Prophase pairing in a mosaic 18p-;iso 18q human female foetus studied by surface spreading.

The pachytene configurations formed in the ovary of a mosaic 18p-;iso 18q human foetus (22 weeks gestation) are analysed using a surface spreading technique. Three features of interest are the apparent meiotic delay of oocyte development, oocyte degeneration, and the triple pairing which occurs in one cell line when the iso 18q both pairs with itself and with the normal chromosome 18.