Genetic Code and Translation Flashcards
how are RNA and DNA written (named)?
5’ to 3’
how are proteins written (named)?
from the N-terminus to the C-terminus
what RNA are most responsible for translation?
rRNA, tRNA, mRNA
how can 4 bases specify the 20 different amino acids
some amino acids MUST have more than 1 codon - the code is redundant
how are mRNA messages read?
genetic code is non-overlapping, no spaces
how many reading frames does dsDNA have?
3 possible reading frames on top
3 possible reading frames on bottom
= 6 reading frames
insertion or deletion of one or two nucleotides will lead to what?
frameshift mutation
what will insertion or deletion of three nucleotides lead to?
inframe mutation (insertion or deletion)
what happens when there is insertion or deletion of any multiple of 3 (3,6,9,12)?
nucleotides will lead to larger inflame mutations
what are the stop codons?
UGA
UAG
UAA
what is the start codon?
AUG
what is special about tryptophan and methionine?
only has 1 codon to code for it
in most amino acids, there can be more than 1 _____ to specify that amino acid.
codon
why is the genetic code NEARLY universal?
mitochondria has differences, not as many base pairing like in our chromosomal nuclei
what are ribosomes? what are they made of?
they are the RNA machine
made of 2/3 RNA and 1/3 protein
Prokaryotes - odd
Eukaryotes - even
why aren’t the 50S and 30S additive?
they are not perfect spheres, they are different shapes
where on the tRNA is the amino acid attachment site?
3’ OH
where are 3 bases on the mRNA recognized by base pairing?
anticodon loop
what does the anticodon loop 5’ position “wobble” position have?
Inosinate
because of insinuate what can happen?
multiple base pair to different positions on the mRNA
what is the wobble hypothesis?
predicted base pair between the 5’ position of the anticodon and the 3’ position of the codon
if there are 61 codons, how many tRNA do you need?
less than 61 because some tRNAs can read more than 1 codon
what is a charged tRNA?
tRNA carrying amino acid - covalently bonded
how is the reaction of amino acid attachment onto tRNA driven?
by hydrolysis of pyrophosphate
what are the steps in forming a polypeptide polymer from an RNA template?
acitvation of the monomer initiation elongation termination processing the polymer
one mRNA has how many reading frames
3
what does snoRNA do?
splice rRNA
what does snRNA do?
splice mRNA
how many reading frames does ds DNA have?
6
which ribosome is bigger E or P?
eukaryote - more proteins
what can I pair with?
U, C or A
what happens during activation of translation?
to charge tRNA
- enzyme bound amino-acid-adenylate
- formation of amino acyl tRNA
what do eukaryotes use as the first amino acid in translation?
AUG - methionine Met
what do prokaryotes use as the first amino acid in translation?
N-formyl methionine
prokaryotes have 2tRNAs for methionine what do they do?
one allows formation of fMet, the other recognizes internal AUG codons
when is GTP hydrolysized during initiation?
as the 50S subunit joins to form the 70S complex ribosome
where is shine delgarno sequence found? what does it have?
only in prokaryotes - sequence is purine (A,G) rich and resides a few bases 5’ to start the condon
what are the 3 steps in elongation (translation)?
binding of aminoacyl tRNA
formation of peptide bond
translocation of mRNA relative to ribosome
what catalyzed the activity of the portino of the 50S ribosome in elongation?
ribozymes
What is EF-G
prokaryotic - GTPase protein
what is EF-G in eukaryotes called?
EF-2
why does the zymogen activateion of an inactive precursor even happen post translation?
to protect the cell from begin digested by its own products - digestive proteins, capases to activate apotheosis
how many nucleotide bases are in a codon?
3
what are the codons for glycine (gly)/
GG -A GG-U GG- C GG-G *can have any nucleotide base in third position (3')
what structure of tRNA resembles a clover leaf?
secondary
what nucleotide bases are at the 3’ end OH group where the aa attaches?
CCA
what is special about the tRNA alanine with IGC anticodon?
3 codons for alanine so I can bind with U C or A
what permits the base pairing between two purines?
adenosine/ionsine arrangement between codon/anticodon
what is the only free aminoacyl-tRNA to bind to the P site first in prokaryotes?
tRNA fMet
Catalyzed by an enzymatic activity of the RNA portion of the 50S ribosome
–a Ribozyme
prokaryotes: polycistronic or monocistronic?
poly
eukaryotes: polycistronic or monocistronic?
mono
what is interesting about prokaryotic translation?
transcription and translation are coupled
why isn’t eukaryotic translation not coupled?
because of nuclear membrane
how many tRNA do eukaryotic and prokaryotes have?
2 each
why do they need 2 tRNAs
the idea is to get the FIRST Met to the Psite to allow initiation
on what amino acids does protein phosphorylation by a kinase take place?
Ser/Thr
more common than tyrosine phosphorylation
phophate is transfered from ATP to protein
what is an example of a tyrosine kinase?
insulin receptor - phosphate is transfered from ATP to protein tyrosine
what way do glycan groups always face in glycosylation?
always face extracellular side
what is O linked glycolsylation of Ser/Thr?
glycolsylation of the OH gropus
what is N linked glycosylation
glycosylation of asparagine not glutamine!!!
how does the cell target RAS to the plasma membrane?
lipid anchor mechanism
What is preproinsulin?
Translation of the polypeptide is directed into the lumen of the rER and forms “preproinsulin”
how is proinsulin formed?
The signal sequence is cleaved in the lumen of the rER
