It is known that in Angelman syndrome, the chromosome 15 undergoes deletion in the maternal chromosome while in Prader-Willi it's in the paternal.

I understand it can be detected by FISH or other chromosomal staining methods (which would have been used those times), the chromosome number which underwent the deletion.

How could they figure out which chromosome (maternal or paternal) had undergone the change. My question is, which technique allows the chromosome to be marked maternal or paternal? Which technique was originally used?

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    $\begingroup$ Don't have time to make a proper answer so just leaving a comment. As far as I know there is no way to specifically stain either the maternal or paternal chromosome. It was basically genome analysis of Angelman and Prader-Willi patients to find a correlation with both diseases and a deletion on chr15 (same in both). Genome analysis of parents showed that the inherited deletions showed that Prader-Willi patients always got the deletion from their fathers, and Anelman patients from their mothers. Source: ncbi.nlm.nih.gov/pubmed/2564739 $\endgroup$
    – Jory
    Oct 5 '16 at 2:54
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    $\begingroup$ This was further corroborated by the fact that the key player, the gene Ube3a, was an imprinted gene that had parent-of-origin specific (namely maternal) expression. Source: ncbi.nlm.nih.gov/pubmed/8988171 . It would be expected that a gene expressed this way would only cause disease disease when a deletion was inherited from the parent whose chromosome the gene will be expressed from. A parental deletion would be irrelevant to Angelman syndrome because Ube3a is silenced on the paternal chromosome in the relevant tissues regardless. $\endgroup$
    – Jory
    Oct 5 '16 at 3:02
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    $\begingroup$ The kicker would be a mouse model where maternal Ube3a deletions always cause the phenotype in progeny, and paternal Ube3a deletions never do. This probably exists but I'm too lazy to look. Such breeding experiments would confirm causality as all variables except the maternal deletion would be controlled for, although I'm convinced enough by the genomic correlations with specific parents. $\endgroup$
    – Jory
    Oct 5 '16 at 3:07
  • $\begingroup$ If that's enough of an answer please let me know. $\endgroup$
    – Jory
    Oct 5 '16 at 3:43
  • $\begingroup$ Thanks! Just the first comment was enough for my answer. I wqs assuming this to've been pretty old sruff when genome analysis and all hadn't yet arrived. Thanks. $\endgroup$
    – Polisetty
    Oct 5 '16 at 7:33

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