Genetic variation is a measure of the genetic differences that exist within a population. The genetic variation of an entire species is often called genetic diversity. Genetic variations are the differences in DNA segments or genes between individuals and each variation of a gene is called an allele.For example, a population with many different alleles at a single chromosome locus has a high amount of genetic variation. Genetic variation is essential for natural selection because natural selection can only increase or decrease frequency of alleles that already exist in the population.
Because there will be no bias if the reasearcher knows which drug is being given and the subject wont know what they are being given so both may assume that the subject is going to feel happier and expect to have an elevated mood and relieve feelings of depression. Hope this helps :)
To solve this, you would need to identify the number of amino acids (20) you are dealing with and the number of positions (8) that are available in your polypeptide. so that would come out to 20 x 20 x 20 x 20 x 20 x 20 x 20 x 20 = 20^8