Masked mRNA in eggs of sea urchin and Xenopus
There are also several examples of 'masked mRNA' in eggs and oocytes, which may indicate translational control. This 'masked mRNA' is found in abundant quantity and remains untranslated until after fertilization. There are atleast two examples of this masked mRNA' : (i) the mRNA coding for small subunit of ribonucleotide reductase in clam and sea urcin eggs and (ii) the mRNA for fibronectin in Xenopus unfertilized eggs, remain untranslated until about 6-7 hours after fertilization (midblastula stage). The mechanism of this unmasking is not clearly understood.