Alpha satellite DNAs on chromosomes 10 and 12 are both members of the dimeric suprachromosomal subfamily, but display little identity at the nucleotide sequence level

We have investigated the organization and complexity of alpha satellite DNA on chromosomes 10 and 12 by restriction endonuclease mapping, in situ hybridization (ISH), and DNA-sequencing methods. Alpha satellite DNA on both chromosomes displays a basic dimeric organization, revealed as a 6- and an 8-mer higher-order repeat (HOR) unit on chromosome 10 and as an 8-mer HOR on chromosome 12. While these HORs show complete chromosome specificity under high-stringency ISH conditions, they recognize an identical set of chromosomes under lower stringencies. At the nucleotide sequence level, both chromosome 10 HORs are 50% identical to the HOR on chromosome 12 and to all other alpha satellite DNA sequences from the in situ cross-hybridizing chromosomes, with the exception of chromosome 6. An 80% identity between chromosome 6- and chromosome 10-derived alphoid sequences was observed. These data suggest that the alphoid DNA on chromosomes 6 and 10 may represent a distinct subclass of the dimeric subfamily. These sequences are proposed to be present, along with the more typical dimeric alpha satellite sequences, on a number of different human chromosomes.