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Genetics and evolution > Lecture 3 > Flashcards

Lecture 3 Flashcards

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Biology 101 flashcards
1
Q

Gene

A

a unit of heritable DNA

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2
Q

Allele

A

a variant of a gene

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3
Q

Locus

A

a location on a chromosome

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4
Q

Gene pool

A

the total aggregate of genes in a population at any one time, all copies of all alleles of all genes at all loci

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5
Q

Variation

A

-for evolution to happen heritable genetic and phenotypic variation must exist
-variation may mean that some population members have alleles that are absent in others
-variation may also mean combinations of different traits that are not present in other members

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6
Q

mutation

A

-changes in the nucleotide sequence of DNA
-a key mechanism in producing variation
-can cause new alleles and genes to arise

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7
Q

production of genetic variation

A

mutation
sexual reproduction

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8
Q

how does sexual reproduction produce variation

A

new combinations of genes produced
recombination- exchange of DNA between chromosomes (e.g crossing over)

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9
Q

mutation definition

A

a change in an organisms nucleotide sequence that can result from copying errors during DNA replication

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10
Q

Heritable mutations

A

mutations that occur in the germline (the cell population that produces gametes)
-consequently random variation occurs in gametes

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11
Q

Point mutations

A

a change in one base in a gene
-may have no functional effect
-but if function is affected, a point mutation can have a large impact on phenotype

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12
Q

mutation rates in animals and plants

A

tend to be relatively low
-sperm contributes to 130/140 mutations while the egg only 10

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13
Q

fitness effects of mutations

A

some are harmful causing organisms to become subject to natural selection (deleterious)
some may be selectively advantageous and also become subject to natural selection (beneficial)
some have no effect

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14
Q

microorganism mutation rate

A

much faster than animals or plants

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15
Q

population

A

a localised group of interbreeding individuals that are:
-all from one species
-are reproductively connected
-have overlapping geographic ranges

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16
Q

microevolution

A

change below species level, the smallest scale of evolution

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17
Q

Macroevolution

A

change that occurs above the species level (typically described within phylogenies)

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18
Q

Genetic drift

A

-the 1st mechanism of microevolution
-a change in the frequency of alleles due to random sampling of organisms
-genetic drift tends to reduce variation through loss of alleles

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19
Q

Bottleneck effect

A

change in allele frequencies when a population drops in size
-e.g natural disaster
-some alleles will be less frequent/ not exist altogether
-new allele frequencies may vary greatly

20
Q

Founder effect

A

-change in allele frequencies when a new population splits off from another
-occurs when a few individuals become isolated from the rest of the population
-allele frequencies in isolated pop are different to rest of pop

21
Q

Impacts of the founder effect

A

conservation- founder effects on population alleles may affect viability of captive bred zoo populations

Disease- founder effects on small populations may increase the frequency of harmful alleles

22
Q

Gene flow

A

gene flow is the movement of alleles among populations
-tends to homogenise the genetic makeup of different populations
-gene flow can increase the fitness of a population
-but gene flow could sometimes decrease the fitness of a population

23
Q

Introgression

A

transfer of an alleles from one species to another species
-introgressed genes can have important disease effects

24
Q

Natural selection

A

the 3rd mechanism of microevolution
-it filters variation between individuals to select phenotypes
-the only one that consistently changed allele frequencies and causes consistent adaptive selection

25
Q

Fitness

A

in general evolutionary fitness is reproductive success

26
Q

Relative fitness

A

is the relative contribution an individual makes to the gene pool of the next generation compared to other individuals

27
Q

Directional selection

A

favours individuals at one end of the phenotypic range

28
Q

Disruptive selection

A

favours individuals at both extremes of the phenotypic range

29
Q

Stabilising selection

A

favours intermediate variants and act against extreme phenotypes

30
Q

An adaption

A

a trait that enhances survival and reproduction in its environment

31
Q

The process of adaption

A

Continuous adaptive selection increases the fit between species and their environment
-species have to be fit to survive and reproduce in their environment

32
Q

Why doesn’t natural selection remove all unfavourable alleles?

A

diploidy
balancing selection

33
Q

Diploidy

A

humans have two copies of most genes meaning harmful recessive alleles that can hide from natural selection

34
Q

Balancing selection

A

maintenance of polymorphism (multiple allele variants) by natural selection by:
-heterozygote advantage- heterozygotes have higher fitness than homozgyotes
-frequency-dependant selection- the fitness of a phenotype depends on how common it is in the population

35
Q

Frequency-dependant selection

A

the fitness of a phenotype depends on how common it is in the population

selection will favour whichever phenotype is less common in a population

36
Q

Sexual selection

A

a type of natural selection in which the heritable traits of some individuals make them more likely to gain mates

hence natural selection for mating success

can result in sexual dimorphism

it can favour exaggerated traits in females where females compete for males

37
Q

Sexual dimorphism

A

large differences between the sexes in secondary sexual characteristics

38
Q

Two types of sexual selection

A

intersexual selection
intrasexual selection

39
Q

Intersexual selection

A

between sexes

individuals of one sex are choosy in selecting mates from the other sex

selection favours traits that benefit this

40
Q

Intrasexual selection

A

Within one sex

competition among individual for mates of the opposite sex

selection favours traits that benefit this

41
Q

Disadvantage of sexually selected traits

A

they may not be well adapted in non-sexual ways

however these traits still evolve because the benefits of reproductive success may outweigh the costs

42
Q

The good genes hypothesis

A

sexually selected traits may advertise overall mate quality in genetics

43
Q

Ring species

A

an evolutionary phenomenon which involves gene flow

they are geographic rings of population in which two end populations are reproductively isolated from each other but connected by indirectly connected by a continuous chain of reproducing populations

44
Q

Chromosomal mutation

A

involves long sections of DNA covering many bases

45
Q

Gene duplication

A

duplicates segments of DNA
key mechanism for generating paralogues

46
Q

Paralogue

A

either of a pair of genes derived from the same ancestral gene

Genetics and evolution (15 decks)

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