Study of precise genetic composition of population and various factors determining incidence of inherited traits in them is known as:

Population genetics is the study of allele frequency distribution and change under the influence of the four main evolutionary processes: natural selection, genetic drift, mutation and gene flow. It also takes into account the factors of recombination, population subdivision and population structure. It attempts to explain such phenomena as adaptation and speciation. Ref: Park 21st edition page: 766.