Question

MCAT Tutorial: Eukaryotic Translation

Answer 1

\({\bf{Introduction:}}\)
- eukaryotic mRNA is monocistronic (1 gene, 1 protein)
- mRNA requires processing (splicing, 5'-cap, 3' poly-A tail)
- translation occurs in cytoplasm whereas transcription occurs in the nucleus, so the processes are separated
- transcription started by untranslated 5' sequences, ex: Kozak sequences

Answer 2

\({\bf{Initiation:}}\)
- 40S subunit + Met_tRNA + eIFs form the initiation complex
- complex moves to 5' end
- initiation complex "scans" the mRNA for a start codon
- large ribosomal subunit binds to the complex

Answer 3

\({\bf{Elongation:}}\)
- eEF-1 helps aminoacyl tRNA bind to A site, catalyzes hydrolysis of GTP to GDP
- eEF-2 acts as translocase
- proceeds mostly like prokaryotic elongation for the most part

\({\bf{Termination:}}\)
- eRF1 recognizes stop codons
- eRF3 is GTPase, releases finished polypeptide

Answer 4

\({\bf{5'~Cap}}\)
- translation is typically cap-dependent and starts at 5' end
- some translation is cap-independent and has an internal ribosome translation site, thought to help translation when environment is not ideal

Answer 5

Source material is Chapter 4.8 of MCAT: Biology Review, 2nd edition by Princeton Review