Blastomere biopsy: Trisomy 21
The cell pictured here is one cell (blastomere) taken from an eight cell embryo. Fluorescent in situ hybridization was performed for two chromosomes (Two color FISH): Chromosomes number 18 and 21. The abnormality present is an extra copy of chromosome 21 (trisomy 21). This is one of the most common abnormalities seen in embryos. Trisomy 21 is responsible for failure of an embryo to implant in the uterus, it is one of the most common causes of miscarriage and in babies born with this problem have birth defects and mental retardation and is called Down’s Syndrome.