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Genetics > Exam 3: Evolutionary Genetics > Flashcards

Exam 3: Evolutionary Genetics Flashcards

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Biology 101 flashcards
1
Q

biological species concept

A

a group of organisms whose members are capable of interbreeding with one another but are reproductively isolated from the members of other species

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2
Q

past evolutionary forces can have negative consequences today: phenylthiocarbamide tasting

A

then: if you detect it was a selective advantage for avoidance of harmful compounds in the environment that are often bitter tasting
now: health disadvantage as avoidance of bitter tasting food indicates low fruits and veggies and high in fat diets that can be associated w/ incr risk of heart disease and cancer

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3
Q

biological evolution

A

genetic change in a group of organisms (change in gene frequency in a population)

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4
Q

types of evolution: (2)

A

(evolution as a two-step process)

  1. anagenesis
  2. cladogenesis
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5
Q

anagenesis

A

evolution taking place in a single group (a lineage) with the passage of time
evolution w/in a line across time; cannot cross-breed

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6
Q

cladogenesis

A

splitting of one lineage into two; new species arise (physically or by some other way; genetic accumulation over time and cannot interbreed ex humans and chimps)

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7
Q

what must be present for evolution to take place

A

genetic variation

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8
Q

what are the 3 types of genetic variation?

A
  1. molecular variation
  2. protein variation
  3. DNA sequence variation
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9
Q

molecular variation

A

at its base, all about the molecular interactions. different atoms interacting w/ each other in the nucleus and cytoplasm (molecular data are genetic, provide info about the process of evolution)

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10
Q

protein variation

A

analyze proteins in a population to identify genotype (proteins are hard to sequence) analyzing changes; trying to get a gauge of frequencies across thousands of individuals

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11
Q

measures of genetic variation (2)

A
  1. proportion of polymorphic loci

2. expected heterozygosity

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12
Q

explanation for protein variation?

A

neutral-mutation hypothesis

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13
Q

neutral-mutation hypothesis

A

individuals with different molecular variants have equal fitness at realistic population size
(suggest individuals w/ molecular variation can have an equal fitness and pass their genes on in large populations. a lot of genetic variation scattered and there may not be one perfect genotype so the species as a whole will benefit bc variation is good)

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14
Q

balance hypothesis

A

genetic variation in natural populations is maintained by selection that favors variation (if neutral-mutation hypothesis is true, genetic variation is favored across time in large populations bc of the stability variation brings. collection of indivs=greater variation=greater survival)

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15
Q

t/f: new species arise through the evolution of reproductive isolation

A

true

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16
Q

reproductive isolating mechanisms: (2)

A
  1. prezygotic reproductive isolating mechanisms

2. postzygotic reproductive isolating mechanisms

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17
Q

prezygotic reproductive isolating mechanisms (5)

A
  1. ecological
  2. behavioral
  3. temporal
  4. mechanical
  5. gametic
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18
Q

postzygotic reproductive isolating mechanisms (3)

A
  1. hybrid inviability
  2. hybrid sterility
  3. hybrid breakdown
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19
Q

speciation

A

process by which new species arise

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20
Q

allopatric speciation

A

when a geographic barrier splits a population into 2 or more groups and prevents gene flow btwn the isolated groups

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21
Q

sympatric speciation

A

arises in the absence of any geographic barrier to gene flow; reproductive isolation mechanisms evolve within a single interbreeding population (experiencing 2 different selective pressures that splits them in different directions and prevents interbreeding)

22
Q

speciation through polyploidy

A

(common in plants) sudden bubbling of the # of genomes in an individual

23
Q

characteristic of behavioral reproductive isolating mechanisms

A

acts before a zygote has formed; differences in mating behavior prevent mating (time/season, rituals/dance)

24
Q

characteristic of hybrid inviability

A

acts after a zygote has formed; hybrid zygote does not survive to reproduction

25
Q

characteristic of hybrid sterility

A

acts after a zygote has formed; hybrid is sterile

26
Q

characteristic of hybrid breakdown

A

acts after a zygote has formed; F1 hybrids are viable and fertile, but F2 are inviable or sterile

27
Q

Darwin’s finches consist of 14 species that evolved from a single ancestral species that migrated to the Galapagos Islands and underwent

A

repeated allopatric speciation (as the # of islands increase, the # of species of finches increases)

28
Q

phylogeny

A

the evolutionary relationships among a group of organisms are termed a phylogeny (looking at evolutionary history of species and looking at homologous characteristics)

29
Q

what is a phylogenetic tree

A

a graphical representation of the evolutionary relationships among a group of organisms (evolutionary relationships based on genetic similarity btwn groups: more similar=more closely related=the point at which they shared a common ancestor is more recent in time compared to one they are more distantly related to)

30
Q

the evolutionary history of a group of organisms can be reconstructed by studying _

A

changes in homologous characteristics

31
Q

the alignment of homologous sequences

A

phylogenetic trees are often constructed from DNA sequence data

32
Q

the 2 types of construction of phylogenetic trees

A
  1. distance approach

2. parismony approach

33
Q

there are 3 potential phylogenetic trees for humans, chimpanzees, and gorillas. who is more closely related to each other?

A

we are more similar to chimps (cladogenesis), much more recently we shared a common ancestor (closet living biological relative) even though chimps and gorillas seem to be more similar

34
Q

theories on the role of the environment in human evolution: adaptation to change

A

assume that certain adaptations, such as upright walking (climate was getting drier so stood up to gather food/see predators) or tool making, were associated with drier habitat

35
Q

theories on the role of the environment in human evolution: variability selection process

A

a different hypothesis is that the key events in human evolution were shaped not by any single of habitat (e.g. grassland) or environmental trend (e.g. drying) but rather by environmental instability; not limited to a single type of environment

36
Q

t/f: evolution of the genus HOmo and of the adaptation that typify H. sapiens were associated with the smallest oscillations in global climate

A

false-the LARGEST oscillations; environmental unpredictability would select for the adaptively that we have

37
Q

humans today represent the one species that

A

has survived from the diversity of hominin species

38
Q

types of rates of molecular evolution (3)

A
  1. rates of nucleotide substitution
  2. nonsynonymous and synonymous rates of substitution
  3. substitution rates for different parts of a gene
39
Q

how does rates of molecular variation accumulate?

A

rates of molecular variation accumulate at different rates in different parts parts of different genes; parts that are functionally important do not tolerate changes in their aas, other parts like linker regions are more tolerable, across our genome, and across chromosomes

40
Q

t/f: different parts of genes evolve at different rates

A

true; the highest rates of nucleotide substitution are in sequences that have the least effect on protein function

41
Q

the molecular clock:

A

the rate at which a protein evolves is roughly constant over time, therefore the amt of molecular change that a protein has undergone can be used as a clock (how much accumulation is likely to occur if we know some rate of variation that occurs)

42
Q

the molecular clock is based on the assumption _

A

of a constant rate of change in protein or DNA sequence

43
Q

evolution through changes in gene regulation: genome evolution

A
  • exon shuffling

- gene duplication (multigene family concept)

44
Q

exon shuffling

A

functional domains encoded by individual exxons can be shuffled to create mosaic genes of different but related function

45
Q

what are the different mechanisms through which exon shuffling occur: (3)

A
  • transposon mediated exon shuffling
  • crossover during meiotic recombination
  • nonhomologous recombination
46
Q

human globin genes constitute a multigene family that has evolved through _

A

successive gene duplications

47
Q

we still do not have accurate estimates of the number of mutations required to drive a cancer and whether this

A

varies extensively across tumor types or with different mutation rates

48
Q

half of driver substitutions occur in

A

yet-to-be-discovered cancer genes (# of driver mutations increase, but not linearly)

49
Q

what is the expected frequency of heterozygotes in a population with allelic frequency X and Y that is in Hardy-Weinberg and each allele is present at 50% (e.g. 0.5 each)?

A

2XY 2 x 0.5 x 0.5 = 0.5 (50%)

50
Q

what is the most likely effect of outcrossing on the genetic configuration of a population

A

allelic frequency changes

51
Q

which statement is true of the neutral mutation hypothesis

  • all proteins are functionless
  • natural selection plays no role in evolution
  • most molecular variants are functionally equivalent
  • all of the above
A

most molecular variants are functionally equivalent

Genetics (37 decks)

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