translation Flashcards
(118 cards)
are amino acids coded by codons or anticodons
codons
what are codons
3-nucleotide codes for amino acids
is the codon on the mRNA or the tRNA
mRNA
is the anticodon on the mRNA or the tRNA
tRNA
function of tRNA?
required to convert from nucleotide to amino acid
where does translation occur in the cell
cytosol
where in the cytosol does translation occur
on ribosomes
which main enzyme was important for researchers to be able to determine the nucleotide code
polynucleotide phosphorylase
describe the actions of polynucleotide phosphorylase
in the presence of NDPs it will create a polynucleotide without a template
describe how UUU was the first codon to be assigned (ie how they figured out UUU=Phe)
they incubated polyU mRNA with E coli extracts and one radioactive amino acid (repeated for all 20 amino acids). Only one would produce a radioactive protein, and this would be the one that codes for UUU
describe how researchers determined the code for codons with two different nucleotides (As and Cs)
used 5 parts ADP and 1 part CDP + polynucleotide phosphorylase. They determined the likelihood of each possible codon based on the amounts that were added. Based upon the protein product, they determined which aa’s were produced in which amounts
the first base of a codon pairs with the ___ base of the anticodon
third
T or F: codon and anticodon are antiparallel
true
some tRNAs have which weird nucleotide
inosinate (I)
which position of the anticodon is inosinate found in
the third position of the anticodon
which nucleotides of the codon can inosinate base pair with
A U and C
T or F: base pairs of codon-anticodon that contain inosinate are stronger than watson-crick pairings
false; they’re weaker
when more than one codon specifies an amino acid, which nucleotide is often the different one
the third nucleotide of the codon
what is the wobble hypothesis
first two bases of the mRNA codon are under strong watson-crick pairings with the anticodon and confer most of the coding specificity. The third base only pairs loosely, allowing the rapid dissociation of the tRNA during synthesis. Reduces the need for accuracy and increases speed. These rules allow for only 32 tRNA molecules to translate all 61 codons
how many tRNA molecules are needed to translate all 61 codons
32
describe how the wobble hypothesis helps maintain genetic integrity
if there is a random mismatch, there is a 1/3 chance it will be in the wobble position, and therefore may still code for the same amino acid (= silent mutation)
what is the most common type of mutation
transition mutation
what is a transition mutation
a purine is replaced with another purine, or a pyrimidine with another pyrimidine
describe why transition mutations aren’t THAT bad
mismatches in codon positions 1 or 2 tend to change the amino acid, but introduce a similar type of amino acid (ie the product is still hydrophobic, so the damage isn’t that bad)
