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The IGH locus is located on the chromosome 14 [1] at band 14q32.33, at the telomeric extremity of the long arm [2,3], whereas the TRA and TRD loci are located on the chromosome 14 [4-6] at band 14q11.2. The TRD locus is embedded in the TRA locus, between the TRAV and TRAJ genes (for detailed references, see [7]).

Vertical red lines indicate the localization of the TRA and TRD loci at 14q11.2 and that of the IGH locus at 14q32.33.
Blue arrows indicate the orientation 5' → 3' of the loci, and the gene group order in the loci. Note that the TRDV gene localized in 3' of the TRDC gene is in inverted orientation of transcription (shown by a small black arrow). The blue arrows are proportional to the size of the loci, indicated in kilobases (kb). The total number of genes in the loci are shown between parentheses. Nine non-mapped IGHV genes which have a provisional designation are not included in this figure.

The orientation of the loci has been determined by the analysis of translocations, involving the TRA, TRD and IGH loci, in leukemia and lymphoma.

Chromosomal localization human IGH, TRA and TRD

IMGT references:
  1. [1] Croce, C.M. et al., Proc. Natl. Acad. Sci. USA, 76, 3416-3419 (1979).
  2. [2] Kirsch, I.R. et al., Science, 216, 301-303 (1982).
  3. [3] Mc Bride, D.W. et al., Nucleic Acids Res., 10, 8155-8170 (1982).
  4. [4] Collins, M.K.L. et al., EMBO J., 3, 2347-2349 (1984).
  5. [5] Croce, C. et al., Science, 227, 1044-1047 (1984).
  6. [6] Rabbitts, T.H. et al., EMBO J., 4, 1461-1465 (1985).
  7. [7] Lefranc, M.-P., Eur. Cytokine Net., 1, 121-130 (1990).
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