Translation of mRNA can be repressed. For example, when iron is low, in human blood, a translational repressor protein binds to the mRNA encoding the iron carrier protein ferritin, and prevents translation of the iron carrier. The initial polypeptide can be cut into different functional pieces, with different patterns of cleavage occurring in different tissues. In some cases, different pieces may be spliced together. Protein function can be modified by addition of methyl, phosphoryl, or glycosyl groups.
Signal sequences direct packaging and secretion.
The signal sequences usually end up cleaved off. Gene expression is subject to many levels of control. Outline the mechanisms at all the levels of control, from gene sequence to final product. Explain why control is useful at different levels. Genotype and phenotype of grl.