Exam 3: Evolutionary Genetics

Question 1

biological species concept

Answer 1

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

Question 2

past evolutionary forces can have negative consequences today: phenylthiocarbamide tasting

Answer 2

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

Question 3

biological evolution

Answer 3

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

Question 4

types of evolution: (2)

Answer 4

(evolution as a two-step process)

1. anagenesis
2. cladogenesis

Question 5

anagenesis

Answer 5

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

Question 6

cladogenesis

Answer 6

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)

Question 7

what must be present for evolution to take place

Answer 7

genetic variation

Question 8

what are the 3 types of genetic variation?

Answer 8

1. molecular variation
2. protein variation
3. DNA sequence variation

Question 9

molecular variation

Answer 9

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)

Question 10

protein variation

Answer 10

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

Question 11

measures of genetic variation (2)

Answer 11

1. proportion of polymorphic loci

2. expected heterozygosity

Question 12

explanation for protein variation?

Answer 12

neutral-mutation hypothesis

Question 13

neutral-mutation hypothesis

Answer 13

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)

Question 14

balance hypothesis

Answer 14

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)

Question 15

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

Answer 15

true

Question 16

reproductive isolating mechanisms: (2)

Answer 16

1. prezygotic reproductive isolating mechanisms

2. postzygotic reproductive isolating mechanisms

Question 17

prezygotic reproductive isolating mechanisms (5)

Answer 17

1. ecological
2. behavioral
3. temporal
4. mechanical
5. gametic

Question 18

postzygotic reproductive isolating mechanisms (3)

Answer 18

1. hybrid inviability
2. hybrid sterility
3. hybrid breakdown

Question 19

speciation

Answer 19

process by which new species arise

Question 20

allopatric speciation

Answer 20

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

Question 21

sympatric speciation

Answer 21

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)

Question 22

speciation through polyploidy

Answer 22

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

Question 23

characteristic of behavioral reproductive isolating mechanisms

Answer 23

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

Question 24

characteristic of hybrid inviability

Answer 24

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

Question 25

characteristic of hybrid sterility

Answer 25

acts after a zygote has formed; hybrid is sterile

Question 26

characteristic of hybrid breakdown

Answer 26

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

Question 27

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

Answer 27

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

Question 28

phylogeny

Answer 28

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

Question 29

what is a phylogenetic tree

Answer 29

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)

Question 30

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

Answer 30

changes in homologous characteristics

Question 31

the alignment of homologous sequences

Answer 31

phylogenetic trees are often constructed from DNA sequence data

Question 32

the 2 types of construction of phylogenetic trees

Answer 32

1. distance approach | 2. parismony approach

Question 33

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

Answer 33

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

Question 34

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

Answer 34

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

Question 35

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

Answer 35

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

Question 36

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

Answer 36

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

Question 37

humans today represent the one species that

Answer 37

has survived from the diversity of hominin species

Question 38

types of rates of molecular evolution (3)

Answer 38

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

Question 39

how does rates of molecular variation accumulate?

Answer 39

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

Question 40

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

Answer 40

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

Question 41

the molecular clock:

Answer 41

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)

Question 42

the molecular clock is based on the assumption _

Answer 42

of a constant rate of change in protein or DNA sequence

Question 43

evolution through changes in gene regulation: genome evolution

Answer 43

- exon shuffling | - gene duplication (multigene family concept)

Question 44

exon shuffling

Answer 44

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

Question 45

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

Answer 45

- transposon mediated exon shuffling - crossover during meiotic recombination - nonhomologous recombination

Question 46

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

Answer 46

successive gene duplications

Question 47

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

Answer 47

varies extensively across tumor types or with different mutation rates

Question 48

half of driver substitutions occur in

Answer 48

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

Question 49

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)?

Answer 49

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

Question 50

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

Answer 50

allelic frequency changes

Question 51

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

Answer 51

most molecular variants are functionally equivalent