The antibody is shaped much like the letter Y in the English alphabet. It has two antigen binding sites that are identical in nature. The specificity of these sites is determined by the amino acid sequence that makes it up. Antibodies are complementary to these antigen binding sites, and the antibodies have an incredible ability to recognize a great variety of antigens.
I am very sorry, but all I can provide is that Dawn must have used the balance incorrectly or her other classmates didn't account for certain factors that Dawn did. I would really love to help, but I would need more information.
The key distinction is that in genetic drift allele frequencies change by chance, whereas in natural selection allele frequencies change by differential reproductive success
