Function of the ER:

most eukaryotic cells is to sequester Ca2+ from the cytosol (High concentration of Ca2+-binding proteins in the ER facilitates Ca2+ storage)

#Id: 468

#Unit 2. Cellular Organization

Introns may more freely accumulate point substitutions and other changes due to no selection pressure.

#Id: 469

#Unit 2. Cellular Organization

Introns evolve or accumulate mutations/changes much more rapidly than exons

#Id: 470

#Unit 2. Cellular Organization

Intron do not face selective pressure to produce a polypeptide with a useful sequence hence highly variable.

#Id: 471

#Unit 2. Cellular Organization

Exon sequences are conserved by the negative selection of individuals in which the sequences have changed

#Id: 472

#Unit 2. Cellular Organization

Most intron mutations are expected to be selectively neutral except branch site, splicing junctions, and sequences influencing splicing

#Id: 473

#Unit 2. Cellular Organization

A mutation that confers a more advantageous phenotype to an organism, relative to Individuals in the same population without the mutation, is positive selection of that organism.