AP BIOLOGY

Detailed explanation-1: -In general, the more DNA differences in homologous genes (or amino acid differences in the proteins they encode) between two species, the more distantly the species are related.

Detailed explanation-2: -Because the DNA sequence determines a protein’s amino acid sequence, a gene shared by two closely related organisms should have similar, or even identical, amino acid sequences. That’s because closely related species most likely diverged from one another fairly recently in the evolutionary span.

Detailed explanation-3: -Biologists have perfected techniques for determining the sequence of amino acids in proteins. By comparing the amino acid sequences in homologous proteins of similar organisms and of diverse organisms, evolutionary relationships that might otherwise go undetected can be determined.

Detailed explanation-4: -There are 20 different amino acids. A protein consists of one or more chains of amino acids (called polypeptides) whose sequence is encoded in a gene. Some amino acids can be synthesized in the body, but others (essential amino acids) cannot and must be obtained from a person’s diet.