Reproductive recombination and genetic mutation.
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 is confusing go eat a dragon
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.
Mutations
Gamete formation
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.
continuous variation.
Blending or mixing of the colors is a phenotypic variation that is possible with co-dominance. Seeing both colors present at the same time is also possible.
system failure
Causes of variation is random mutation. Random mutations constantly occur in the genomes of organisms; these mutations create genetic variation. If all living things were same, we will all use up one type of food as our nutrient source and eventually we will run out of food to consume.. making less likely for us to survive..
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.
continuous 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.
Blending or mixing of the colors is a phenotypic variation that is possible with co-dominance. Seeing both colors present at the same time is also possible.
Broad sense heritability A.K.A (H) is the degree in which phenotypic variation is due to genetic factors Narrow sense heritability A.K.A (h) is the degree in which phenotypic variation is due to additive genetic factors. in maths terms... H = Vg/Vt h = Va/Vt Vg= genetic varaition Vt = total variation Va = additive variation
Gregor Mendel was the father of heredity. His experiments with pea plants established principles of dominance and recessiveness in phenotypic variation.
it is caused when the variation is hit on the guitar
Heritability is the proportion of Phenotypic variation in a population that is attributable to genetic variation among individuals. Phenotypic variation among individuals may be due to genetic and/or enviromental factors. Heritability analyses estimate the relative contributions of differences in genetic and non-genetic factors to the total phenotypic variance in a population.
Look at a population of humans. Your class will do. Now, how many different heights, hair colors and other assorted phenotypic variations can you see in this small population?This is the frequency of alleles of these types that we call natural variation.
the enviroment.
The ozone layer
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.