Lecture 6

Question 1

what does the tree of life show

Answer 1

• 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.

Question 2

what is a mutation

Answer 2

• Mutations cause DNA sequence differences between species
• Happen at a low rate over time
• DNA sequence differences can correlate with evolutionary distance and time

Question 3

16s rRNA genes

Answer 3

• Molecular chronometer, present in all cells
  
  • Slowly evolving due to highly conserved ribosome function
    Secondary structure is critical to function

Question 4

what makes for a good molecular chronometer
(why is 16s a good molecular chronometer)

Answer 4

• 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

Question 5

aside from acting as a molecular chronometer, what does 16s serve as?

Answer 5

• 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.

Question 6

what happens to 16s rRNA if there are mutations

Answer 6

• 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.

Question 7

what is the most important function of 16s in the small subunit

Answer 7

• to find the start of the mRNA

Question 8

large subunit vs small subunit ribosome (what type of rRNA found in each)

Answer 8

large subunit: contains two rRNAs (5S and 23S rRNA)
small subunit: contains one rRNA (16S) in bacteria (18S in archaea and eucarya)

Question 9

what is a progenote?

Answer 9

• 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

Question 10

what is the conclusion made by Woese?

Answer 10

• 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.