Exam #2 Flashcards
(139 cards)
1
Q
when does crossover happen
A
prophase 1 of meiosis
2
Q
what results from crossover?
A
recombinants AND nonrecombinants
3
Q
recombinants
A
result of crossover, the physical exchange of parts of homologous chromosomes
4
Q
genetic map
A
diagram showing the relative position of genes along a chromosome
5
Q
map unit
A
the distance between genes resulting in 1% recombination
6
Q
when distances are less than 15 map units…
A
the map distances between adjacent genes can be added to get the distance between the genes at the ends
7
Q
when distances are more than 15 map units apart…
A
the observed recombination frequency is somewhat smaller than the sum of the map distances between genes
8
Q
epistasis
A
MULTIPLE genes affect phenotype; pliotropy = 1 gene MULTIPLE phentotypes
9
Q
Harmful mutations are often eliminated in one or a few generations because
A
they decrease the survival and the capacity to reproduce of those affected
10
Q
genotype-by-environment interaction
A
combination of homozygous (genes) and smoking (environment)
11
Q
For X & Y sex chromosomes, reciprocal crosses…
A
are not equivalent
12
Q
sex chromosomes
A
X and Y chromosomes
13
Q
autosomes
A
chromosomes that are NOT sex chromosomes
14
Q
X is ____(size)___ than Y
A
X is LONGER than Y
15
Q
Regions of homology on tips of chromosomes…
A
allow pairing during meiosis (crossover)
16
Q
Segregation of the sex chromosomes predicts…
A
a 1:1 ratio of females to males
17
Q
who discovered x linked genes
A
Morgan; genetics of fruit flies
18
Q
“wild type”
A
most common phenotype
19
Q
Criss cross inheritance:
A
An X chromosome present in a male in one generation must be transmitted to a female in the next generation, and in the generation after that can be transmitted back to a male
20
Q
Linked
A
genes that are close together in the same chromosome & do NOT assort INDEPENDENTLY
21
Q
nonrecombinants
A
alleles are present in the same combination as the parent
22
Q
crossover
A
the physical exchange of parts of homologous chromosomes, prophase 1 of meiosis
23
Q
the frequency of recombination is a measure of…
A
the genetic distance between linked genes
24
Q
if 2 genes are so close together that crossing over never takes place…
A
we would expect only nonrecombinant chromosomes
25
if 2 genes are located very far apart from each other..
1 or more crossovers will occur, and there will be a 1:1:1:1 ratio of nonrecombinant and recombinant gametes
26
maximum frequency of recombination
50%
27
natural selection results in...
allele frequencies changing from generation to generation according to the allele's impact on the survival and reproduction of indiviuals
28
What did Malthus point out in his Essay on the Principle of Population?
natural populations have the potential to increase in size geometrically, meaning that populations get larger at an ever-increasing rate (does not actually happen doe)
29
fitness
a measure of the extent to which the individual's genotype is represented in the next generation (reproduction)
30
paraphyletic
a group that includes a common ancestor and SOME but not all of its descendents
31
polyphyletic
group of organisms that does not include a common ancestor
32
taxa
tips of the branches that are groups of organisms
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sister groups
two groups that are closest relatives bc they share a common ancestor not shared by any other group
34
speciation
the set of processes by which physically, physiologically, or ecologically isolate populations diverge from one another to the point where they can no longer produce fertile offspring
35
taxonomy
to recognize and name groups of individuals as species, and to group close species into more inclusive taxonomic group
36
phylogenetics
aims to discover the pattern of evolutionary relatedness among groups of species by comparing their anatomical or molecular features
37
phylogenetic tree
hypothesis about the evolutionary history of species
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genus (plural: genera)
closely related species grouped together
39
taxonomic classification order
genus > family > order > class > kingdom >domain
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characters
the anatomical, physiological, or molecular features that make up organisms
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character states
several observed conditions
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character states in diff. species can be similar for 1 of two reasons:
the character state was present in the common ancestor of the two groups and retained over time (common ancestry), OR the character state independently evolved in the two groups as an adaptation to similar environments (convergent evolution)
43
analogous
similarities due to independent adaptation by diff species (result of convergent evolution)
44
what is used in constructing phylogenetic trees?
only homologies
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synamorphies
shared derived character
46
cladistics
phylogenetic reconstruction on the basis of synamorphies
47
parsimony
choosing the simpler of two or more hypotheses to account for a given set of observations
48
the extent of similarity (or distance) indicates...
how recently 2 groups shared a common ancestor
49
single gene traits
each one is determined by variation at a single gene and the traits for the most part are not influenced by environment
50
complex traits
(such as human height) influenced by multiple genes as well as by the environment...found in all organisms...important in human health and disease...phenotype determined by measurement
51
environmental risk factor
a characteristic in a person's surroundings that increases the likelihood of developing a particular disease
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inbred lines
true-breeding strains (homozygous)...often used for research
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complex traits are affected by (one/many) genes
many
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phenotypes of many complex traits show ___ distribution
normal
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complex traits
both genetic factors and environmental factors contribute to variation in phenotype among individuals
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norm of reaction
for any genotype graphically depicts how the environment (x axis) affects phenotype (y axis) across a range of environments
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heritability
the proportion of the total variation due to genetic differences among individuals
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when heritability is 100%...
slope of the line is 1; average phenotype of the offspring from any pair of parents will = the average phenotype of the parents themselves
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when heritability is 0%...
the line representing the trait has a slope of 0. the average phenotype of offspring will be = to the average of the population as a whole, despite the phenotypes of parents
60
cultural transmission
some environmental effects in phenotype (ex: rich parents = rich kids)
61
Single nucleotide polymorphism (SNP)
site in the genome where either of two different nucleotide pairs can occur and where each nucleotide pair is common enough in the population to be present in a random sample of 50 diploid individuals ...AKA single base changes in individuals
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positive selection
natural selection that increases the frequency of a favorable allele
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negative selection
natural selection that decreases the frequency of a deleterious allele
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stabilizing selection
maintains status quo and acts against extremes (ex: human birth weight must be between both extremes) ...keeps a trait the same over time (extremes are eaten)
65
directional selection
leads to a change in a trait over time (finches and their bills size for food) (skewed right or left)
66
artificial selection
form of directional selection...analogous to natural selection but the competitive element is removed
67
disruptive selection
operates in favor of extremes and against intermediate forms (apple maggot flies) (middle is eaten)
68
sexual selection
promotes traits that increase an individual's access to reproductive opportunities
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intrasexual selection
male vs male to get the girl
70
intersexual
not fighting, just compete for attention with bright colors and displays. IN THIS CASE, FEMALES CHOOSE
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migration, mutation, genetic drift, and non random mating..
cause allele frequencies to change, but do NOT lead to adaptations
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migration
movement of individuals from one population to another...results in gene flow (decrease pop's average fitness...ex: white ppl going to the equator and getting sunburn and skin cancer)
73
gene flow
the movement of alleles from one pop. to another
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mutation (increases/decreases) genetic variaton
increases; source of new alleles and the raw material on which other forces act...RARE
75
genetic drift
random change in allele frequencies from generation to generation
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bottleneck
originally large pop. falls to just a few individuals (loss of genetic variation)
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founder event
when a few individuals start a new population (small number of peeps arrive on an island and colonize it) (genetic variation is lost)
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genetic drift has a large effect in...
small populations
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why does nonrandom mating alter genotype frequencies without affecting allele frequencies???
it just rearranges alleles already in the gene pool and, unlike migration or mutation, does not add new alelles to the population
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most evolutionarily significant form of non-random mating
inbreeding (increases the freq. of homozygotes and decreases the # of heterozygotes in a pop. without affecting allele frequencies)
81
The modern synthesis
combines mendelian genetics and darwinian evolution...several genes contribute to a trait
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population genetics
the study of patterns of genetic variation
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species
individuals that can exchange genetic material through interbreeding...a group of individuals capable of sharing alleles with one another
84
gene pool
different combos of alleles drawn from the species (human gene pool..skin color, hair type, eye color, etc)
85
populations
interbreeding groups of organisms of the same species living in the same geographical area
86
2 sources of genetic variation
mutation and recombination
87
somatic
body's tissues
88
germ line
occurring in reproductive cells and then passed on to the next generation
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allele frequency of an allele x is...
number of x's present in the pop. divided by total number of alleles
90
fixed
population that exhibits only one allele at a particular gene
91
3 ways to measure genotype and allele frequencies in populations:
observable traits, gel electrophoresis, and DNA sequencing
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@ genetic levels, evolution is simply...
a change in the frequency of an allele or a genotype from one generation to the next
93
5 hardy weinburg equilibrium conditions
1. no natural selection 2. no migration 3. no mutation 4. large sample (no genetic drift) 5. non-random mating
94
allele frequencies...
p + q = 1 (are p and q)
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genotype frequencies
p^2 + 2pq +q^2 (use for hardy weinburg) (each part)
96
species
groups of interbreeding populations that are reproductively isolated from other such groups
97
morphospecies concept
members of the same species usually look alike (shape, size, coloration)
98
probz with BSC
easier in concept than practice, does not apply to asexual (bacteria) or extinct organisms, ring species and hybridization complicate it
99
ring species
species with populations that are reproductively but not genetically isolated (because of gene flow)
100
hybridization
interbreeding (capable of exchanging genes with other species in their genera) ...occurs mainly in plants
101
prezygotic isolating factors:
behavioral, gametic, mechanical, temporal, geographic/ecological
102
behavioral isolation
individuals mate only with other individuals based on courtship rituals, songs, or other behaviors (chimpanzees dont like humans)
103
gametic isolation
incompatibilities between the gametes of 2 diff species (plants)
104
mechanical incompatibility
genetalia (insects and animals)
105
temporal isolation
time; diff. times of year...or active only during day/night
106
geographic or ecological isolation
space. subtle. (bugs on specific plants)
107
postzgotic isolation factors:
genetic incompatibility
108
genetic incompatibility
genetic dissimilarity (diff # of chromosomes)
109
the more closely related/genetically similar a pair of species...
the less extreme the genetic incompatibility between their genomes
110
partially reproductively isolated
2 pops that have genetically diverged but not far enough for full reproductive isolation (speciation)
111
allopatric speciation
speciation that results from GEOGRAPHICAL separation of populations
112
subspecies
allopatric populations that haven't evolved into speciation but have acquired population-specific traits
113
how does allopatric speciation occur
dispersal and vicariance
114
dispersal
some individuals colonize a distant place (like an island) far from the main source population
115
vicariance
geographic barrier arises within a single population, separating it into two or more isolated populations
116
peripatric speciation
specific kind of allopatric speciation where a few peeps from mainland disperse to a new location REMOTE from the original peeps and evolve separately (dispersal)
117
adaptive radiation
unusually rapid evolutionary diversification in which natural selection accelerates the rates of both speciation and adaption
118
co-speciation
occurs in response to speciation in another species (parasites)
119
sympatric populations
not genetically separated...DISRUPTIVE SELECTION
120
instantaneous speciation
caused by hybridization between 2 species in which the offspring are reproductively isolated from both parents (sympatric)
121
double diploid is called a...
tetraploid
122
polyploidy
multiple chromosome sets
123
allopolyploids
polyploids that are produced from hybridization of two diff species
124
autopolyploids
polyploids derived from an unusual reproductive event
125
reinforcement of reproductive isolation (reinforcement)
process by which diverging populations undergo natural selection in favor of traits that enhance prezygotic isolation, thereby preventing the production of less fit hybrid offspring (mating discrimination)
126
A mutation can go to fixation by selection if...
it is advantageous and by genetic drift
127
primates
mammals that share a # of features: nails rather than claws, front facing eyes, and opposable thumbs
128
humans closest relative is___
the chimpanzees
129
human and chimpanzee dna differ by just ___%
1% (King and Wilson)
130
hominins
species that have arisen on the human side of the human/chimpanzee split (ARDI)
131
bipedal
moving w/ 2 feet and walking upright -- LUCY
132
first homonin
homo ergaster
133
neanderthals
EUROPE AND MIDDLE EAST
134
multiregional hypothesis
modern humans derive from h. ergaster that spread around the world 2 mya
135
out-of-africa hypothesis
modern humans arose from h. ergaster in africa before going to africa around 60K y.a
136
Cann's ___
mtDNA
137
Cro-Magnon
first known pop. of homo sapiens in europe
138
explain why mtdna and the whole genome study may differ
1. diff. patterns of transmission between mtDNA and genomic material (mtDNA from mama only) OR 2. ancient DNA stems from a sex-based difference in interbreeding (neanderthals were male)
139
neoteny
long term evolutionary process in which the timing of development is altered so that a sexually mature organism still retains the physical chracteristics of juvenile form
