Question

Ribosome binding is determined by ________ in prokaryotes and by _______ in eukaryotes.

Select one:

a. Shine-dalgarno boxes, poly-A tails

b. Shine-dalgarno boxes, methylated caps

c. Poly-A tails, Shine-dalgarno boxes

d. Methylated caps, Shine-dalgarno boxes

e. Pribnow boxes, methylated caps

Answer 1

Ribosome binding is determined by Shine-dalgarno boxes in prokaryotes and by methylated caps in eukaryotes.

so, Correct answer is

b. Shine-dalgarno boxes, methylated caps

The Ribosome binding sites are responsible for correct initiation of translation, these sites are present at 5' (upstream) segment of an mRNA to which ribosome binds and translation started.

In prokaryotes Shine-dalgarno boxes or sequence is a region of prokaryotic mRNA upstream to the start codon. it is a consensus 5'-AGGAGG-3' sequence followed by an initiation codon. it is complementary to the 3' end of the 16S rRNA of smaller subunit of ribosome. In prokaryotes translation and transcription are parallel and when complementary sequence of 16S rRNA  base pairs with Shine-Dalgarno sequence. translation initiation takes place.

In eukaryotes 7-methylguanylate cap (m7G cap) present at  5' end of mRNA due to post transcriptional modifications of mRNA are recognized by eukaryote initiation factors elF4F and poly(A)-binding protein (PABP). After recognition of methylated cap 43S ribosome complex is recruited at 5' end i,e ribosome binding takes place.