Chapter 9-test 2 Flashcards
(17 cards)
Boundaries of translation are defined by
start codon-
stop codon-
- corresponds to the N-terminus of the protein
- corresponds to the C-terminus
5’ untranslated region (5’ UTR) and 3’ UTR
segments outside of the translated regions
phase differences in bacteria and eukaryotes
how the start codon is identified when translation starts
Translational Initiation
- small ribosomal subunit binds near the 5’ end and identifies start codon
- RNA carries first amino acid, binds to start codon
- large subunit joins the small subunit, forms ribosome
Polypeptide Elongation
beings w/ elongation factor (EF) proteins and uses energy of GTP hydrolysis to:
- Recruit tRNAs to the A site
- Form peptide bonds b/w amino acids
- Translocate ribosome in 3’ direction along mRNA
- Recruit tRNAs to the A site
Translation Termination
-one of three stop codons (UAA, UAG, UGA) enters A site
-All organisms use release factors (RF) to bind a stop codon in A site
-The polypeptide bound to tRNA at P site is released
while RF is ejected and ribosomal subunits separate
In bacteria
ribosomes begin translating mRNAs that haven’t been completed
Each polypeptide-producing gene in eukaryotes produces
monocistronic mRNA
operons
Groups of bacterial and archaeal genes. share single promoter
Transfer RNAs
are adaptor molecules that interpret and then act on
information carried in mRNA
isoaccepting tRNAs
tRNA molecules with different anticodons for the same amino acids
how many different codons that specify amino acids?
61
most genomes have
30 to 50 different tRNA genes
third-base wobble
A relaxation of the strict complementary base-pairing rules at third base of codon
Most synonymous codons can be grouped into pairs. the pairs either
both carry a purine (A or G) or both carry a pyrimidine (C or U)
third base wobble occurs through
flexible pairing at the 3’-most nucleotide of codon and the 5’-most nucleotide of anticodon
Eukaryotic mRNAs translation happens where?
cytoplasm.
