??? ??? ?? ? ? ?? ?? ??? ????? ??? ?? ??? ???? ??? ???? ?????.???? ??? ? ?? ??: ??? ??? ???? ???? ??? ? ????.A chromosomal abnormality consisting in the absence of among the copies of chromosome seven in somatic cells. [from NCI]Retinoblastoma is usually a malignant tumor from the establishing retina that occurs in youngsters, ordinarily prior to