Homo sapiens
The mixed sample 97:3 was mixed with 97% healthy female DNA and 3% Down syndrome DNA. The sample was diluted to around 20 million molecules. This means that each molecule has a unique starting position in the genome, i.e. it is unique with a high probability. The mixed library was then amplified and sequenced until saturation that is each molecules is seen preferably at least two times. It is then possible to bioinformatically remove molecule copies. The idea is that all or most molecules before amplification should be seen after sequencing, and the bias from amplification should be removed.