Question

explain molecular phylogeny for five marks........accordingly I have increased the points......​

Answer 1

Answer:

1. Molecular phylogeny is the use of structure of molecules to gain information on an organism
2. The most common approach is the comparison of homologous sequences for genes using an sequence alignment techniques to identify similar that include clustal - w and T - coffe
3. Conserved sequence such as mitochondrial DNA are expected to accumulate mutations over time and assuming constant rate of mutations.
4. One more application is used in determinig a child's paternity known as fingerprint
5. The another application is in DNA barcoding

Answer 2

MOLECULAR PHYLOGENY

Phylogenetics is the science of estimating and analyzing evolutionary relationships. Phylogenetic relationships among micro-organisms are especially difficult to discern. Molecular biology often helps in determining genetic relationships between different organisms. Nucleic acids (DNA and RNA) and proteins are 'information molecules' in that they retain a record of an organism's evolutionary history. The approach is to compare nucleic acid or protein sequences from different organisms using computer programs and estimate the evolutionary relationships based on the degree of homology between the sequences. Nucleic acids and proteins are linear molecules made of smaller units called nucleotides and amino acids, respectively. The nucleotide or amino acid differences within a gene reflect the evolutionary distance between two organisms. In other words, closely related organisms will exhibit fewer sequence differences than distantly related organisms. In particular, the sequence of the small-subunit ribosomal RNA (rRNA) is widely used in molecular phylogeny.One advantage of the molecular approach in determining phylogenetic relationships over the more classical approaches, such as those based on morphology or life cycle traits, is that the differences are readily quantifiable. Sequences from different organisms can be compared and the number of differences can be established. These data are often expressed in the form of 'trees' in which the positions and lengths of the 'branches' depict the relatedness between organisms. Shown below is a three-domain tree of life based on small subunit rRNA Sequence

This tree depicts 3 major branches: eubacteria, archaebacteria, and eukaryotes. The organisms on the early branches on the eukaryote branch are all protozoa or other protists (dark green). The relative distance occupied by these organisms, as compared to the so-called higher organisms (light green), is quite notable. These data are consistent with an extremely long evolutionary history and the extreme diversity among the protozoa. However, the above tree is not entirely consistent with other criteria used to determine relationships between protozoa. Furthermore, phylogenetic trees produced from other gene sequences will produce different topologies. Some of these problems are resolved by combining data into consensus trees. For example, the following tree was derived by combining protein data from elongation factor-1α, actin, α-tubulin, and β-tubulin.This tree shows that the various groups of protozoa are quite diverse and distantly related to each other as well as showing relationships between the protozoa and other eukaryotes.

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