L18-19: Origin & Evolution of Eukaryotes Flashcards
How old is the oldest microbial fossil?
From ~3.75 Billion Years Ago
Which domain is older prokaryotes or eukaryotes?
Prokaryotes
How old is the first eukaryotic fossil?
~1.6 Billion Years Old
What was the oldest eukaryotic fossil?
Tappania plana
What is the first eukaryotic fossil that looks like a modern eukaryote?
Bangiomorpha
What are metazoans and how old are they?
they are the group that contains all modern animals and they were founded around 635MYA
How old are the Bangiomorpha?
~1.3 BYA
What are Hominids?
The group consisting of all modern and extinct great apes
What were Darwin’s beliefs regarding the origin and tree of life?
-Life was descended from a common ancestor (LUCA)
-The descent from the common ancestor is tree like (phylogeny tree)
What is morphology?
The study of forming a 3D structure used to find relationships between animals (e.g. Homo erectus)
What was studied in the paper: Molecules as Documents of Evolutionary History?
The sequences of DNA, RNA and proteins from different species could be used to infer their evolutionary relationships (the start of molecular evolutionary biology)
What is the disadvantage of using morphology to reconstruct evolutionary relationships?
Cannot be used for bacteria as it cannot be used to tell the microorganisms apart
Who wrote the paper: Molecules as Documents of Evolutionary History?
Emile Zuckerkandl and Linus Pauling
What was originally used to make an evolutionary tree?
Comparison in DNA sequences
What molecule were used to develop the evolutionary tree?
Small subunit (SSU) ribosomal (r)RNA
How do we go from molecules to evolutionary trees?
-Make an alignment or gene or protein seq
-Measure similarity
-Convert similarity to evolutionary distance (uses mathematical model)
-Draw a tree that best fits
Why is SSU rRNA used?
it is essential in all of life as it evolves in a complicated way (different rates)
What is the difference between SSU rRNA in prokaryotes and eukaryotes?
Pro: 16S
Euk: 18S
What did the first comprehensive phylogenetic tree look like?
Consisted of 3 groups: Bacteria, Archaea and Eucarya
What are Crenarcheota known as and what domain do they belong to?
Eocytes and acrhaea
What idea does the first comprehensive phylogenetic tree also propose?
That Eucarya and Archaea share a common ancestor (LECA)
Why are the genes rarely replaced by lateral gene transfer (LGT) in the tree of life?
As there is negative selection against replacement of genes for the strong core of genomes
What is the importance of rooting the universal tree?
-It is essential to investigate the directionality of evolution
-Allows investigation of the characteristic of ancestral organisms
-What features were present in cells or membranes (character states)
Why can’t the tree of life be properly rooted?
Because the mapping of the nucleus is different in different ancestors, all that is known is that prokaryotes existed before eukaryotes
How can the universal tree be rooted?
Using an outgroup (species not a member of the group to be rooted)
What is a different way to find an outgroup to find the root?
Use shared duplication factors (translation elongation factors)
What are translation elongation factors?
They are GTPases that drive translation
Which translation elongation factors correspond in bacteria and eukaryotes?
EF-Tu and EF-G (bacteria) correspond to EF-1 and EF-2 (eukaryotes)
Where do eukaryotes originate in the eocyte tree?
Within the Archaea
Where were eocytes originally isolated from?
Extreme environments (thermal springs/ hydrothermal vents)
What is the new best supported hypothesis for the position of eukaryotes in the tree of life?
There are actually 2 domains of life and eukaryotes are actually located within the archaea
What is the hypothesis about the LECA?
That it was already a complex cell
Which new group of archaea has been found to have similar processes to eukarya?
Asgard Archaea
What is a main component of cells that is used to find the origin of the eukaryote?
Mitochondria
What group was the mitochondria found to be in?
Bacteria - closely related to alpha-proteobacteria
How many proteins does the biggest mitochondrial genome encode?
67
Which mitochondrial protein is used to investigate bacterial origin?
Hsp70
What does Hsp70 do in mitochondria?
Important for protein import into the mitochondria and assembly of Fe-S clusters (essential in yeast mitochondria)
How did the protein Hsp70 become encoded in eukaryotes?
Endosymbiosis through lateral gene transfer (LGT) and horizontal gene transfer (HGT)
Why is Entamoeba histolytica investigated?
To look at LGT from bacteria
What gene has Entamoeba inherited from bacteria?
Zinc alcohol dehydrogenase
How were genes for eukaryotic TXN and TLN machinery inherited?
From a common ancestor shared with Asgard Archaea
What are the 2 main theories for the origin of modern humans?
The multiregional model: modern human populations arose independently in different parts of the world from isolated populations of Homo erectus
Out of Africa hypothesis: modern humans originated in Africa, members of this species moving into the rest of the old world displacing the descendants of Homo erectus that they encountered
How did Neanderthals and Denisovans originate?
Through Homo erectus migration
What was the initial out of Africa hypothesis regarding Neanderthals an Denisovans?
There was no interbreeding
How can the 2 different hypothesis be tested?
-By comparing the sequences of modern humans in different populations
-Once isolated, small communities rapidly accumulate genetic differences by genetic drift
-Differences allow relationships to be mapped
What were the first sequences compared in the different hypothesis?
Mitochondrial DNA sequences
What machinery was used to map an early phylogenetic tree of mitochondrial DNA?
Restriction fragment length polymorphisms (RFLP)
How was RFLP used?
By extracting the DNA then purifying it then using restriction analysis to find the banding pattern which provides the more closely related sequences from different areas
Which hypothesis did RFLP support?
The out of Africa hypothesis
What is Paleogenetics?
The use of bones to extract DNA
How was paleogenetics used in finding the similarities and differences between Neanderthals and Humans?
DNA was extracted and they looked at the nuclear genome and mitochondrial genome
How was PCR used to compare seqences?
It was shown that when Neanderthal mito DNA and human DNA was compared there were many similarities
What does the evidence show when the sequences between Neanderthals and Humans are compared?
That there is no interbreeding
How did they find out if the Neanderthal sequences were genuine?
They used different bones from Neanderthals across Europe and sequenced them to show similarities or differences
How did scientists test whether modern populations contained Neanderthal DNA in their genomes?
They identified SNPs by comparing random sequences from 2 modern-day humans and asked if the Neanderthals matched the alleles of the individuals
What was found in the comparisons between humans and the Neanderthals?
There is more matches when 1 human is African and the other non-African
What does the data suggest about the comparison between modern humans and Neanderthals?
That the modern humans that left Africa and colonized the rest of the world met with and interbred with Neanderthals
How much of the genomes of people in Eurasia are derived from Neanderthals?
1-4%
How much of the genetic material of Melanesians are derived from Denisovans?
4-6%
What is significant about the sequences inherited from Neanderthals?
It can contribute towards the susceptibility of getting a virus and how severe the symptoms of the virus are
