mRNA binding site?
the small subunit
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Where does the small subunit bind with the mRNA?
just upstream of the start codon
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List the three sites on the large ribosomal subunit.
- the A site
- the P site
- the E site
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What is the function of the A site?
site where tRNA enters to add the next amino acid
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What is the function of the P site?
site that contains the tRNA with the growing protein chain
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What is the function of the E site?
tRNA exit site
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When the large subunit attaches to the small subunit it completes the:
translation initiation complex
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What binds to the start codon to begin translation?
a tRNA initiator
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What kind of bond links the amino acids within the developing protein?
a peptide bond
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When the amino acid from the tRNA is joined to the peptide chain, the amino acid chain is actually shifted from the ____ site to the ____ site.
P site to the A site
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When the stop codon is read, what enters the A site?
release factors
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What are the two primary functions of release factors?
- release protein chain from the tRNA
- break apart the ribosome
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Describe a silent mutation.
a mutation with no physiological effect on the individual
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A mutation with no visible effect on an organism is a/an:
silent mutation
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This type of mutation changes an entire amino acid.
missense mutation
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Describe a missense mutation.
a mutation that changes an entire amino acid
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What disease discussed in class is the result of a missense mutation?
sickle-cell anemia
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Describe a nonsense mutation.
occurs when an amino acid codon is replaced with a stop codon
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When an amino acid is replaced in the mRNA strand with a stop codon you have this type of mutation.
nonsense
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True or False - Insertions and deletions have minor effects on protein synthesis.
False - they have major effects
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Adding base pairs to an mRNA results in what type of mutation?
insertion
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Removing base pairs from an mRNA, and thus changing the entire codon sequence, is known as a _______ mutation.
deletion
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When protein synthesis is stopped prematurely, it is most likely due to a _________ mutation.
nonsense
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