How does inherited variation occur

Genes are small sections of DNA within the genome that code for proteins. They contain the instructions for our individual characteristics — like eye and hair colour. Inheritance is the process by which genetic information is passed on from parent to child. This is why members of the same family tend to have similar characteristics. In biology, evolution is the change in the characteristics of a species over several generations and relies on the process of natural selection.

A mutation is a change that occurs in our DNA sequence, either due to mistakes when the DNA is copied or as the result of environmental factors such as UV light and cigarette smoke. If you have any other comments or suggestions, please let us know at comment yourgenome. Can you spare minutes to tell us what you think of this website?

Open survey. In: Facts In the Cell. Other new alleles may be immediately detrimental such as a malformed oxygen-carrying protein and organisms carrying these new mutations will die out. Neutral alleles are neither selected for nor against and usually remain in the population. Genetic variation is advantageous because it enables some individuals and, therefore, a population, to survive despite a changing environment.

Some species display geographic variation as well as variation within a population. Geographic variation, or the distinctions in the genetic makeup of different populations, often occurs when populations are geographically separated by environmental barriers or when they are under selection pressures from a different environment.

One example of geographic variation are clines: graded changes in a character down a geographic axis. Gene duplication, mutation, or other processes can produce new genes and alleles and increase genetic variation.

Consequently, genetic variation is often considered an advantage, as it is a form of preparation for the unexpected. But how does genetic variation increase or decrease? And what effect do fluctuations in genetic variation have on populations over time? Mating patterns are important. Random forces lead to genetic drift. If the individuals at either end of the range reconnect and continue mating, the resulting genetic intermixing can contribute to more genetic variation overall.

However, if the range becomes wide enough that interbreeding between opposite ends becomes less and less likely, and the different forces acting at either end become more and more pronounced, and the individuals at each end of the population range may eventually become genetically distinct from one another.

Here is an example of migration affecting relative allele frequency:. The overall effect. Here is an example of how a specific genotype is less favorable than another genotype:. Genetic variation in a population is derived from a wide assortment of genes and alleles. The persistence of populations over time through changing environments depends on their capacity to adapt to shifting external conditions.

Sometimes the addition of a new allele to a population makes it more able to survive; sometimes the addition of a new allele to a population makes it less able. Still other times, the addition of a new allele to a population has no effect at all, yet the new allele will persist over generations because its contribution to survival is neutral. Key Questions How can genetic variation influence evolution?

What is an example of genetic drift? Topic rooms within Genetics Close. No topic rooms are there. Browse Visually. Other Topic Rooms Genetics. Student Voices.

There are many reasons nonrandom mating occurs. One reason is simple mate choice or sexual selection; for example, female peahens may prefer peacocks with bigger, brighter tails. Traits that lead to more matings for an individual lead to more offspring and through natural selection, eventually lead to a higher frequency of that trait in the population. Assortative mating in the American Robin : The American Robin may practice assortative mating on plumage color, a melanin based trait, and mate with other robins who have the most similar shade of color.

However, there may also be some sexual selection for more vibrant plumage which indicates health and reproductive performance. Another cause of nonrandom mating is physical location. This is especially true in large populations spread over large geographic distances where not all individuals will have equal access to one another.

Some might be miles apart through woods or over rough terrain, while others might live immediately nearby. Genes are not the only players involved in determining population variation. Phenotypes are also influenced by other factors, such as the environment.

A beachgoer is likely to have darker skin than a city dweller, for example, due to regular exposure to the sun, an environmental factor. Some major characteristics, such as gender, are determined by the environment for some species. For example, some turtles and other reptiles have temperature-dependent sex determination TSD.

TSD means that individuals develop into males if their eggs are incubated within a certain temperature range, or females at a different temperature range. Temperature-dependent sex determination : The sex of the American alligator Alligator mississippiensis is determined by the temperature at which the eggs are incubated. Eggs incubated at 30 degrees C produce females, and eggs incubated at 33 degrees C produce males.

Geographic separation between populations can lead to differences in the phenotypic variation between those populations. Such geographical variation is seen between most populations and can be significant. One type of geographic variation, called a cline, can be seen as populations of a given species vary gradually across an ecological gradient. Geographic variation in moose : This graph shows geographical variation in moose; body mass increase positively with latitude.

This is considered a latitudinal cline. Alternatively, flowering plants tend to bloom at different times depending on where they are along the slope of a mountain, known as an altitudinal cline.

If there is gene flow between the populations, the individuals will likely show gradual differences in phenotype along the cline. Restricted gene flow, on the other hand, can lead to abrupt differences, even speciation. Privacy Policy. Skip to main content. The Evolution of Populations. Search for:. Population Genetics. Genetic Variation Genetic variation is a measure of the variation that exists in the genetic makeup of individuals within population.

Learning Objectives Assess the ways in which genetic variance affects the evolution of populations. Key Takeaways Key Points Genetic variation is an important force in evolution as it allows natural selection to increase or decrease frequency of alleles already in the population. Genetic variation is advantageous to a population because it enables some individuals to adapt to the environment while maintaining the survival of the population. Key Terms genetic diversity : the level of biodiversity, refers to the total number of genetic characteristics in the genetic makeup of a species crossing over : the exchange of genetic material between homologous chromosomes that results in recombinant chromosomes phenotypic variation : variation due to underlying heritable genetic variation ; a fundamental prerequisite for evolution by natural selection genetic variation : variation in alleles of genes that occurs both within and among populations.