L8: Phylogenetics and Ribosomes Flashcards
What do ribosomes do, how, function of secondary structure
help translate messenger RNA into protein sequence with tRNA. The 16S rRNA pairs with sequences on mRNA at the ribosomal binding site to align then translation happens in the correct reading frame. Once done the ribosome falls apart
Secondary structure used in C and G pairing, bubble formed if the pair is incorrect
What are ribosomes made of
- proteins and 3 rRNAs with
*large subunit (LSU): 2 rRNAs a 5S and 23S
*small subunit (SSU): 1 rRNA 16S rRNA in bacteria and 18S in eucarya
What are the rRNA sizes
23S, 16S and 5S
Who was the last common ancestor, evidence?
LUCA or LCA - U for universal
*thermophile anaerobe
Evidence
*there are thermophiles in all three domains meaning LCA was the root
*whole progenotes thing…, more of a genetic than genomic system in the RNA world => genomes evolved after the split
*16S genes are in all three domains
What is a progenote and relate it to LUCA
*hypothetical organisms where cellular infromation would have been encoded on DNA and maintained as unlinked genes, meaning the genes would also be unlinked in chromosome (as they are today) => explains why domains evolved from LUCA has differing structures
Explain why RNA first
- RNA codes for proteins but also has catalytic properties + self replication
*meaning RNA performed informations and catalystic roles that now happen in DNA
*as life became compartmentalised RNA become more stable =RNA
What happened to progenotes, what are the two competing orders
*as genes became linked it was easier to to pass complete sets to the next generation
*first Archea /Eucaray vs Bacteria diverged
*second Archeas/Eukarya divergene
RNA world => progenote LUCA or RNA world => progenote => genomic LCA??
NO: verall what a key WOESE conclusion, what needed revision
procaryote concept was not taxonomically sound and the procaryote => eukaryoye pipeline was also invalid meaning older classifications were wrong
Woese did not change eucaryotic kingdoms but revised it so kingdoms were not the highest order
the 5 kingdom thing in eukaraya is BS and is being revised
NO: How does Eucarayl taxonomy look today?
- based on molecular phylogenetics analsyses with small subunit RNA requences
*but some taxonomist still do not objectivey support that it should reflect evolution because we should not discard historical groups even if they are polyphyletic (more than 1 ancestor)
NO: How and why is the tree constructued to suggested closer relationship between Bacteria vs Archea and not a Bac/Arc vs Eukarya division
no experimentale vidence for archea and bacteria to be close together
What are graphical ways to represent phylogenetic trees
- monophyletic taxon
- paraphyletic taxon
- polyphyletic taxon
What is a homolog
same evolutionary origin
