The Origins and Consequences of Chromosome Pathology

Abstract

To deal intelligently with common questions from “chromosomal families,” counselors need a broad knowledge of how gametes form, how chromosomes behave, and how the early conceptus grows. This chapter describes the ways in which chromosomes are transmitted, and the ways in which these processes can go wrong and lead to clinical abnormality. The distinction is made between “pure” aneuploidies, and abnormalities due to structural rearrangement. In particular, meiotic nondisjunction, with respect to the generation of pure aneuploidy, is discussed in considerable detail. The origins of chromosome mosaicism are reviewed. Mention is made of abnormalities due to epigenetic mechanisms.