Mapping the distribution of the telomeric sequence (T2AG3) in the Macropodoidae (Marsupialia) by fluorescence in situ hybridization. II. The ancestral 2n=22 macropodid karyotype
In marsupial karyotypes with little heterochromatin, the telomeric sequence (T2AG3)n, is involved in chromosome rearrangements. Here we compare the distribution of the (T2AG3)n sequence in chromosomes recently derived by fusions and other rearrangements (7–0.5 MYBP) with its distribution in chromosomes derived earlier (24–9 MYBP). We have previously shown that the (T2AG3) n sequence is consistently retained during chromosome rearrangements that are recent (7–0.5 MYBP). We suggest that in less recent rearrangements (24–9 MYBP) the pattern observed is initial retention followed by loss or amplification. We also suggest that the presence of interstitial (T2AG3)n sequence is related to the evolutionary status of single chromosomes rather than entire karyotypes.