Question

If you had sequences from several different organisms and wanted to find how the organisms were related what would you do?

Answer 1

Ans: The modern classification techniques which can be use to determine the relationships between organisms are DNA hybridisation, by comparing DNA base sequencing, bya mino acid sequences in specific proteins and also by observing how much precipitate is produced in immunological comparison.

1. In DNA sequencing used the sequences of amino acids is observed and the more similar the base sequence the more recent the common ancestor, therefore the more closely related the species are.

2. DNA hybridisation is used to identify how closely related two species are. The greater the percentage hybridisation, the more bases that are complementary and the more recent the ancestor. Percentage of hybridisation is determined by recording the temperature needed to separate the two DNA strands.

The greater the temperature needed to separate the strands of the hybrid DNA, the more hydrogen bonds between the strands, the more complementary base sequences there are and the more recent the common ancestor.

3.Proteins are used to compare that how closely related species are by comparing the amino acid sequence, as related organisms have similar DNA sequences and so similar amino acid sequences in their proteins. And by immunological comparison, comparing how much precipitate is formed when mixing the antibodies and antigens on a protein together from two different species.

Immunological comparison working:

1. Inject a protein from species A into species B (rabbit), and the rabbit will produce antibodies to bind onto the antigen sites on the protein
2. Antibodies are harvested from the rabbit and mixed with different proteins of other species
3. The antibodies will correspond to the antigens in the other proteins, forming a precipitate
4. The more similar a protein is, the more antibodies will bind it the antigen and more precipitate will form, so the more closely related they are.