RNA and protein synthesis (complete) Flashcards
What are the Three main differences between DNA and RNA
- Bases (T in DNA, U in RNA)
- The 2nd carbon of the sugar (oxidated in RNA, Deoxidated in DNA)
- RNA is usually single stranded DNA is double stranded
What are the three types of RNA
- tRNA
- rRNA
- mRNA
How do you differentiate between template and non template strands
the template strand is the DNA strand that Actually has the new DNA/RNA strand base pairing to it for a moment.
How does the non-template strand of DNA compare to the DNA/RNA that is transcribed from it
it will be identical to the new daughter DNA strand (nearly identical to the new daughter RNA strand just with U and T switched)
What are the other names for the non-template strand
the gene
coding strand
sense strand
What are the other names of the template strand
non-coding strand
antisense strand
What is mRNA and what does it do
it is messenger RNA and it codes for specific amino acid sequences to be put together into proteins
What is a codon
a three base pair region on mRNA that codes for a specific amino acid
is prokaryotic mRNA poly or monocistronic
polycistronic (mRNA contains information for more than one polypeptide)
is eukaryotic mRNA poly or monocistronic
monocistronic (each mRNA strand only codes for one polypeptide)
What is tRNA and what does it do
Transfer RNA
it binds specific Amino acids, and recognizes proper mRNA codons to deliver the appropriate amino acid
What are the parts of tRNA
- Acceptor stem
2. anticodon looop
What does the acceptor stem of tRNA do
binds a specific amino acid
what does the anticodon loop of tRNA do
reads the codon of the mRNA, binds to it, delivering the appropriate amino acid in the sequence
What is rRNA and what does it do
ribosomal RNA
it makes up 65% of the ribosome, it is the catalytic region of the ribosome
Which types of RNA are read and used to create proteins
only mRNA
What is RNA transcription
Using a segment of DNA to create RNA
in which direction is RNA and DNA synthesized
the 5’ to 3’ direction
in which direction do the polymerases read the template strand
the 3’ to 5’ direction
do prokaryotic RNA polymerases require a primer
nope
do prokaryotic RNA polymerases have exonuclease activity (proofreading)
nope
how does RNA transcription in prokaryotes happen
- Sigma binds to the promotor region (-10, -35)
- sigma recruits RNA polymerase 3 (this is the holoenzyme sigma+RNA polymerase 3)
- sigma opens the DNA helix
- RNA polymerase 3 begins to add RNA bases
- Sigma releases
- mRNA synthesis continues until the RNA polymerase 3 reaches the transcription termination region of DNA
What does sigma do in prokaryotic RNA transcription
it binds to the promoter region of DNA
10 and 35 base units upstream of the start codon
is sigma used in eukaryotic RNA transcription
no
What makes up the holoenzyme in prokaryotic RNA transcription
Sigma and RNA polymerase 3
What opens the DNA double helix in prokaryotic RNA transcription
sigma
what happens to sigma after RNA polymerase 3 begins adding bases and synthesizing mRNA
it leaves
What are the three main RNA polymerases in eukaryotic, and what is their function
RNA polymerase 1 - rRNA
RNA polymerase 2- mRNA
RNA polymerase 3 - tRNA
is prokaryotic RNA processed
no
is eukaryotic RNA processed
highly
what is involved in eukaryotic rRNA processing
preribosomal rRNAs are cleaved by ribonucleases into the three ribosomal RNAs
What is involved in eukaryotic tRNA processing
- 5’ end is cleaved off
- certain bases are modified
- a portion of the anticodon loop is removed
What is involved in eukaryotic mRNA processing
- 5’ capping
- 3’ polyadenylation
- intron splicing
What is 5’ capping
addition of guanosine to the 5’ end
what is the purpose of 5’ capping
- make the mRNA more stable
- assist in the mRNA leaving the nucleus
- assists in mRNA translation to protein
What is 3’ polyadenylation
the addition of many AAA’s to the 3’ end of mRNA
What is the purpose of 3’ poly AAAA tail
- transcription termination
- helps in translation
- mRNA stability
- assists in mRNA leaving the nucleus
What is intron splicing
the removal of introns (non-coding parts of mRNA)
which are kept in the mRNA, introns or exons
exons
What enzyme does intron splicing
splicosome
what are the two things the splicosome does in removing introns
- exonuclease activity (cuts)
2. ligase activity (binds two mRNA ends together)
What is alternative intron splicing
two or more proteins can be made from one mRNA because some exons can also be removed during intron splicing if the exon is between two introns it can be removed with them
can viral RNA be used to make DNA
yep
What is a codon
a triplet of nucleotides that codes for a specific amino acid
What does it mean that the genetic code is degenerate
one codon can only generate one specific amino acid, but one amino acid can be generated from different codons
What is the start codon
AUG (ATG in the coding strand of DNA)
What are the stop codons
UAA
UAG
UGA
how many potential reading frames are there for RNA
3
how many potential reading frames are there for DNA
6 (3 for each single strand)
What determines which reading frame will be used
the location of the start codon
how many possible codons are there
64 (4 nucleotides in groups of 3)
What are the different types of DNA mutations
- silent mutations
- missense mutations
- nonsense mutations
- splice site mutations
- frameshift mutations
What is a silent mutation
a change in a codon that doesn’t result in a different amino acid
what is a missense mutation
a change in a codon that does result in a different amino acid
what is a nonsense mutation
a change in a codon that results in an early stop codon
what is a splicesite mutation
it alters the way introns are removed
what is a framshift mutation
one or two nucletide addition or deletion that causes the reading frame to shift. from the point of the mutation on, every amino acid will be affected.
what is the wobble effect of tRNA anticodon binding to mRNA codon
the first two bases in the tRNA bind tightly to the first two bases in the mRNA, but the last one doesn’t have to be a perfect match
what does the wobble effect allow
it allows one anticodon (tRNA) to be able to bind to multiple mRNA codons
what are the parts of the ribosome
large and small subunit
what does the ribosome do
brings mRNA and tRNA together and puts the amino acid chain together
What are the 4 steps of protein synthesis
- activation of amino acids
- initiation
- elongation
- termination
what is activation of amino acids
when aminoacyl-tRNA synthetases put an amino acid on the appropriate tRNA
what is the enzyme that adds amino acids to the appropriate tRNA
aminoacyl-tRNA synthetase
how does the initiation step of protein synthesis go
- IF 3 and IF 1 are bound to the small ribosomal subunit
- small subunit binds to the shine delgarno sequence of mRNA
- Fmet-tRNA hooks onto the codon (with help of IF 2)
- all three initiation factors leave
- large subunit binds to the small subunit and mRNA
what is the shine delgarno sequence of mRNA
a purine rich sequence upstream of the start codon to which the small subunit binds
what is the function of IF1 (initiation factor 1)
prevent premature binding of a tRNA to the A site of the ribosome
what is the function of the IF 3 (initiation factor 3)
prevents premature assembly of the small and large subunit
what is the function of IF 2 (initiation factor 2)
helps tRNA fMET get to the p site
What are the three sites of the ribosome
A site
P site
E site
What happens at the A site of ribosomes
new tRNAs enter
What happens at the P site of ribosomes
Peptide bonds are formed between amino acids that are in the A and P sites
what happens at the E site of ribosomes
the used up tRNA’s leave
What are polysomes
when several ribosomes are translating the same mRNA strand
what is coupled transcription/translation
when an mRNA is being transcribed from DNA, and at the same time a ribosome is translating it into a protein
Does coupled transcription/translation happen in eukaryotes
nope, only in prokaryotes
What causes termination of protein synthesis
- stop codon reaches the A site
2. release factors enter
what do release factors do
- cause polypeptide to be released
2. cause the ribosome to dissociate