MICRO&POP Flashcards
(144 cards)
1
Q
What are the three mechanisms that alter allele frequencies and cause evolutionary change?
A
Natural selection, genetic drift, gene flow
2
Q
Relationship between the Hardy-Weinberg equilibrium condition and mutations?
A
There can be no mutations
Hardy-Weinberg equilibrium is a mathematical model that describes a population where allele frequencies remain constant from generation to generation–pop is not evolving
The gene pool is modified if mutations occur or if entire genes are deleted or duplicated.
3
Q
What does random mating affect in a population?
A
Frequencies of homozygous and heterozygous genotypes
4
Q
Fill in the blank: Natural selection is based on differential success in _______ and _______.
A
survival, reproduction
5
Q
What is the result of natural selection in genetic terms?
A
Alleles being passed to the next generation in differing proportions
6
Q
What is genetic drift?
A
A process where chance events cause allele frequencies to fluctuate unpredictably
7
Q
True or False: Genetic drift has a more significant effect on large populations than small populations.
A
False
8
Q
What is the founder effect?
A
When a few individuals establish a new population with a different gene pool
9
Q
What example illustrates the founder effect in human populations?
A
High frequency of inherited disorders among isolated populations like Tristan da Cunha
10
Q
What does the bottleneck effect refer to?
A
A sudden change in the environment that drastically reduces population size
11
Q
How does genetic drift impact the greater prairie chicken population?
A
Led to low genetic variation and increased frequency of harmful alleles
12
Q
List the five conditions required for Hardy-Weinberg equilibrium.
A
- No mutations
- Random mating
- No natural selection
- Extremely large population size
- No gene flow
13
Q
What can gene flow do to allele frequencies between populations?
A
Alter allele frequencies by moving alleles into or out of populations
14
Q
Fill in the blank: Genetic drift can lead to a loss of genetic _______ within populations.
A
variation
15
Q
What can happen to harmful alleles due to genetic drift?
A
They can become fixed in a population
16
Q
What role does gene flow play in local adaptation?
A
Can affect how well populations are adapted to local environmental conditions
17
Q
True or False: Genetic drift causes allele frequencies to change in a predictable manner.
A
False
18
Q
What happened to the greater prairie chicken population in Illinois from the 1800s to 1993?
A
Dropped from millions to fewer than 50 birds
19
Q
What is gene flow?
A
The transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes.
20
Q
How does gene flow affect allele frequencies?
A
Gene flow can change allele frequencies by introducing new alleles from other populations.
21
Q
What is natural selection?
A
The process that consistently increases the frequencies of alleles that provide reproductive advantage.
22
Q
What are the three types of natural selection?
A
- Directional selection
- Disruptive selection
- Stabilizing selection
23
Q
Define directional selection.
A
A mode of selection where conditions favor individuals exhibiting one extreme of a phenotypic range.
24
Q
Define disruptive selection.
A
A mode of selection that favors individuals at both extremes of a phenotypic range over intermediate phenotypes.
25
Define stabilizing selection.
A mode of selection that acts against both extreme phenotypes and favors intermediate variants.
26
What is relative fitness?
The contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals.
27
What is the significance of the phrase 'survival of the fittest'?
It describes natural selection but can be misleading as it implies direct competition rather than other factors that affect reproductive success.
28
How does sexual selection operate?
* Intrasexual selection
* Intersexual selection
29
What is intrasexual selection?
Selection within the same sex where individuals compete directly for mates of the opposite sex.
30
What is intersexual selection?
Selection where individuals of one sex are choosy in selecting their mates from the other sex.
31
What is sexual dimorphism?
A difference in secondary sexual characteristics between males and females of the same species.
32
What is the role of gene flow in human populations?
It has become increasingly important, leading to an exchange of alleles and fewer genetic differences between populations.
33
True or False: Natural selection is the only mechanism that consistently leads to adaptive evolution.
True
34
What is the effect of environmental changes on adaptive evolution?
Environmental changes can alter what constitutes a 'good match' between an organism and its environment.
35
Fill in the blank: Natural selection acts more directly on the _______ than on the genotype.
phenotype
36
What are some examples of adaptations?
* Ability to change color rapidly in octopuses
* Movable jaw bones in snakes
37
What can prevent natural selection from reducing variation at loci affected by selection?
Balancing selection can maintain genetic variation by preserving some unfavorable alleles.
38
Give an example of directional selection.
An increase in beak depth in Galapagos finches due to an increase in large seeds.
39
What is the impact of genetic drift on allele frequencies?
Genetic drift can cause the frequency of a slightly beneficial allele to either increase or decrease.
40
What is the relationship between natural selection and genetic drift?
Natural selection consistently leads to adaptive evolution, while genetic drift does not.
41
What is balancing selection?
A type of selection that maintains two or more phenotypic forms in a population.
42
What are the two main types of balancing selection?
* Frequency-dependent selection
* Heterozygote advantage
43
Describe frequency-dependent selection.
The fitness of a phenotype depends on how common it is in the population.
44
Give an example of frequency-dependent selection.
The scale-eating fish (Perissodus microlepis) that have left-mouthed and right-mouthed variations.
45
What is heterozygote advantage?
When heterozygous individuals at a locus have greater fitness than both homozygous types.
46
What is an example of heterozygote advantage in humans?
Heterozygotes for the sickle-cell allele are protected against severe malaria.
47
How does natural selection operate on existing variations?
It favors only the fittest phenotypes among the variations present.
48
Why can't evolution result in perfect organisms?
Due to historical constraints, compromises in adaptations, and the interaction of chance, natural selection, and the environment.
49
What is the Hardy-Weinberg equilibrium?
A condition where allele and genotype frequencies remain constant in a population.
50
List the conditions for a population to be in Hardy-Weinberg equilibrium.
* Large population size
* Random mating
* Negligible mutation
* No gene flow
* No natural selection
51
What is genetic variation?
Genetic differences among individuals within a population.
52
How is genetic variation produced in sexually reproducing organisms?
* Crossing over
* Independent assortment of chromosomes
* Fertilization
53
What is genetic drift?
Chance fluctuations in allele frequencies that tend to reduce genetic variation.
54
What is gene flow?
The transfer of alleles between populations, which tends to reduce genetic differences over time.
55
What is directional selection?
A mode of natural selection that favors one extreme phenotype over others.
56
What is disruptive selection?
A mode of natural selection that favors extreme phenotypes at both ends of the spectrum.
57
What is the role of natural selection in adaptive evolution?
It is the only mechanism that consistently causes adaptive evolution.
58
Fill in the blank: The frequency of left- and right-mouthed fish oscillates over time due to _______.
frequency-dependent selection
59
True or False: Natural selection can create new advantageous alleles on demand.
False
60
What can limit adaptation in populations?
Lack of genetic variation and historical constraints.
61
What do heterozygotes exhibit in terms of fitness in case of heterozygote advantage?
Greater fitness than both homozygous types.
62
What does natural selection act upon?
Existing variations in a population.
63
What is the only mechanism that consistently causes adaptive evolution?
Natural selection
## Footnote
Natural selection increases the frequencies of alleles that enhance survival and reproduction.
64
How is relative fitness defined in the context of natural selection?
An organism has greater relative fitness if it leaves more fertile descendants.
65
Name the three modes of natural selection.
* Directional selection
* Disruptive selection
* Balancing selection
66
What does directional selection do to allele frequencies?
It consistently increases the frequencies of alleles that enhance survival and reproduction.
67
What is sexual selection and what can it result in?
Sexual selection can result in secondary sex characteristics that give individuals advantages in mating.
68
What is balancing selection?
Balancing selection occurs when natural selection maintains two or more forms in a population.
69
List some constraints to evolution.
* Natural selection acts only on available variation
* Structures result from modified ancestral anatomy
* Adaptations are often compromises
* Chance, natural selection, and the environment interact
70
True or False: Natural selection can act on any available variation.
False
71
Fill in the blank: The main source of genetic variation among humans is _______.
new mutations
72
What happens if the nucleotide variability of a locus equals 0%?
Gene variability = 0%; number of alleles = 0
73
What is genetic drift?
Genetic drift is the random fluctuation of allele frequencies in a population.
74
What can cause observed genetic variation in isolated populations?
Genetic drift
75
In a population with two alleles, A1 and A2, if 70% of the gametes contain the A1 allele, what is the proportion of flies that carry both alleles?
0.42
76
What is a kettled lake?
A kettle lake formed 14,000 years ago when a glacier melted.
77
Explain the role of mutation in the colonization of a kettled lake.
Mutation may introduce genetic diversity in populations that colonize the lake.
78
How might natural selection affect populations in a newly formed lake?
Natural selection may favor traits that enhance survival in the specific environment of the lake.
79
What is gene flow?
Gene flow is the transfer of alleles or genes from one population to another.
80
What is the effect of genetic drift on small populations?
Genetic drift can lead to significant changes in allele frequencies due to random sampling.
81
True or False: Adaptations are always perfect solutions to environmental challenges.
False
82
What is the significance of secondary sex characteristics?
They can provide mating advantages to individuals.
83
What is genetic variation?
Differences among individuals in the composition of their genes or other DNA sequences
## Footnote
It can result in phenotypic variation, such as color differences in species.
84
What is the Hardy-Weinberg equation used for?
To test whether a population is evolving
## Footnote
It provides a mathematical model for studying genetic variation in populations.
85
What mechanisms can cause the evolution of populations?
Natural selection, genetic drift, and gene flow
## Footnote
These mechanisms alter allele frequencies over time.
86
What is natural selection?
The only mechanism that consistently causes adaptive evolution
## Footnote
It acts on individuals but results in changes in populations over time.
87
What is microevolution?
A change in allele frequencies in a population over generations
## Footnote
It reflects evolutionary changes at a small scale.
88
What is balancing selection?
Maintains two or more phenotypes in a population
## Footnote
It includes frequency-dependent selection and heterozygote advantage.
89
What is directional selection?
A type of selection where one phenotype is favored over others
## Footnote
An example is lighter beetles becoming more common due to predation on darker beetles.
90
How does natural selection affect beak size in finches?
Surviving birds with larger beaks had higher survival rates during drought
## Footnote
This led to an increase in average beak depth in the next generation.
91
What role do mutations play in genetic variation?
They produce new alleles and can lead to changes in phenotype
## Footnote
Mutations can be caused by replication errors or environmental factors.
92
What is heterozygote advantage?
A situation where heterozygous individuals have a fitness advantage
## Footnote
It allows harmful recessive alleles to persist in a population.
93
What is the definition of phenotype?
The product of an inherited genotype and environmental influences
## Footnote
It reflects the observable traits of an organism.
94
What is nucleotide variability?
Variation at the molecular level of DNA sequences
## Footnote
It can occur without causing phenotypic changes.
95
What is the significance of gene duplication in evolution?
It allows for the accumulation of mutations and new gene functions
## Footnote
This process can lead to expanded genomes and new traits.
96
True or False: Individual organisms evolve.
False
## Footnote
Evolution occurs at the population level, not at the individual level.
97
What is a point mutation?
A change in a single nucleotide in a gene's DNA sequence
## Footnote
It can significantly impact phenotype, such as in sickle-cell disease.
98
What is the average percentage of loci that are heterozygous in Drosophila melanogaster?
About 14%
## Footnote
This indicates the level of genetic variation within the species.
99
Fill in the blank: Genetic variation provides the raw material for _______.
evolutionary change
## Footnote
Without genetic variation, evolution cannot occur.
100
What is unequal crossing over?
A process that can lead to gene duplication during meiosis.
101
What can cause chromosomal aberrations?
Unequal crossing over, slippage during DNA replication, or activities of transposable elements.
102
Why are duplications of large chromosome segments often harmful?
They can disrupt essential genes or regulatory regions.
103
What may happen to gene duplications that do not have severe effects?
They can persist over generations, allowing mutations to accumulate.
104
How many functional olfactory receptor genes do humans have?
About 380 functional olfactory receptor genes.
105
How many olfactory receptor genes do mice have?
About 1,200 olfactory receptor genes.
106
What is the average mutation rate in plants and animals?
About one mutation in every 100,000 genes per generation.
107
Why do prokaryotes generate genetic variation quickly?
They have many more generations per unit of time.
108
What is the generation time of HIV?
About two days.
109
Why are single-drug treatments less effective against HIV?
Mutant forms of the virus resistant to a particular drug proliferate quickly.
110
What is the most effective treatment for AIDS?
Drug 'cocktails' that combine several medications.
111
What contributes to genetic variation in sexually reproducing organisms?
Unique combinations of alleles from parents.
112
What are the three mechanisms that contribute to allele shuffling during sexual reproduction?
* Crossing over * Independent assortment of chromosomes * Fertilization.
113
What is the Hardy-Weinberg equation used for?
To test whether a population is evolving.
114
What must occur for evolution to take place in a population?
One or more factors must be at work.
115
What is a gene pool?
All copies of every type of allele at every locus in all members of a population.
116
What does it mean if an allele is fixed in the gene pool?
Only one allele exists for a particular locus in a population.
117
What is the frequency of an allele represented by in population genetics?
p for one allele and q for the other allele.
118
What does Hardy-Weinberg equilibrium indicate?
A population is not evolving at a locus with constant allele and genotype frequencies.
119
How do you calculate the frequency of heterozygotes in a population?
2pq, where p is the frequency of one allele and q is the frequency of the other.
120
What does the sum of all allele frequencies equal in a population?
1 (100%).
121
What happens to genotype frequencies in a population under Hardy-Weinberg equilibrium?
They must add up to 1 (100%).
122
What is the probability that two alleles will come together during reproduction?
p x p for homozygous or p x q for heterozygous.
123
What can occur if a population stops reproducing sexually?
Genetic variation would decrease over time.
124
Fill in the blank: The frequency of the C11 allele is represented by _______.
p.
125
Fill in the blank: The frequency of the cw allele is represented by _______.
q.
126
True or False: Genetic variation is a prerequisite for evolution.
True.
127
What does Hardy-Weinberg equilibrium state about allele frequencies in a population?
If a population is not evolving at a locus with two alleles, the three genotypes will appear in the following proportions: p2, 2pq, q2.
128
What are the expected frequencies of the genotypes CRCR, CRcw, and cwcw when the frequency of the CR allele is 0.6?
Expected frequency of genotype CRCR: 0.36, Expected frequency of genotype CRcw: 0.48, Expected frequency of genotype cwcw: 0.16.
129
What must the sum of the frequencies of the three genotypes equal in a population?
1 (100%)
130
What is the condition for a population to be in Hardy-Weinberg equilibrium?
The observed genotype frequency of one homozygote is p2, the other homozygote is q2, and the heterozygote is 2pq.
131
True or False: A population’s allele and genotype frequencies will change over generations if at least one condition for Hardy-Weinberg equilibrium is not met.
True
132
What is one application of the Hardy-Weinberg equation?
Estimating the percentage of a population carrying the allele for an inherited disease.
133
What is PKU and how is it related to Hardy-Weinberg equilibrium?
PKU is a metabolic disorder resulting from homozygosity for a recessive allele, with a frequency of 1 in 10,000 births.
134
What are the five conditions required for Hardy-Weinberg equilibrium?
* No new mutations
* Random mating
* No natural selection
* Large population size
* No gene flow
135
How is the frequency of the recessive allele for PKU calculated?
q = √(q²)
136
If q² = 0.0001 for PKU, what is the frequency (q) of the recessive allele?
0.01
137
What is the frequency of the dominant allele if the frequency of the recessive allele (q) is 0.01?
0.99
138
Fill in the blank: The Hardy-Weinberg equation is often used as an initial test of whether _______ is occurring in a population.
evolution
139
What is the expected frequency of heterozygotes in the U.S. population if the frequency of the PKU allele is 0.01?
0.0198 (approximately 2% of the U.S. population)
140
How do you calculate the expected genotype frequencies at a locus with two alleles, CG and CY, affecting leaf color?
Use the Hardy-Weinberg equation: p² + 2pq + q² = 1.
141
What is the significance of incomplete dominance in the soybean experiment?
It allows for visual distinction of genotypes based on leaf color.
142
If a population has 85 individuals of genotype AA, 320 of genotype Aa, and 295 of genotype aa, how do you calculate the genotype frequencies?
Divide the number of individuals of each genotype by the total population size.
143
What does it indicate if the observed genotype frequencies do not match the expected frequencies from Hardy-Weinberg equilibrium?
It suggests that evolution may be occurring in the population.
144
What is a hypothesis regarding the frequency changes of alleles in the soybean population over time?
As seedlings age and exhaust food supply, alleles associated with chlorophyll production will change in frequency.
