Exam 4 Quiz 3 Flashcards
making protein involves
all 3 forms of RNA: mRNA, tRNA, rRNA
mRNA
-uses the genetic code as their language
-reads as a series of triplets called codons
-each codon codes for a specific amino acid
how many possible codons
64
how many amino acids
20
genetic code redundancy
more than 1 codon can code for the same amino acid
wobble site
third site within the codon because it is not needed to define the amino acid
start site
AUG
stop codons
UAG
UAA
UGA
why is reading frame important
the movement or shift down of only one codon can change the amino acid that it codes for changing the genetic code
AUG in bacteria contains
formyl methionine
tRNA
-transfer RNA
-73-93 nucleotides long
-single stranded with secondary structures
-modified bases
why does tRNA have increased stability when compared to mRNA
through the single strands with secondary structures and the modified bases
modified bases
pseudouridine, inosine, D=dihydrouridine, dimethyl guanosine
clover leaf structure
structure of tRNA that is beneficial in that it prevents attack by ribonuclease becasue they typically attacked linear
what forms the clover leaf structure
intra-strand base pairing
functional importance of tRNA
-anti-codon area
-3’ acceptor end
anti codon area
bases that recognize mRNA codons
3’ acceptor end
-attaches 3 bases (cytosine, cytosine, adenine) to 3’ end
-termed CCA
what adds CCA onto the 3’ end
CCA adding enzyme
aminoacyl-tRNA synthase
adds amino acid onto the CCA
rRNA
prime component of ribosomes
ribosomes
-where translation occurs
-site of protein synthesis
-60% rRNA
-40% protein
prokaryotic ribosomal subunits
70S total, 50S large, 30S small
eukaryotic ribosomal subunits
80S total, 60S large, 40S small
rRNA off of 50S subunit
5S and 23S rRNA
rRNA off of 30S subunit
16S rRNA
rRNA off of 60S subunit
5S, 5.8S, and 28S rRNA
rRNA off of 40S subunit
18S rRNA
translation initiation
small subunit is separated from large subunit
what keeps the two subunits separated
IF-3 initiation factor that is bound to the 30S subunit
5’ untranslated region upstream of a gene has…
…Shine dalgarno sequence
Shine Dalgarno sequence
base pairs with the 3’ end of the 16S rRNA which puts AUG into prime recognition
when AUG is in prime recognition then
AUG becomes available for recognition by the tRNA carriers: formyl methionine