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BIOL 3350: EXAM 2
Genetic Drift |
Change in allele frequencies of a population resulting from sampling error in drawing gametes from the gene pool to make zygotes and from chance variation in the survival and/or reproductive success of individuals, results in nonadaptive evolution. |
Genetic Variation |
Differences among individuals in a population that are due to differences in genotype.
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Environmental Variation |
Differences among individuals in a population that are due to differences in the environments they have experienced. |
Genotype-by-Environment Interaction |
Differences in the effect of the environment on the phenotype displayed by different genotypes. Ex: people living in the same area that have different skin colors in seasons than others. |
Genome |
An organism's complete set of genetic information. |
Alleles |
Variant forms of a gene, or variant nucleotide sequences at a particular locus. |
Genotype |
The combination of alleles an individual carries at one or more loci of interest. |
Phenotype |
The set of traits an individual exhibits. |
Epigenetic Marks |
Chemical modifications of DNA, managed by enzymes encoded in the genome, that can influence phenotype by altering gene expression. |
Phenotype Plasticity |
Variation, under environmental influence, in the phenotype associated with a genotype.
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Mutations |
Modifications to DNA that occur by chance. |
Gene Duplication |
When a piece of a chromosome is duplicated due to unequal crossing over and replication errors. Can involve just one or multiple genes.
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Crossing Over |
The exchange of genetic material between homologous chromosomes that results in recombinant chromosomes during sexual reproduction. |
Paralogous |
Duplicated genes found in the same genome; describes the relationship among members of the same gene family. Type of genetic homology. |
Orthologous |
Genes that diverged after a speciation event; describes the relationship among homologous genes found in different species. |
Polymorphism |
The existence within a population of more than one variant for a phenotypic trait, or of more than one allele. |
Heterozygosity |
That fraction of the individuals in a population that are heterozygotes. |
Cline |
A systematic change along a geographic transect in the frequency of a genotype or phenotype.
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Microsatellite |
Many tandemly repeated nucleotides or genes. |
Minisatellite |
Any of numerous DNA segments located mainly near the ends of chromosomes that consist of repeating sequences of at least five but usually not more than 100 nucleotides and that are useful in DNA fingerprinting. |
PCR |
A laboratory technique used to make multiple copies of a segment of DNA. Compare microsatellite fragment sizes resulting from the amplification. |
DNA Fingerprinting |
The analysis of DNA from samples of body tissues or fluids in order to identify individuals. |
Reaction Norm |
The pattern of phenotypes an individual may develop upon exposure to different environments.
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Point Mutation |
The substitution of one base for another. |
Silent (synonomous) Substitution |
A mutation that leaves the encoded protein unaltered. |
Replacement (nonsynonomous) Mutation |
A mutation that changes the amino specified by a codon. |
Nonsense Mutation |
A mutation that introduces a premature stop codon. |
(Genetic) Linkage |
The tendency for alleles at different loci on a chromosome to be inherited together. |
Population |
For sexual species: a group of interbreeding individuals and their offspring. For asexual species: a group of individuals living in the same area. |
Metapopulation |
A group of populations that are separated by space but consist of the same species.
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Gene Pool |
The set of all copies of all alleles in a population that could potentially be contributed by the members of one generation to the members of the next generation. |
Heterozygote |
An individual having two different alleles of a particular gene or genes, and so giving rise to varying offspring. |
Homozygote |
An individual having two identical alleles of a particular gene or genes and so breeding true for the corresponding characteristic. |
Heterozygote Advantage (Overdominance) |
Desribes a situation in which heterozygotes at a particular locus tend to have higher fitness than homozygotes. |
Underdominance |
Describes a situation in which homozygotes tend to have higher fitness than heterozygotes.
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Frequency-Dependent Selection |
Occurs when an individual's fitness depends on the frequency of its phenotype in the population; typically occurs when a phenotype has higher fitness when it is rare and lower fitness when it is common. |
Mutation-Selection Balance |
Describes an equilibrium in the frequency of an allele that occurs because new copies of the allele are created by mutation at exactly the same rate that old copies of the allele are eliminated by natural selection. |
Fixation |
The elimination from a population of all the alleles at a locus but one. The one remaining allele is now at a frequency of 1. |
Migration / Gene Flow |
The movement of alleles from one population to another, typically via the movement of individuals or via the transport of gametes by wind, water, or pollinators. |
Sampling Error |
A chance difference between the frequency of a trait in a subset of individuals from a population versus the frequency of the trait in the entire population. Larger for smaller samples. |
Founder Effect |
A change in allele frequencies that occurs after a founder event, due to genetic drift in the form of sampling error in drawing founders from the source population. |
Positive Selection |
Selection in favor of advantageous mutations. |
Negative (purifying) Selection |
Selection against deleterious mutations. |
Population Bottleneck |
A large-scale but short-term reduction in population size followed by an increase in population size. |
Hitchhiking/Selective Sweep |
Change in the frequency of an allele due to positive selection on a closely linked locus. |
Inbreeding |
Mating among kin. |
Inbreeding Depression |
Reduced fitness in individuals or populations resulting from kin matings; often due to the decrease in heterozygosity associated with kin matings, either because heterozygotes are superior or because homozygotes for deleterious alleles become more common. |
Identical by State |
If an allele within a single individual or many individuals that has the same nucleotide sequence. |
Identical by Descent |
Describes alleles, within a single individual or different individuals, that have been inherited from the same ancestral copy of the allele. |
Homozygous |
Having two alleles identical by state. |
Autozygous |
Having two alleles identical by descent. |
Zygotic Gene Flow |
Movement of an organism from one population to another. |