A possible fragile‐site at Yq12: Case report and possible relevance to de novo structural rearrangements of the Y‐chromosome

Abstract In a routine chromosome study it was noted that cells from a patient had different lengths of Y‐chromosome: 20% of the cells had a Y‐chromosome with about 40% of the normal length of heterochromatin, whereas the majority of cells had an average sizeYq12 region. A break within Yq12 was found in 3–4% of the cells with the long Yq12 chromosome, indicating the presence of a possible new fragile site. The frequency of cells with the 2 different sizes of Y‐chromosomes was unaffected by culture conditions as was the frequency of cells with a break or gap. Possible consequences of a fragile‐site within Yq12 are discussed.