During the recombination process, extensive processing of the coding e
nds provides tremendous potential diversity to the joint of any two ge
ne segments. However, the diversity of the newborn B and T cell repert
oires is greatly reduced compared with that of the adult. At the mecha
nistic level, this difference is primarily due to the absence of termi
nal deoxynucleotidyltransferase expression until the first week after
birth. Additionally, one direct consequence of the lack of N regions e
arly in ontogeny is the more frequent occurrence of homology-directed
recombination, reducing even further the potential of diversity. Other
enzymatic factors could also contribute to this ontogenic difference.
However, the use of the homology-directed recombination pathway early
in life obscures the analysis of the coding end processing. In this s
tudy we compared the coding end processing throughout ontogeny, in nor
mal and terminal deoxynucleotidyltransferase(-/-) mice in the presence
of minimal homology-directed recombination. The analysis of partial D
-J joints allowed us to avoid potential bias by early selection events
. Our results show that the extent of nucleotide deletion of a given e
nd is consistent throughout ontogeny in the presence or absence of ter
minal deoxynucleotidyltransferase. However, a distinctive processing p
attern is observed for each coding end.