Eukaryotic mRNA attaches to ribosome during translation due to:
Ans. (C) 7-methylguanosine cap(Ref: Harpers Illustrated Biochemistry 31st Ed; Page No- 396)Eukaryotic mRNA has 7-methylguanosine cap at 5' end and poly-A tails at 3' end. The 7-methylguanosine caps help the ribosome to recognize the site of attachment to the mRNA.Once the ribosome binds the 5' end, they then scan downstream until they encounter an AUG Codon (Start codon)AAUAAA is present at the 3' end, is the polyadenylation sequence (Poly A tail); they help stabilize the mRNA, facilitate its exit from the nucleus and aid in translation. After the mRNA enters the cytosol, the poly-A tails is gradually shortened.tRNA molecule serve as adaptors for the translation of the information in the sequence of nucleotides of the mRNA into specific amino acids.Extra EdgeDifferences between Eukaryotes and Prokaryotes in the Initiation of Protein Synthesis EukaryotesProkaryotesInitiation factorseIFs (12 or more)IFs (3)Ribosomes80S (40S and 60S subunits)70S (30S and 50S subunits)Binding of mRNA to small ribosomal subunitCap at 5'-end of mRNA binds elFs and 40S ribosomal subunit containing methionyl tRNAiMet. mRNA is scanned for AUG start codon within the Kozak consensus sequenceShine-Dalgarno sequence upstream of initiating AUG binds to complementary sequence in 16S rRNAFirst amino acidMethionineFormyl-methionine
Poly A tail
tRNA
7-methylguanosine cap
Shine dalgrino sequence
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