Question

Besides adding more data, why would researchers sequence several genres from the nuclear and mitochondrial genomes, as opposed to using just one gene to generate their phylogenetic hypothesis?

Answer 1

Ans. -

Molecular phylogenetics predates DNA sequencing by several decades. It is derived from the traditional method for classifying organisms according to their similarities and differences, as first practiced in a comprehensive fashion by Linnaeus in the 18th century. Linnaeus was a systematicist not an evolutionist, his objective being to place all known organisms into a logical classification which he believed would reveal the great plan used by the Creator - the systema naturae. The classificatory scheme devised by Linnaeus therefore became reinterpreted as a phylogeny indicating not just the similarities between species but also their evolutionary relationships.

Mitochondrial DNA offers several benefits over nuclear DNA when determining phylogenetic pathways, including: Maternal inheritance mitochondrial DNA is inherited from the mother only, providing a much more direct genetic lineage. Mitochondrial DNA and human evolution . Several unique properties of human mitochondrial DNA , including its high copy number, maternal inheritance, lack of recombination, and high mutation rate, have made it the molecule of choice for studies of human population history and evolution.

The mutation rate in mitochondrial DNA is ten times higher than in nuclear DNA because mitochondrial DNA are subject to damage from reactive oxygen molecules released as a byproduct during OXPHOS. In addition, the mitochondrial DNA also lacks the DNA repair mechanisms found in the nucleus.