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Genetics > L18-19: Origin & Evolution of Eukaryotes > Flashcards

L18-19: Origin & Evolution of Eukaryotes Flashcards

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Biology 101 flashcards
1
Q

How old is the oldest microbial fossil?

A

From ~3.75 Billion Years Ago

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2
Q

Which domain is older prokaryotes or eukaryotes?

A

Prokaryotes

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3
Q

How old is the first eukaryotic fossil?

A

~1.6 Billion Years Old

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4
Q

What was the oldest eukaryotic fossil?

A

Tappania plana

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5
Q

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

A

Bangiomorpha

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6
Q

What are metazoans and how old are they?

A

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

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7
Q

How old are the Bangiomorpha?

A

~1.3 BYA

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8
Q

What are Hominids?

A

The group consisting of all modern and extinct great apes

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9
Q

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

A

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

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10
Q

What is morphology?

A

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

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11
Q

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

A

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

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11
Q

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

A

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

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12
Q

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

A

Emile Zuckerkandl and Linus Pauling

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12
Q

What was originally used to make an evolutionary tree?

A

Comparison in DNA sequences

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12
Q

What molecule were used to develop the evolutionary tree?

A

Small subunit (SSU) ribosomal (r)RNA

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13
Q

How do we go from molecules to evolutionary trees?

A

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

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14
Q

Why is SSU rRNA used?

A

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

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15
Q

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

A

Pro: 16S
Euk: 18S

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16
Q

What did the first comprehensive phylogenetic tree look like?

A

Consisted of 3 groups: Bacteria, Archaea and Eucarya

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17
Q

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

A

Eocytes and acrhaea

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18
Q

What idea does the first comprehensive phylogenetic tree also propose?

A

That Eucarya and Archaea share a common ancestor (LECA)

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19
Q

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

A

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

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20
Q

What is the importance of rooting the universal tree?

A

-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)

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21
Q

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

A

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

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22
Q

How can the universal tree be rooted?

A

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

23
Q

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

A

Use shared duplication factors (translation elongation factors)

24
Q

What are translation elongation factors?

A

They are GTPases that drive translation

25
Q

Which translation elongation factors correspond in bacteria and eukaryotes?

A

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

26
Q

Where do eukaryotes originate in the eocyte tree?

A

Within the Archaea

27
Q

Where were eocytes originally isolated from?

A

Extreme environments (thermal springs/ hydrothermal vents)

28
Q

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

A

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

29
Q

What is the hypothesis about the LECA?

A

That it was already a complex cell

30
Q

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

A

Asgard Archaea

31
Q

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

A

Mitochondria

32
Q

What group was the mitochondria found to be in?

A

Bacteria - closely related to alpha-proteobacteria

33
Q

How many proteins does the biggest mitochondrial genome encode?

A

67

34
Q

Which mitochondrial protein is used to investigate bacterial origin?

A

Hsp70

35
Q

What does Hsp70 do in mitochondria?

A

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

36
Q

How did the protein Hsp70 become encoded in eukaryotes?

A

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

37
Q

Why is Entamoeba histolytica investigated?

A

To look at LGT from bacteria

38
Q

What gene has Entamoeba inherited from bacteria?

A

Zinc alcohol dehydrogenase

39
Q

How were genes for eukaryotic TXN and TLN machinery inherited?

A

From a common ancestor shared with Asgard Archaea

40
Q

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

A

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

41
Q

How did Neanderthals and Denisovans originate?

A

Through Homo erectus migration

42
Q

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

A

There was no interbreeding

43
Q

How can the 2 different hypothesis be tested?

A

-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

44
Q

What were the first sequences compared in the different hypothesis?

A

Mitochondrial DNA sequences

45
Q

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

A

Restriction fragment length polymorphisms (RFLP)

46
Q

How was RFLP used?

A

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

47
Q

Which hypothesis did RFLP support?

A

The out of Africa hypothesis

48
Q

What is Paleogenetics?

A

The use of bones to extract DNA

49
Q

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

A

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

50
Q

How was PCR used to compare seqences?

A

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

51
Q

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

A

That there is no interbreeding

52
Q

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

A

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

53
Q

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

A

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

54
Q

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

A

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

55
Q

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

A

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

56
Q

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

A

1-4%

57
Q

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

A

4-6%

58
Q

What is significant about the sequences inherited from Neanderthals?

A

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

Genetics (11 decks)

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