Q2. Which of the following is NOT involved in eukaryotic translation?

(A) Ribosome             (B) Spliceosome         (C) mRNA       (D) tRNA

Eukaryotic translation synthesizes proteins using ribosomes, mRNA, and tRNA as core components. The spliceosome operates in pre-mRNA splicing during transcription processing, not translation.

Option Analysis

Ribosome (A): Eukaryotic 80S ribosomes assemble from 40S and 60S subunits to decode mRNA codons during initiation, elongation, and termination.

Spliceosome (B): This ribonucleoprotein complex removes introns from pre-mRNA in the nucleus via snRNPs (U1, U2, U4, U5, U6), producing mature mRNA for export to cytoplasm.

mRNA (C): Mature mRNA provides the codon template, with its 5′ cap aiding ribosome binding at the Kozak sequence near AUG start codon.

tRNA (D): Aminoacyl-tRNAs deliver amino acids to ribosome sites (A, P, E), matching anticodons to mRNA codons for peptide bond formation.

Eukaryotic translation components drive protein synthesis in cytoplasm, converting mature mRNA genetic code into polypeptides. This central dogma step follows nuclear transcription and splicing, where spliceosome removes introns to yield export-ready mRNA.

Core Components

Translation relies on three RNA types and ribosomal machinery:

• Ribosome: 80S complex scans mRNA 5′ cap, positions initiator Met-tRNAi at AUG, facilitates elongation via A/P/E sites.

• mRNA: Template with codons read 5′-3′; Kozak sequence (ACCAUGG) optimizes start codon recognition.

• tRNA: Carries activated amino acids; anticodon-codon pairing ensures fidelity during peptide chain assembly.

Spliceosome Exclusion

Spliceosome assembles on pre-mRNA introns during co-transcriptional splicing, absent from cytoplasmic translation. Mutations here disrupt mRNA maturation, not direct translation.

Process Stages

This distinction suits CSIR NET Life Sciences prep, emphasizing transcription-translation separation in eukaryotes.