Question

3. The uniparental inheritance of the human Y chromosome (from father to son) and the human mitochondrial chromosome (from mother to daughter) make it possible to trace these DNA molecules over very long periods of time. In fact, it has proven to be possible to place all living humans on a single phylogenetic tree for the Y chromosome (and a similar tree for the mitochondrial chromosome), rooted at the beginning of our species. Why (how) are the branching events on this tree related to the abundance of those haplotypes among ancient DNA samples? How are the branches related to the history of effective population size? To genetic drift?

Answer 1

Relation of branching events in a phylogenetic tree with the haplotypes of ancient DNA sample show that how species evolved from a common ancestor. If the DNA of ancestor have more haplotypes than there are more species and there are more branches on phylogenetic tree as well.

Branches of phylogenetic tree describe the relation among poulations(i.e. which population share a recent common ancestor). Short branches show recent ancestor.Genetic drift change the frequency of alleles in a population but there is a small chance of change in large population due to genetic drift.