Answer:
Constructing phylogenetic trees using molecular data
A transformative tool for phylogenetic analysis is DNA sequencing. This method allows us to compare the sequences of orthologous (evolutionarily related) genes or proteins instead of relying solely on the physical or behavioral traits of organisms.
The fundamental concept behind such comparisons is akin to our previous discussion: there is a common ancestor for the DNA or protein sequence, and it may have undergone changes throughout evolutionary history. However, a gene or protein isn't limited to a singular characteristic that exists in two forms.
Instead, every nucleotide in a gene or each amino acid in a protein can be considered an individual feature that can mutate into multiple forms (e.g., A, T, C, or G for nucleotides). Thus, a gene consisting of 300 nucleotides could be interpreted as having 300 distinct features present in 4 states. The data gleaned from sequence analyses—and consequently, the detail we can achieve in a phylogenetic tree—is significantly greater than when we analyze physical characteristics.
To interpret sequence data and uncover the most likely phylogenetic tree, biologists often employ computer software and statistical algorithms. Generally, when sequences of a gene or protein are compared among species:
A larger count of variations indicates less related species
A smaller count of variations indicates more closely related species
