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Allele frequency refers to how common an allele is in a population, expressed as a proportion or percentage of all alleles for a given gene. It is a fundamental concept in population genetics, influencing how genetic traits are passed on and how populations evolve over time.
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Heritability is a statistical estimate that measures the proportion of observed variation in a particular trait among individuals in a population that can be attributed to genetic differences. It is important to note that heritability does not indicate the extent to which a trait is genetically determined in an individual, nor does it imply immutability of the trait in response to environmental changes.
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Population genetics is the study of genetic variation within populations and involves the examination of changes in gene frequencies under the influence of evolutionary processes such as natural selection, genetic drift, mutation, and gene flow. It provides a genetic basis for understanding evolutionary biology and helps explain patterns of diversity and adaptation in natural populations.
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Mutation refers to a change in the nucleotide sequence of an organism's DNA, which can lead to variations in traits and potentially affect an organism's fitness. Mutations can occur spontaneously or be induced by environmental factors, and they play a crucial role in evolution and genetic diversity.
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Recombination is a genetic process where DNA strands exchange genetic material, leading to genetic diversity within a population. It plays a crucial role in evolution, repair of damaged DNA, and the proper segregation of chromosomes during meiosis.
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Natural selection is a fundamental mechanism of evolution where organisms better adapted to their environment tend to survive and produce more offspring. This process leads to the gradual adaptation of species to their environments over successive generations, driving the diversity of life on Earth.
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Genetic drift is a mechanism of evolution that results in random changes in allele frequencies within a population, often having a more pronounced effect in small populations. It can lead to the fixation or loss of alleles over time, independent of selective pressures, thus contributing to genetic diversity or homogeneity.
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Phenotypic variation refers to the differences in physical traits and characteristics among individuals of the same species, which arise from the interaction of genetic and environmental factors. Understanding Phenotypic variation is crucial for studying evolution, adaptation, and the genetic basis of traits in populations.
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Quantitative genetics is the study of how genetic and environmental factors influence complex traits that vary continuously, such as height or milk production. It involves statistical methods to estimate the genetic contribution to these traits and to predict the genetic potential of individuals based on their phenotype and pedigree information.
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Evolutionary biology is the study of the processes that have led to the diversity of life on Earth, focusing on the mechanisms of evolution such as natural selection, genetic drift, and gene flow. It integrates insights from genetics, paleontology, and ecology to understand how organisms adapt over time and how new species arise.
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Genetic architecture refers to the underlying genetic basis of a phenotypic trait, including the number, frequency, and effect sizes of genetic variants that contribute to the trait. It provides insights into how traits are inherited and can influence strategies for genetic research and breeding programs.
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Genomic selection is a modern breeding method that uses genome-wide genetic information to predict the breeding value of individuals, accelerating the selection process in plants and animals. This approach enhances the accuracy of selection by incorporating dense genetic markers, thus improving the efficiency and speed of breeding programs compared to traditional methods.
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Additive gene effects refer to the cumulative impact of individual alleles on a phenotype, where each allele contributes a fixed amount to the trait's expression. This concept is fundamental in quantitative genetics and helps in predicting offspring traits based on the sum of parental allele effects.
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A polygenic risk score (PRS) is a numerical value that quantifies an individual's genetic predisposition to a particular trait or disease based on the cumulative effect of multiple genetic variants. It enables personalized risk assessment and can inform prevention strategies and medical decision-making, though it is influenced by population-specific genetic data and environmental factors.
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Phenotypic variance refers to the variation in physical and physiological traits among individuals in a population, resulting from both genetic and environmental factors. It is a crucial component in understanding the heritability of traits and the potential for evolutionary change within a population.
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Epistatic variance refers to the portion of genetic variance attributed to interactions between different genes, rather than the additive effects of individual genes. This concept is crucial in understanding the complexity of genetic traits as it highlights how gene interactions can influence phenotypic expression, complicating predictions of trait inheritance.
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Dominance variance refers to the portion of genetic variance attributed to the interaction between alleles at the same locus, impacting the phenotype in a non-additive manner. This type of variance is crucial in understanding the inheritance patterns of traits, especially those that do not follow simple Mendelian inheritance due to the dominance relationships between alleles.
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Selection response is the change in the mean phenotype of a population as a result of selection, reflecting the genetic gain achieved per generation. It is a critical measure in evolutionary biology and breeding programs, indicating how effectively selection pressures translate into genetic improvement.
Genotype-environment interaction refers to the phenomenon where different genotypes respond differently to environmental variations, influencing the expression of traits. This interaction is crucial for understanding the complexity of traits, adaptation, and evolution in both natural and artificial selection contexts.
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Additive genetic variance is the portion of genetic variance that can be attributed to the additive effects of alleles, which directly impacts the heritability of a trait. It is crucial in predicting the response to selection in breeding programs, as it represents the genetic component that can be passed from parents to offspring.
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Breeding value estimation is a statistical approach used in genetics to predict the genetic potential of an individual as a parent, based on its own performance and the performance of its relatives. This estimation is crucial for selective breeding programs aimed at improving desirable traits in livestock, plants, or other organisms by choosing individuals with the highest predicted genetic merit.
Non-additive genetic variance refers to the portion of genetic variance that arises from interactions between alleles at different loci, such as dominance and epistasis, rather than the additive effects of individual alleles. This type of genetic variance is crucial for understanding the complexity of trait inheritance and evolution, as it can significantly influence phenotypic outcomes and response to selection.
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Effective population size is a measure of the genetic diversity of a population, reflecting the number of individuals who contribute genes to the next generation. It often differs from the actual population size due to factors like unequal sex ratios, variation in reproductive success, and fluctuating population sizes over time.
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Breeder's equation, R = h²S, is a fundamental formula in quantitative genetics that predicts the response to selection, where R is the response to selection, h² is the heritability, and S is the selection differential. It provides a framework for understanding how traits evolve under artificial or natural selection, assuming a linear relationship between phenotype and genotype.
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Narrow-sense heritability is the proportion of phenotypic variance in a population that is attributable to additive genetic variance, which can be passed from parents to offspring. It is crucial for predicting the response to selection in breeding and evolutionary studies, as it reflects the potential for a trait to evolve under natural or artificial selection.
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Broad-sense heritability is a measure of the proportion of phenotypic variance in a population that is attributable to genetic variance, including all genetic contributions such as additive, dominance, and epistatic effects. It provides an estimate of the genetic influence on a trait but does not distinguish between the different types of genetic variance, making it less precise for predicting response to selection compared to narrow-sense heritability.
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Non-additive genetic effects refer to the interactions between alleles at different loci or within the same locus that do not simply add up to influence a phenotype, often resulting in phenomena like dominance and epistasis. These effects can complicate predictions of trait inheritance and evolution, as they involve complex genetic interactions beyond simple Mendelian inheritance patterns.
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Additive variance is the portion of genetic variance attributed to the additive effects of alleles, which contribute to the resemblance between parents and offspring. It plays a crucial role in the response to selection in breeding programs, as it determines the potential for a population to evolve under selection pressure.
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Polygenic traits are characteristics influenced by multiple genes, often resulting in a continuous distribution of phenotypes, such as height or skin color. These traits are typically influenced by both genetic and environmental factors, making their inheritance patterns complex and multifactorial.
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Trait covariance refers to the statistical relationship between two or more traits within a population, indicating how changes in one trait are associated with changes in another. This concept is crucial for understanding the genetic and environmental factors that contribute to the variation and co-variation of traits in evolutionary biology and quantitative genetics.
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