Nahr

Fig. 1. Rare recombination events in spermatogenesis generate a low frequency of recombinant haplotypes. Rare sperm in which selected allelic homologous recombination (AHR) or nonallelic homologous recombination (NAHR) events have occurred are shown in gray. Gray/black arrows indicate homologous sequences. Variants that differ between the homologous sequences are shown above the arrow. Novel haplotypes diagnostic of different reciprocal recombination events are show for (A) NAHR: deletion and duplication and (B) AHR. The problem of identifying recombination (AHR or NAHR) events in sperm can, therefore, be reduced to one of identifying recombinant haplotypes in sperm DNA against a high background of nonrecombinant haplotypes.

Fig. 1. Rare recombination events in spermatogenesis generate a low frequency of recombinant haplotypes. Rare sperm in which selected allelic homologous recombination (AHR) or nonallelic homologous recombination (NAHR) events have occurred are shown in gray. Gray/black arrows indicate homologous sequences. Variants that differ between the homologous sequences are shown above the arrow. Novel haplotypes diagnostic of different reciprocal recombination events are show for (A) NAHR: deletion and duplication and (B) AHR. The problem of identifying recombination (AHR or NAHR) events in sperm can, therefore, be reduced to one of identifying recombinant haplotypes in sperm DNA against a high background of nonrecombinant haplotypes.

Table 1 Known NAHR Hotspots

Size of Maximum contiguous size of homology Factor of Disease Chr. Repeats Hotspot hotspot block enhancementa Refs.

Azoospermia

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