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2B - Genetics & Evolution > week 10 > Flashcards

week 10 Flashcards

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Biology 101 flashcards
1
Q

What is the morphological species concept?

A

define species as groups that look similar

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2
Q

2 reasons why morphological species is misleading?

A
  • diff species evolved to mimic eachother
  • many species are cryptic - they look similar to other species
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3
Q

What is the biological species concept?

A

species are groups of interbreeding natural populations that are reproductively isolated from other such groups

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3
Q

What are some problems regarding biological species concept?

A
  • does not apply to asexual organisms
  • impossible to test in practice
  • impossible to classify extinct taxa
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4
Q

2 Locis A and B, mutation arises and fixes in pop 1 and B in pop2, hybrid between 1 and 2 is incompatible.this is an enable of..

A

BDMIs

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4
Q

What are BDMIs?

A

incompatibilities which might not be viable, post zygotic barriers

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5
Q

What is allopatric speciation?

A

speciation driven by physical isolation

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6
Q

Tu locus = GF of tumour
repressor R locus = prevents tumours. what happens here: backcross hillerrii with F1, mendelian combination

A

and there will be fish with tumour allele with no repressor so cancer arrises

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7
Q

What does prezygotic barriers mean? List some examples

A

a set of events that has to take place before F1 is viable and hybrid is formed
1. finding a mate (timing and recognition)
2. mating (difference in genitals etc)
3. egg and sperm interaction (proteins on surface of egg, cryptic female)

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8
Q

Why and how do prezygotuc barriers evolve?

A
  1. as a byproduct of strong divergent selection
  2. reinforcement
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8
Q

Does pre zygotic barriers contribute more to reproductive isolation that BDMIs? why?

A

Yes because they act earlier

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9
Q

How did pre zygotic barriers evolve as a byproduct of strong selection?

A

addapting to diff ecological niches, these species are isolated from being able to mate with eachtother

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10
Q

How did pre zygotic barriers arise due to reinforcement

A

it is a response to already existing isolation, requires existing BDMIs

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11
Q
  1. _____ isolation evolves more quickly than ___ isolation
  2. ___ pairs have greater prezygotuc isolation than ____ pairs
  3. ____ isolation evolved to prevent individuals wasting reproductive effort on unfit hybrids
A
  1. pre zygotic , post zygotic
  2. sympatric , allopathic
  3. pre zygotic
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12
Q

What kind of mutations/alleles would be seen in homozygote genotype combinations in F2 to crate BDMIs

A

recessive

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13
Q

What kind of interaction between genes causes BDMIs

A

epistatic interactions

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14
Q

Null model?

A

statement that isolation geography 2 groups will be unveitable

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15
Q

What do we expect after 20 generations of divergent selection in allopatry for two Drosophila populations?

A

post zygotic isolation evolves, prezgotic isolation in the form of microhabitat evolves

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16
Q

What does the isolation index show in the two Drosophila populations?

A

The isolation index is higher in the two populations after 20 generations, indicating strong postzygotic isolation in the form of mate preference between them.

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17
Q

Why is mate preference not considered reinforcement in this case?

A

It’s not reinforcement because hybrids are not involved in this process, as reinforcement requires the production of hybrids that are less fit, driving further isolation.

18
Q

How do changes in the gut microbiome of Drosophila affect mating behavior?

A

Changes in the gut microbiome due to different food media lead to differences in scent production, which influences mate choice, as the gut microbiome affects how the flies smell to each other.

19
Q

What observation would be support for reinforcement?

A

sympatric pairs show greater pre zygotic isolation than allopatric pairs

19
Q

What are gene trees?

A

Gene trees represent the ancestry of individual genes, capturing the evolutionary history of a specific gene across different species or populations. These trees can show how a particular gene has evolved over time.

20
Q

Why is the ancestry of recombining genomes a mosaic?

A
  • 1 breakpoint per generation per chromosome
  • recombination events lead to switches in ancestry
  • diff set of ancestors at each position genome
20
Q

What is mitochondrial DNA and how is it shown in gene trees?

A

mitochondria is maternally inherited so a lucky female in population had several daughters who’s mt copy fixed due to chance

21
Q

What is incomplete lineage sorting?

A

Incomplete lineage sorting happens when gene trees do not perfectly align with the species tree, especially in relatively young species (species that diverged recently). This can occur because not all genetic variation in the common ancestor gets fully “sorted” into distinct lineages when the species split.

22
Q

What is paraphyly in gene trees?

A

it means that the gene tree suggests a group of species that should be monophyletic (descended from a single common ancestor) instead has a common ancestor that is not part of the group.

23
Q

What is adaptive introgression and how does it affect gene trees?

A

Adaptive introgression occurs when genetic material from one species enters another species’ gene pool and provides an adaptive advantage. It leads to non-random gene trees, where clades reflect the introgressed genes, as those genes stay together in the same clade, even if they come from different species.

24
Q

What is allopolyploid speciation?

A

hybridisation between 2 species, unreduced gametes so both genomes are retained

25
Q

What is homoploid hybrid speciation?

A

new species w/o genome duplication. DMIs will be selected out in subsequent hybrid generations and eventually only compatible combos of parental alleles remain

26
Q

What is the male equivalent of mt eve?

A

Y-Adam is the most common ancestor (MRCA) of all Y chromosome copies

26
Q

What distribution does TMRCA have

A

wide

27
Q

What are toll-like receptors?

A

receptor proteins expressed on macrophages involved in innate immunity.

28
Q

TLR haplotypes have highly unusual ___ distribution, ___ with adaptive introgression

A

spatial, compatible

29
Q

How does the founder effect relate to human migration and genetic variation?

A

The founder population of humans left Africa around 60,000 years ago, with an estimated population of 1,000 individuals. Due to this small founding population, there may be more genetic variation within African populations compared to other human populations, as non-African populations are derived from a smaller subset of genetic diversity.

30
Q

What are the 3 homo species 40000 years ago?

A

Homo sapiens, homo denisova , homo neanderthalensi
(humans, Denisovans and Neanderthals)

31
Q

Who are Neanderthals

A

found mostly in Europe (Asia?), shared genes with humans (non-sub-saharan africans)

32
Q

How do we know humans and neandertals coexisted>

A

coexist because genome has been sequenced, at least one major introgression even tbetween humans and neanderthals (around 60000 years ago when humans migrated out of africa.

33
Q

Why does some non sub saharan africans have some neanderthal genome?

A

introgression

34
Q

Who are Denisovans?

A

diverged from neandertals 600000 years ago so overlapping range with neandertals

35
Q

What are some physiological similarities and differences between humans and Denisovans vs neanderthals?

A
  • neandertals = similar height but larger brains
  • Denisovans = larger skulls
36
Q

Where did the 3 homo species descend from ?

A

homo erectus

37
Q

Who were homo Erectus?

A

ancestors of homo species, evolved in Africa 2mya, left 1.8mya extinct 200000years ago

38
Q

How can we tell evolution is happening?

A

by comparing allele frequencies of 2 or more populations

39
Q

By comparing allele frequency between Han and Tibetan populations, we found high correlation meaning…

A

little to no divergence

40
Q

What is the hypothesis for genetic adaptation in Tibetan populations?

A

There may have been evolution in the Tibetan population due to living in high altitudes.
SNPs in EPAS1 (a gene involved in red blood cell regulation) are favored in Tibet for higher oxygen affinity of RBCs.
This adaptation occurred in as few as 150 generations to better survive in low-oxygen environments.

41
Q

What is the genetic adaptation related to dairy consumption in European populations?

A

4 out of 12 loci are in genes involved in adapting to agricultural diets in Europe.
The strongest selection signal is an SNP mutation responsible for lactase persistence.
In ancient populations, the lactase gene turns off after weaning, but in populations with high dairy intake, it’s advantageous for the gene to remain active to digest lactose.

41
Q

Where did the EPAS1 allele for altitude adaptation come from?

A

denisovan introgression

2B - Genetics & Evolution (9 decks)

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