2.4 Molecular phylogenetics

Question 1

Molecular data

What is now sequenced?
Why is DNA sequencing useful?

Answer 1

• Soon after the first sequences of macromolecules were obtained, it was realised that sequence data also contained information about evolutionary history – inherited – in the same way that shared derived
• Initially protein sequences, but now DNA sequence data is the most important source of information for systematics – losing a lot of information
• Data is cheaper (ngs), easier to obtain, non-invasive, objective, and comparable across all living things; in some ways also easier to analyse too – phylogenies built using genomics looking at relationships

Question 2

Molecular Evolution

What can we measure?

Answer 2

Mutations sporadic, UV radiation, various environmental things lead to DNA changing

Not all of it will be passed on, mutations have to occur in the germ cells – gametes, shared derived characteristics

It might be that those mutation don’t survive through many generations, organisms subject to selection, genetic drift

Eventually you will get fixed DNA differences, ultimately fixed through mutations

Question 3

Levels of detail in genetic history

Answer 3

We can then see the population and the various lingeages fixed within a bigger species trees – the species tree forms a bigger part of the hierarchical species

We are looking at hierarchical effects when using DNA often we are looking at just DNA sequences, one of our assumptions would be that the gene tree in sequencing the gene in different species, our assumption gene tree reflects – we have to have a few provisos

Question 4

**Coalescence in maternal lineages **

**What is the mitochondrial eve? **

Answer 4

Any gene has its own tree like history very often in reconstructing evolutionary trees we look at mitochondrial DNA as it is only passed on through the maternal lineage, if we look back into deeper history along the top line at various sequences – different maternal lineages – we will evidentially get back to a common ancestor

Coalescence – whole branch of coalescences theory

Whilst this occurs

One of the whole population of genes that didn’t leave and decedents at the top

Mitochondrial Eve – hypothetical common ancestor of all humans

If you sequence mitochondrial DNA and sequence you will get a coalescence – the mitochondrial Eve for humans but it doesn’t mean that that was the only female around it was part of a big population