Principles of genetic technology — practice question

Genome-wide association studies detect connections between single nucleotide polymorphisms (SNPs) and phenotypic traits such as human diseases. SNPs are positions in DNA that differ within a population because of DNA base substitutions. A genome-wide association study examines how genetic variation affects a disease. A very large number of affected people and a very large number of healthy control individuals supply DNA. Microarray chips are then used to determine each individual's genotype at many SNPs. The Wellcome Trust Case Control Consortium (WTCCC) study was a major genome-wide association study. It used a microarray chip that determined each person's genotype at $500\,000$ different SNPs. The study searched for associations between SNPs and $7$ different diseases. For each disease, $2000$ people with the disease were tested. Their findings were compared with those from $3000$ healthy control individuals.