what does the tree of life show
- The distances between branches are not artistic distances.
- Total length is proportional to the mutations that differentiate the two organisms.
- A matrix is built in regards to the relationship between organisms, creating clusters.
The trees produced by the program is a hypothesis, it’s the best guess for the relationship between organisms.
what is a mutation
- Mutations cause DNA sequence differences between species
- Happen at a low rate over time
- DNA sequence differences can correlate with evolutionary distance and time
16s rRNA genes
- Molecular chronometer, present in all cells
- Slowly evolving due to highly conserved ribosome function
Secondary structure is critical to function
- Slowly evolving due to highly conserved ribosome function
what makes for a good molecular chronometer
(why is 16s a good molecular chronometer)
- one that has a conserved function
- not easily mutated
for example, we know that organisms have been evolving over millions of years, and all their genes are evolving as well, but a molecular chronometer will remain the same
aside from acting as a molecular chronometer, what does 16s serve as?
- 16s is a machine, a ribozyme.
-16s is important to help the cell translate mRNA into protein sequence - works with tRNAs that carry amino acids in.
what happens to 16s rRNA if there are mutations
- anywhere where you see stems, you cannot have any mutations or it will ruin the integrity of the secondary structure
- mutations in 16s will lead to no ribosome, thus, no protein synthesis.
what is the most important function of 16s in the small subunit
- to find the start of the mRNA
large subunit vs small subunit ribosome (what type of rRNA found in each)
large subunit: contains two rRNAs (5S and 23S rRNA)
small subunit: contains one rRNA (16S) in bacteria (18S in archaea and eucarya)
what is a progenote?
- A progenote is a hypothetical organism in which cellular information would have been encoded on DNA maintained as unliked genes.
- Genes would not have been linked in chromosomes
- Genetic rather than genomic system
Genomes evolved after the domain splits
what is the conclusion made by Woese?
- His proposal did not change the eucaryotic kingdoms, but revised taxonomy so that the kingdom is not the highest taxonomic level
- The eucarya are poorly classified and revoltionary changes in their taxonomy is occuring because they have mostly adopted molecular phylogenetics.
