Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

Comparing amino acid sequences of a specific protein from each species is the most effective method for determining genetic relationships among modern-day lions, tigers, and domestic cats. This approach allows scientists to closely examine the molecular genetic similarities and differences at a fundamental level. Proteins are made up of amino acids, and the specific sequence of these amino acids is determined by the organism's DNA.

By analyzing the amino acid sequences, researchers can identify direct genetic connections and divergence among the species. This method provides precise information about how closely related the species are based on their evolutionary history. It reflects evolutionary changes over time that are not easily observable through physical traits or behaviors, which can be influenced by environmental factors. Molecular analysis offers a clearer picture of genetic lineage and relationships due to the direct link between DNA, mRNA, and protein synthesis.

In contrast, other methods such as observing habitats, analyzing physical characteristics, or studying behavioral patterns may provide general insights into species' adaptations or lifestyles but do not yield specific data on genetic relationships. These approaches can be affected by various factors and may not accurately reflect the underlying genetic links between the species.