Autosomal Ring Chromosomes

Abstract

Abstract Ring chromosomes are uncommon. The typical physical phenotype comprises major dysmorphogenesis and intellectual deficiency, and reproduction is not usually a relevant issue. A ring chromosome is formed due to an end-to-end fusion of chromosome tips. Almost always, the end result is an imbalance and significant phenotypic abnormality. Rarely, however, this is not the case. In this chapter, genetic risks for ring carriers for whom procreation is a realistic likelihood are considered. This chapter distinguishes between those with a normal 46 chromosome count, one being a ring, and those with a 47 chromosome count, the additional chromosome being a (necessarily small) ..