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Biology Ch. 19
lsue biology 1202
29
Biology
Undergraduate 1
02/10/2012

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Term
Population is a group of organisms of the same species. All individuals living in a particular place at the same time.
Definition
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Term
Allele is an alternative form of a gene
Definition
allele describes the trait
Term
A gene pool of a population includes all the alleles for all the loci present in the population.
Definition
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Term
Locus (plural loci) is the specific location of a gene or DNA sequence on a chromosome.
Definition
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Term
diploid
Definition
(2n) organisms have a maximum of two alleles at each genetic locus
Term
population genetics
Definition
the study of genetic variability in a population and forces that act on it
Term
Evolution of population is best understood in terms of frequencies of proportions of genotype, phenotype, and allele frequencies
Definition
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Term
genotype frequency
Definition
proportion of a genotype in the population
Term
phenotype frequency
Definition
proportion of a phenotype in the population
Term
allele frequency
Definition
proportion of an allele of a given genetic locus in the population
Term
states that allele and genotype frequencies do not change from generation to generation in a large population at genetic equilibrium (no evolution occurring)
Definition
Hardy-Weinberg principle
Term
Assuming random mating, determining the genotype in the next generation by using punnet square
Definition
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Term
In a population:
TT + 2Tt + tt = 100% or
TT + 2Tt + tt = 1
Definition
If T = P, and t = q:
pp + 2pq + qq = 1 or
p(squared) + 2pq + q(squared) = 1
Term
The allele frequencies of a population is described by p + q = 1
p = frequency of dominant allele
q = frequency of the recessive allele
Definition
The genotype frequencies of a population are described by p2 + 2pq + q2 = 1
-p2 is frequency of homozygous dominant genotype
-2pq is frequency of heterozygous genotype
-q2 is frequency of homozygous recessive genotype
Term
What five conditions are required for genetic equilibrium to satisfy Hardy-Weinberg principle?
Definition
1. Random mating
2. No net mutations
3. Large population size
4. No migration between populations
5. No natural selection
Term
How often are the required conditions for the Hardy-Weinberg met?
Definition
rarely
Term
Micro-evolution occurs due to changes in allele frequencies from generation to generation in a population

change in allele or genotype freq. in a population over successive generations

often involves relatively small or minor changes, few generations
Definition
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Term
Micro-evolutionary forces that alter allele freq. in populations?
Definition
nonrandom mating
mutation
genetic drift
gene flow
natural selection
Term
nonrandom mating:
inbreeding and assortative mating
Definition
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Term
Mutations, unpredictable changes in DNA, source of new alleles
Definition
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Term
Genetic drift is a sudden decrease in population size by adverse environmental factors; some die, some couldn't participate in production of next generation
Definition
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Term
Founder effect is a genetic drift that occurs when a small population colonizes a new area: decreases genetic variability
Definition
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Term
gene flow, movement of alleles caused by migration of individuals btw populations
Definition
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Term
natural selection changes genetic composition of population to favor a particular environment
Definition
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Term
Four premises of evolution by natural selection by Charles Darwin
Definition
1. genetic variation
2. reproductive ability of each species
3. organisms compete with one another
4. offspring with most favorable characteristics
Term
modes of natural selection
Definition
stabilizing selection
directional selection
disruptive selection
Term
stabilizing selection favors the mean on phenotype extremes
Definition
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Term
directional selection favors one phenotypic extreme over another causing shift in phenotypic mean
Definition
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Term
disruptive selection favors two of more phenotypic extremes
Definition
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