Chapter 17 Flashcards
transcription
transcribe DNA into RNA
prompter
signal to start transcribing
- codon of 3 nucleotides
how many types of RNA polymerase do bacteria and eukaryotes have
bacteria= 1
eukaryotes- 3 (I, II, III)
initiation (transcription)
RNA polymerase attaches to promoter
elongation (transcription)
RNA grows longer
- RNA polymerase moves along DNA
as RNA peels away, what happens (transcription)
DNA strand rejoins
termination (transcription)
RNA polymerase reaches sequence of based in DNA template to signal end of gene
what happens after termination in transcription
polymerase detaches from RNA molecule & gene
mRNA
encodes amnio acid sequences
- conveys genetic message from DNA
what does eukaryotic mRNA have
introns- interrupting sequences that separate
exons- coding regions
what does transcription end with
termination
what are introns considered
white noise
terminator
signals end of gene
sigma
protein that must bind promoter first & form holoenzyme
- recognizes & binds to promoter
core enzyme
RNA polymerase because it has active site
how are introns removed
splicing
spliceosome & splicing
cut out extra information that isn’t needed
- allows different mRNAs & proteins to be produced from single gene
in eukaryotes, what does splicing do
remove introns & joins exons
pre-mRNA
primary transcript
- in bacteria mRNA are translated immediately & transcript is an immature primary transcript before transcription is complete
ribosomes
site of protein synthesis
- where translation happens
polyribosome
multiple ribosomes attached to an mRNA
in eukaryotes, how are mature mRNAs transported to cytoplasm
by ribosomes
where does translation occur
on surface of ribosome
what are the two subunits of ribosomes
small- holds mRNA in place
large- where peptide bonds form
what is the structure of ribosomes
contain many proteins, ribosomal RNA (rRNA), and can be separated into 2 subunits
what lines up with ribosomes during translation
three tRNAs
what are the 3 sites in the ribosome
- A site
- P site
- E site
A site
acceptor site for aminoacyl tRNA
P site
peptidyl site where a peptide bond forms
E site
where tRNAs without amino acids exit the ribosome
transfer RNA (tRNA)
function as language interpreter
- convert genetic message of mRNA into language of proteins
how does tRNA perform the interpreter task
pick up appropriate amino acid using an anticodon to recognize the appropriate codons in the mRNA
aminoacyl tnRNA
tRNA linked to its amino acid
what is the structure of tRNA
- relatively short
- can form secondary structure by folding
- CCA sequence at 3’ end is binding site for amino acids
aminoacyl-tRNA synthetases
enzymes that “charge” the tRNA by catalyzing the addition of amino acids to tRNAs
- adds amino acids onto tRNA
for 61 different codons, how many tRNA are there
about 40 tRNAs
wobble hypothesis
- Crick
- tRNA can grab more than 1 ingredient
- anticodon of tRNAs can still bind successfully to a codon whose third position doesn’t follow traditional base pair rules
what do ribosomes provide for mRNA and tRNA
binding sites
- subunits and binding sites come together
anticodon
figures out what amino acid codons are coding for
ribosomal RNA (rRNA)
involved in protein synthesis
- helps align mRNA & tRNA on ribosome & catalyzes the formation of peptide bonds
polypeptide chain
strand of amino acids linked by peptide bonds
ribosome binding site
where the small ribosomal subunit bind to the mRNA
initiation factors
control whether initiation can begin or not
translocation
occurs when ribosome slides one codon toward the 3’ end of mRNA
release factor
- protein
- enters the A site
- does not carry an amino acid
- hydrolyzes the bond linking the P-site tRNA to polypeptide chain
- binds to stop codon in terminating translation
molecular chaperones
speed protein folding
what are the three phases of translation
initiation- gets translation to start
elongation- going through A, P, & E to build out chain
termination- stop codon
how is translation initiated in bacteria
- mRNA binds to small ribosomal unit
- initiator tRNA bearing f-Met binds to start codon
- large ribosomal subunit binds so initiator tRNA is in P site
what are the stages of transcription
initiation
elongation
RNA peels away
termination
transcription in bacteria
sigma protein mist bind prompter first RNA polymerase & sigma form a holoenzyme
what happens in bacteria before transcription is complete
ribosomes being translating an mRNA
