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Vast majority of t(21q 21q) Down syndrome occur de novo and familial cases are extremely rare.
In familial translocation Down syndrome, One of the parent show 45 chromosomes.
In general, the carrier parent carrying (21q 21q) translocation is phenotypically normal because
significant amount of genetic material has not been lost in the translocation process. Homologous
Robertsonian translocation can be produced either by abnormal gametogenesis... |