BIO373H5 Lecture Notes - Lecture 11: Eocyte Hypothesis, Kary Mullis, Crenarchaeota
Document Summary
Sequences that gradually change over time randomly but constant, used to determine phylogenetic relationships. The small subunit of ribosome (16s in prokaryotes) is used because it"s conserved and present in all organisms. As bacteria evolves, the sequence of chronometer also slowly changes. So, organisms with few changes are more closely related. Chronometers have to be in all groups that you study to use them. Its function must also be the same in each organism. The molecules need to be similar so you can compare the sequence but also needs differences. Examples of chronometers 16s rrna, hemoglobin, atpase. 16s rrna nucleic acid, it"s in all living things, it has the same function in all organisms (protein), it remains constant and has variable regions. The more similar the 16s rrna sequence is, the more closely related the bacteria is. Molecular chronometers have changes in their sequence due to mutations but at a constant rate.
