L18-19: Origin & Evolution of Eukaryotes

Question 1

How old is the oldest microbial fossil?

Answer 1

From ~3.75 Billion Years Ago

Question 2

Which domain is older prokaryotes or eukaryotes?

Answer 2

Prokaryotes

Question 3

How old is the first eukaryotic fossil?

Answer 3

~1.6 Billion Years Old

Question 4

What was the oldest eukaryotic fossil?

Answer 4

Tappania plana

Question 5

What is the first eukaryotic fossil that looks like a modern eukaryote?

Answer 5

Bangiomorpha

Question 6

What are metazoans and how old are they?

Answer 6

they are the group that contains all modern animals and they were founded around 635MYA

Question 7

How old are the Bangiomorpha?

Answer 7

~1.3 BYA

Question 8

What are Hominids?

Answer 8

The group consisting of all modern and extinct great apes

Question 9

What were Darwin’s beliefs regarding the origin and tree of life?

Answer 9

-Life was descended from a common ancestor (LUCA)
-The descent from the common ancestor is tree like (phylogeny tree)

Question 10

What is morphology?

Answer 10

The study of forming a 3D structure used to find relationships between animals (e.g. Homo erectus)

Question 11

What was studied in the paper: Molecules as Documents of Evolutionary History?

Answer 11

The sequences of DNA, RNA and proteins from different species could be used to infer their evolutionary relationships (the start of molecular evolutionary biology)

Question 11

What is the disadvantage of using morphology to reconstruct evolutionary relationships?

Answer 11

Cannot be used for bacteria as it cannot be used to tell the microorganisms apart

Question 12

Who wrote the paper: Molecules as Documents of Evolutionary History?

Answer 12

Emile Zuckerkandl and Linus Pauling

Question 12

What was originally used to make an evolutionary tree?

Answer 12

Comparison in DNA sequences

Question 12

What molecule were used to develop the evolutionary tree?

Answer 12

Small subunit (SSU) ribosomal (r)RNA

Question 13

How do we go from molecules to evolutionary trees?

Answer 13

-Make an alignment or gene or protein seq
-Measure similarity
-Convert similarity to evolutionary distance (uses mathematical model)
-Draw a tree that best fits

Question 14

Why is SSU rRNA used?

Answer 14

it is essential in all of life as it evolves in a complicated way (different rates)

Question 15

What is the difference between SSU rRNA in prokaryotes and eukaryotes?

Answer 15

Pro: 16S
Euk: 18S

Question 16

What did the first comprehensive phylogenetic tree look like?

Answer 16

Consisted of 3 groups: Bacteria, Archaea and Eucarya

Question 17

What are Crenarcheota known as and what domain do they belong to?

Answer 17

Eocytes and acrhaea

Question 18

What idea does the first comprehensive phylogenetic tree also propose?

Answer 18

That Eucarya and Archaea share a common ancestor (LECA)

Question 19

Why are the genes rarely replaced by lateral gene transfer (LGT) in the tree of life?

Answer 19

As there is negative selection against replacement of genes for the strong core of genomes

Question 20

What is the importance of rooting the universal tree?

Answer 20

-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)

Question 21

Why can’t the tree of life be properly rooted?

Answer 21

Because the mapping of the nucleus is different in different ancestors, all that is known is that prokaryotes existed before eukaryotes

Question 22

How can the universal tree be rooted?

Answer 22

Using an outgroup (species not a member of the group to be rooted)

Question 23

What is a different way to find an outgroup to find the root?

Answer 23

Use shared duplication factors (translation elongation factors)

Question 24

What are translation elongation factors?

Answer 24

They are GTPases that drive translation

Question 25

Which translation elongation factors correspond in bacteria and eukaryotes?

Answer 25

EF-Tu and EF-G (bacteria) correspond to EF-1 and EF-2 (eukaryotes)

Question 26

Where do eukaryotes originate in the eocyte tree?

Answer 26

Within the Archaea

Question 27

Where were eocytes originally isolated from?

Answer 27

Extreme environments (thermal springs/ hydrothermal vents)

Question 28

What is the new best supported hypothesis for the position of eukaryotes in the tree of life?

Answer 28

There are actually 2 domains of life and eukaryotes are actually located within the archaea

Question 29

What is the hypothesis about the LECA?

Answer 29

That it was already a complex cell

Question 30

Which new group of archaea has been found to have similar processes to eukarya?

Answer 30

Asgard Archaea

Question 31

What is a main component of cells that is used to find the origin of the eukaryote?

Answer 31

Mitochondria

Question 32

What group was the mitochondria found to be in?

Answer 32

Bacteria - closely related to alpha-proteobacteria

Question 33

How many proteins does the biggest mitochondrial genome encode?

Answer 33

67

Question 34

Which mitochondrial protein is used to investigate bacterial origin?

Answer 34

Hsp70

Question 35

What does Hsp70 do in mitochondria?

Answer 35

Important for protein import into the mitochondria and assembly of Fe-S clusters (essential in yeast mitochondria)

Question 36

How did the protein Hsp70 become encoded in eukaryotes?

Answer 36

Endosymbiosis through lateral gene transfer (LGT) and horizontal gene transfer (HGT)

Question 37

Why is Entamoeba histolytica investigated?

Answer 37

To look at LGT from bacteria

Question 38

What gene has Entamoeba inherited from bacteria?

Answer 38

Zinc alcohol dehydrogenase

Question 39

How were genes for eukaryotic TXN and TLN machinery inherited?

Answer 39

From a common ancestor shared with Asgard Archaea

Question 40

What are the 2 main theories for the origin of modern humans?

Answer 40

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

Question 41

How did Neanderthals and Denisovans originate?

Answer 41

Through Homo erectus migration

Question 42

What was the initial out of Africa hypothesis regarding Neanderthals an Denisovans?

Answer 42

There was no interbreeding

Question 43

How can the 2 different hypothesis be tested?

Answer 43

-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

Question 44

What were the first sequences compared in the different hypothesis?

Answer 44

Mitochondrial DNA sequences

Question 45

What machinery was used to map an early phylogenetic tree of mitochondrial DNA?

Answer 45

Restriction fragment length polymorphisms (RFLP)

Question 46

How was RFLP used?

Answer 46

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

Question 47

Which hypothesis did RFLP support?

Answer 47

The out of Africa hypothesis

Question 48

What is Paleogenetics?

Answer 48

The use of bones to extract DNA

Question 49

How was paleogenetics used in finding the similarities and differences between Neanderthals and Humans?

Answer 49

DNA was extracted and they looked at the nuclear genome and mitochondrial genome

Question 50

How was PCR used to compare seqences?

Answer 50

It was shown that when Neanderthal mito DNA and human DNA was compared there were many similarities

Question 51

What does the evidence show when the sequences between Neanderthals and Humans are compared?

Answer 51

That there is no interbreeding

Question 52

How did they find out if the Neanderthal sequences were genuine?

Answer 52

They used different bones from Neanderthals across Europe and sequenced them to show similarities or differences

Question 53

How did scientists test whether modern populations contained Neanderthal DNA in their genomes?

Answer 53

They identified SNPs by comparing random sequences from 2 modern-day humans and asked if the Neanderthals matched the alleles of the individuals

Question 54

What was found in the comparisons between humans and the Neanderthals?

Answer 54

There is more matches when 1 human is African and the other non-African

Question 55

What does the data suggest about the comparison between modern humans and Neanderthals?

Answer 55

That the modern humans that left Africa and colonized the rest of the world met with and interbred with Neanderthals

Question 56

How much of the genomes of people in Eurasia are derived from Neanderthals?

Answer 56

1-4%

Question 57

How much of the genetic material of Melanesians are derived from Denisovans?

Answer 57

4-6%

Question 58

What is significant about the sequences inherited from Neanderthals?

Answer 58

It can contribute towards the susceptibility of getting a virus and how severe the symptoms of the virus are