Non-random chromosome loss in PHA-stimulated lymphocytes from normal individuals

31773 lymphocyte metaphase cells from 280 karyotypically normal men aged 18-46 were examined for chromosome gain or loss. Chromosome loss was much more common than chromosome gain. Frequency of chromosome loss did not conform to a binomial distribution. There is a striking non-linear, inverse relationship between likelihood of loss and chromosome length. Chromosome gain shows a near binomial distribution between cells and no clear relationship to chromosome length. These facts indicate that the hypodiploid cells mostly arose as technical artefacts during slide preparation but that hyperdiploid cells were mainly due to non-disjunctional gain.