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Phenotypic variation is caused by a combination of genetic and environmental factors. Genetic factors, such as DNA mutations and gene expression, contribute to differences in physical characteristics between individuals. Environmental factors, such as diet, stress, and exposure to toxins, can also influence how genes are expressed and contribute to phenotypic variation.
Human genetic variation is the genetic diversity of humans and represents the total amount of genetic characteristics observed within the human species. Genetic differences are observed between humans at both the individual and the population level. There may be multiple variants of any given gene in the human population (alleles), leading to polymorphism. Many genes are not polymorphic, meaning that only a single allele is present in the population: that allele is then said to be fixed.[1]
No two humans are genetically identical. Even monozygotic twins, who develop from one zygote, have infrequent genetic differences due to mutations occurring during development and gene copy number variation has been observed.[2] Differences between individuals, even closely related individuals, are the key to techniques such as genetic fingerprinting. Alleles occur at different frequencies in different human populations, with populations that are more geographically and ancestrally remote tending to differ more.
Causes of differences between individuals include the exchange of genes during meiosis and various mutational events. There are at least two reasons why genetic variation exists between populations. Natural selection may confer an adaptive advantage to individuals in a specific environment if an allele provides a competitive advantage. Alleles under selection are likely to occur only in those geographic regions where they confer an advantage. The second main cause of genetic variation is due to the high degree of neutrality of most mutations. Most mutations do not appear to have any selective effect one way or the other on the organism. The main cause is genetic drift, this is the effect of random changes in the gene pool. In humans, founder effect and past small population size (increasing the likelihood of genetic drift) may have had an important influence in neutral differences between populations.
The theory that humans recently migrated out of Africa is sometimes given as an example of this. It has been theorized that the population which migrated out of Africa only represented a small fraction of the genetic variation in Africa, and that this is a contributing cause of the observed lower levels of diversity in all indigenous humans outside of Africa. Generally, more recent neutral polymorphisms caused by mutation are likely to be relatively geographically localized and rare, while older polymorphisms are more likely to be shared by a wider range of human groups. The large majority of observed genetic variation occurs within a population in any geographic region and not between populations in different regions, although it is still usually possible to accurately identify the geographic origins of any individual's ancestors by genetic means.
The study of human genetic variation has both evolutionary significance and medical applications. The study can help scientists understand ancient human population migrations as well as how different human groups are biologically related to one another. From a medical perspective the study of human genetic variation may be important because some disease causing alleles occur at a greater frequency in people from specific geographic regions.
A few factors, mainly crossing-over in meiosis, random fertilization, and random separation of sister chromosomes in meiosis. There are also mutations, though they tend to have less of an impact of phenotypes.
Combination of genotype and edaphic factors or environmental factors
Genotypic variation occurs when alleles are randomly sorted during sexual reproduction.
Variation in phenotype expression is caused by 3 things: Age, Environment, and Interaction with other genes in the genotype.
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What causes varation in traits?
Genotypic variation is caused by mutation. Phenotypic variation can be caused by mutation, which gives rise to different alleles, or it can be caused by environmental factors.
A bell shaped curve of phenotypic variation is a representation of?
A bell shaped curve of phenotypic variation is a graphical representation of the distribution of a trait within a population. It shows that most individuals in the population have an average value for the trait, with fewer individuals on the extreme ends of the spectrum.
Brown eyes blue eyes and green eyes are an example of?
These eye colors are phenotypic expression of genotypes for eye color.
What are causes of variation in quality?
Causes of variation in quality can include differences in raw materials, production processes, equipment maintenance, employee training, and quality control measures. Variations in these factors can result in inconsistencies in product quality.
What are some of the phenotypic variations that are possible with codominance?
In codominance, both alleles are expressed fully in the heterozygous individual. This results in a phenotype where both traits are visibly expressed, rather than blending together. An example of codominance is when a red flower and a white flower produce offspring with red and white patches.
What causes varation in traits?
Genotypic variation is caused by mutation. Phenotypic variation can be caused by mutation, which gives rise to different alleles, or it can be caused by environmental factors.
A bell shaped curve of phenotypic variation is a representation of?
A bell shaped curve of phenotypic variation is a graphical representation of the distribution of a trait within a population. It shows that most individuals in the population have an average value for the trait, with fewer individuals on the extreme ends of the spectrum.
Which cross would produce the least phenotypic variation?
There are two choices that produce the least phenotypic variation. AA times aa produces only Aa offspring. AA times Aa produces and AA and Aa offspring.
What are the two types of variation shown by living organisms?
The two types of variation shown by living organisms are genetic variation, which is differences in DNA sequences among individuals, and phenotypic variation, which refers to observable traits or characteristics that vary among individuals.
What causes the variation in pitch?
it is caused when the variation is hit on the guitar
Brown eyes blue eyes and green eyes are an example of?
These eye colors are phenotypic expression of genotypes for eye color.
Difference between broad sense heritability and narrow sense heritability?
Broad-sense heritability includes all sources of genetic variance, both additive and non-additive, in a population, while narrow-sense heritability only considers additive genetic variance. Narrow-sense heritability is a more precise measure of the proportion of phenotypic variance that can be attributed to additive genetic effects.
What kind of variation must exist in a population that has a wide range of phenotypes?
Genetic variation must exist within the population, meaning individuals have different alleles. This genetic diversity results in a wide range of phenotypes that can be observed. Environmental factors can also contribute to phenotypic variation within the population.
What causes variation of traits in a population?
the enviroment.
What modes of selection leads to a reduction in variation but no change in the mean?
Stabilizing selection is the mode of selection that can lead to a reduction in variation without changing the mean of a trait. In this type of selection, extreme phenotypes are selected against, while intermediate phenotypes are favored, resulting in a narrower range of phenotypic variation but maintaining the same mean.
What is a heritable feature?
A heritable feature is a trait that is passed down from parents to offspring through their genes. These features can include physical characteristics, behaviors, and susceptibilities to certain diseases.
What is phenotypic variation?
Phenotype variation is slight variations in a phenotype that are caused by the expression of an organism's genes or the influence of environmental factors. A species can have several different phenotypes within it.
