Cytotypes of Kirk’s Dik-Dik (Madoqua kirkii,Bovidae) Show Multiple Tandem Fusions

Abstract

Madoqua kirkii, a miniature African antelope, is noted for extensive chromosomal variation that has been categorized in four distinct cytotypes (A–D). In this investigation, we analyzed the A cytotype (2n = 46, FN = 48) using a suite of molecular cytogenetic approaches that entailed (i) whole chromosome and subchromosomal painting by fluorescence in situ hybridization (FISH), (ii) the study of Madoqua centromeric-specific DNA derived from pooled DNA obtained from the centromeric regions of the acrocentric chromosomes, and (iii) DNA from the telomere:centromere junctions of tandemly fused chromosomes. DNA from these sources was used to probe for the persistence of interstitial satellite DNA and residual centromeric sequences in the tandem and centric fusion junctions by PCR and FISH. The analyses show centromeric sequences at two of the six tandem fusion junctions. These data, and those of hybrid specimens (A × B cytotypes) in conjunction with published information permitted an interpretation of the probable sequence of chromosomal rearrangements among the M. kirkii cytotypes. We discuss the findings in the context of chromosomal evolution in these antelopes, and the implications that these hold for ex-situ breeding programs of the species.