When building a phylogenetic tree why is it important to sel

Solution

Ans. Phlogeny is the history of descent of a group of taxa such as species from their common ancesters including the order of branching and sometimes the times of divergence. It is important to select a molecular marker in building a phylogenetic tree because molecular markers are favoured over morphological data.The underlying fact useful for molecular systematics is that different genes accumulate mutations at different rates.THe difference depends on how much change a gene can tolerate without losing its function.For example, histone molecules may become non-functional if some amino acids are replace with different ones. On the other hand internal transcribed spacers (ITS) of ribosomal RNA can still fold properly if many of its nucleotides are changed. Thus ITS can more rapidly accumulate mutations than histones, reflecting the different functional constraints on their gene product.The advantage of using molecular marker is obvious-molecular data are more numerous than fossil records and easier to obtain.

There is no sampling bias involved, which helps to correct the gaps in real fossil records.A more clear and robust phylogenetic tree can be constructed with the help of molecular markers only.