I need to calculate the probability that 2 patients would have the same SNPs in an assay. I have 16 SNPs being screened for, and I have the probability for each of the 2 alleles for each SNP. They are all varying from about 0.35-0.5. How do I calculate the probability 2 random patients would have identical SNP alleles for all 16 SNPs then? Thanks.
As each patient have 3^16 possible genotypes according to 16 SNPs. Considering a difficulty to predict all possible variants when two patients have the same SNP you can chose one of combination for each allele in SNP which would be the same for two patients. Then, you need to calculate a probability 2 random patients would have identical SNP alleles for all 16 SNPs using the following formula.
Firstly, you need to multiply the probabilities of each of 16 alleles for each patient independently (keeping in mind that the allele pairs should be the same for both patients). Secondly, two possibilities obtained from the first step for each of patients are added. Final number must be your answer.