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14. What is isochromosome?

Isochromosome is a structurally abnormal chromosome resulting from loss of

one arm of a chromosome with duplication of other arm. Isochromosome

q[46,Xi(Xq)] contributes to approximately 8 % of patients with TS. Presence of

isochromosome q is associated with increased incidence of autoimmune disor-

ders, deafness, and lower incidence of structural abnormalities. The figure

given below illustrates the development of isochromosome (Fig. 8.6).

Ring Chromosome Deleted Genetic Material

Deleted Genetic Material

Fusion

Breaks in

Chromosome

Fig. 8.5 Evolution of the ring chromosome

Isochromosomes

p arm

q arm

two

p arms

two

q arms

Fig. 8.6 The development of isochromosome (Xpi or Xqi)

8 Turner Syndrome