BIOL 300 - Chapter 21

what are termination codons recognized?

protein release factors RF1, RF2, RF3 - not aminoacyl-tRNAs

what is the function of RF1?

bacterial release factor that recognizes UAA and UAG

what is the function of RF2?

bacterial release factor that recognizes UAA and UGA

what is the function of RF3?

translation termination facotr that relates to EF-G. it releases RF1 and RF2 from the ribosome when they go to terminate polypeptide translation

what is the structure of RF1 and RF2?

resembles aminoacyl-tRNA EF-Tu and EF-G

how does a tRNA associate with an amino acid?

tthey’re charged with amino acids by aminoacyl-tRNA synthetases, which attach amino acids to tRNA in a 2 step reaction using ATP

how does the tRNA synthetase work?

it aminoacylates all the tRNAs in an isoaccepting group, representing a specific amino acid

what are the two steps of tRNA associating with an amino acid?

Amino acids and ATP will form aminoacyl-AMP after synthetase is there, and amino acid & ATP groups are bound to synthetase. Then, tRNA binds, and is charged with amino acid

what is the genetic code?

table of all codons written in mRNA space, and the amino acids they code - mostly universal and was established early in evolution

how do anticodons relate to codons, mRNA, and DNA?

anticodons are complementary to codons, which are directly produced from mRNA, which is complementary to the template strand of DNA.

how many codons are there?

64 - 61 encode amino acids, and 3 are stop codons

what does it mean that the genetic code is redundant/degenerate?

multiple codons encode for the same amino acid

how are codons for the same amino acid similar?

the third position is often irrelevant and encode sthe same amino acid, or any distinctions are between purines and pyrimidines

what are the exceptions for the genetic code being redundant?

methionine (Met - AUG), tryptophan (Trp - UGG), and UGA are unique because of their third position

what are codons that encode the same amino acid called?

synonymous

what is the wobble rule?

the pairing between codon and anticodon at the first two positions is normal, but wobbles can occur at the third position

why does tryptophan not follow the wobble rule?

tryptophan is only encoded by one codon, so if the 3rd position changes, it’s a different amino acid

what is a synonymous mutation?

mutation in mRNA/tRNa that changes the original codon to a codon that still encodes the same amino acid

what is a conservative mutation?

missense mutation that changes a codon to encode an amino acid with similar biochemistry properties - not the same amino acid, but they have similar functions

are synonymous mutations always silent mutation?

no, some synonymous mutations can still significantly affect translation

what does a similar codon, and the same amino acid mean?

synonymous mutation

what does a similar codon, and a similar amino acid mean?

conservative mutation

do synonymous or conservative mutations affect viability or fertility?

no, because they’re polymorphisms

what is a genetic suppressor?

a mutation in a gene that overcomes the mutation in a different gene

what mutations lead to matching interacting surfaces?

protein interactors, protein-RNA interactors, and RNA interactors

what are mutations in the RNA interactors that lead to matching interacting surfaces?

matching base pairing with splicing (snRNA, mRNA) and translation (tRNA and mRNA)

what is suppressor tRNA?

mutated tRNA that recognizes a mutated codon and suppresses the mutation in mRNA

what does nonsense suppressor tRNA suppress?

nonsense mutations, by leading to a premature stop codon

what does a missense suppressor tRNA suppress?

missense mutation, by recognizing mutated codons to insert either the original amino acid, or the other amino acid to restore protein function