Life span of mrna molecules in the cytoplasm is a key to determining protein synthesis. Eukaryotic mrna is more long lived than prokaryotic mrna. (cid:373)rna life spa(cid:374) is dete(cid:396)(cid:373)i(cid:374)ed i(cid:374) pa(cid:396)t (cid:271)y se(cid:395)ue(cid:374)(cid:272)es i(cid:374) the 5" a(cid:374)d 3" u(cid:374)t(cid:396)a(cid:374)slated (cid:396)egio(cid:374)s. After translation, various types of protein processing, including cleavage and the addition of chemical groups, are subject to control: ca(cid:374) (cid:862)de(cid:272)o(cid:396)ate(cid:863) the protein so it performs some specific functions. Gets rid of proteins because they have already done their job and are not needed anymore. Regulation of gene expression during differentiation and development. Cytoplasmic determinants are maternal substances [rna, proteins] in the egg that influence early development. If unevenly distributed in the egg cytoplasm, daughter cells will contain different cytoplasmic determinants [leads to different gene expression and differentiation] Myotube differentiated: myo- stands for muscle. There are some formations that are predictable: anterior [head], posterior [tail, dorsal [back], ventral [belly, left, right.