Isochromosome Chromosome dividing in an axis perpendicular to usual axis of division Results when one arm of a chromosome is lost and the remaining arm is duplicated, resulting in a chromosome consisting of two sho arms only or of two long arms. Morphologically identical genetic information in both arms. The most common present in live bihs involves the long arm of the X and is designated as i(X)(q10). The Xq isochromosome is associated with monosomy for genes on the sho arm of X and trisomy for genes on the long arm of X. Associated with tumors - 17q. High chance of development of testicular cancer- 12p.