PGD-CGH Analysis
Cell transfer and Whole Genome Amplification (WGA) reaction
Biopsied trophectoderm cells are washed, transferred into a PCR reaction tube, and the DNA is extracted. A WGA reaction mix is added and the tubes are placed in a PCR cycler where the whole genome is amplified from the few copies of DNA to millions. A reference mixture of normal male DNAs are amplified at the same time in a separate reaction.
Staining
A green dye is added onto the amplified embryo DNA.
A red dye is added onto the amplified reference DNA.
Hybridization
The sample and reference DNAs are mixed and added onto a microarray containing thousands of probes spread across all chromosomes.
The mix is incubated to allow the sample and reference DNA to ‘stick’ to their matching spots on the array.
Scanning and reading
The microarray is washed, and the scanner reads the amount of colour at each point on the microarray.
Equal red and green = normal two copies of the chromosome.
More green = more sample DNA = trisomy (or three copies of the chromosome).
More red = less sample DNA = monosomy (or only one copy of the chromosome).
Interpreting results
The combination of chromosomes from the original biopsy piece are interpreted by scientists. Both the patient and their doctor are advised of the result.
All suitable embryos are then available for future transfer.
