Synthesis of an irmnunoglobulin in membrane bound or secretory form is determined by:
Correct Answer: Differential RNA processing
Description: Differential RNA processing "The membrane and secretory forms of Ig heavy chains of all isotypes are generated by alternative RNA processing."- Lymphocyte development: cell selection events and signals during immune ontogeny By Shiv Pilla p277 "Two forms of Ig are synthesized, membrane-bound (mIg) and secretory Ig (sIg). Membrae-bound and secreted Igs are synthesized from mRNA that have been spliced differently. Membrane Igs, but not secreted Igs, have an additional tail made of hydrophobic amino acids at the C-terminal end of the Fc region that helps to anchor the Ig molecule in the plasma membrane. Completed Ig molecules are either released from the ER membrane (secretory Ig) or remain embedded in the membrane (membrane Ig) before being transpoed in vacuoles (or vesicles), which bud off the Golgi, to the plasma membrane. Secretory Ig are transferred by simple physical entrapment within the secretory vacuoles, wheras membrane Ig are transferred attached to the membrane. Fusion of the secretory vacuoles with the plasma membrane results in the membrane Ig being inseed in the plasma membrane while the soluble content of the vesicles are disgorged to the exterior of the cell."- Manual of biological markers of disease By W. J. Van Venrooij, Main A. M. van Venrooij, R. N. Main pB1.1/13 "The mRNAs for secreted and membrane-bound forms are generated by alternative splicing and differential usage of the polyadenylation sites 5' and 3' of the membrane exons"- Immunoglobulin genes By Tasuku Honjo, Frederick W. Alt 2/e p2.37 RNA splicing is a post transcription RNA processing by which introns, regions of RNA that do not code for protein, are removed from the pre-mRNA and the remaining exons connected to re-form a single continuous molecule. Many pre-mRNAs, including those encoding antibodies, can be spliced in multiple ways to produce different mature mRNAs that encode different protein sequences. This process is known as alternative splicing, and allows production of a large variety of proteins from a limited amount of DNA.
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Biochemistry
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