Page 519 - Veterinary Immunology, 10th Edition

selected V and J genes are first joined to form a complete V-region
VetBooks.ir gene. The joined V-J genes remain separated from the C gene until

messenger RNA (mRNA) is generated. At that time the unwanted J
genes are excised, and the complete V-J-C mRNA is then translated

to form a light chain (Fig. 17.6).

FIG. 17.6 Construction of an immunoglobulin light chain. Selected
V and J genes are first joined as the intervening genes are deleted.
The VJ and C genes remain separated until RNA splicing occurs. At
that time, the intervening RNA segments are deleted, leaving the V,
J, and C genes together in the mRNA. DNA rearrangement occurs
during early B cell development so that each individual B cell is
committed to making a single form of light chain for its antigen
receptor.

When a heavy chain V region is assembled, its construction
requires the splicing together of IGHV, IGHD, and IGHJ genes (Fig.

17.7). This use of three randomly selected genes enormously
increases the amount of variability. For example, if a pool of 100 V,
10 J, and 10 D genes are recombined, then 100 × 10 × 10 = 10,000
different V regions can be constructed. The recombination of these

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