4.3.5 Classification & Phylogeny Flashcards
What is homology?
Where organisms are grouped based on features they share
Features are homologous if they are shared by organisms which have evolved from a common ancestor
However limitations, wrong classification can occur.
Instead, DNA, RNA and protein sequencing and immunology has allowed scientists to more accurately classify living organisms.
What are the 3 types of sequence data used to investigate evolutionary relationships between living organisms?
- DNA
- mRNA
- Amino Acids
Scientists choose multiple proteins / regions of genome for a more accurate estimate of evolutionary relatedness. Cytochrome C is often used because it is a protein used in respiration by all eukaryotic organisms
The more similar the sequence, the more related the organisms.
2 organisms with very similar sequences would have separated from their common ancestor more recently
Species separated for longer have had more of a chance to mutate and have have changes occur in their DNA, mRNA and amino acid sequences
DNA can be analysed and compared by sequencing the DNA. Immunology uses antibiotics
What is the process of using immunology to classify organisms?
- Albumin extracted from species
- Injected into rabbits
- Rabbits produce antibodies
- Mix albumins and antibodies
- Complexes are precipitated and weighed
The heavier the precipitate, the greater the degree of complementarity is between antibody and albumin. Eg. Antibodies produced against human albumin will produce a larger amount of precipitate when exposed to chimpanzee albumin compared to rat albumin, chimpanzees are a closer relative than rats.
Why use amino acids when you can look at DNA or mRNA?
- Easier to isolate proteins from cells
- Easier to sequence proteins
However DNA code is degenerate, some amino acids are the same in 2 organisms but different DNA, which may lead to inaccurate classification so DNA has largely taken over in classification
