On this page
In This Article
What is genetic variation?
- Genetic variation refers to the diversity in DNA sequences among individuals within a population. This variation arises from several biological mechanisms and plays a crucial role in the adaptability and evolution of species. Understanding genetic variation is essential for both students and educators in biology, as it forms the foundation for many concepts in genetics and evolutionary theory.
- At its core, genetic variation results from differences in alleles, which are alternative forms of genes. Each organism inherits a unique combination of alleles from its parents, leading to distinct traits such as height, skin tone, or susceptibility to certain diseases. The phenotypic expression of these traits—the observable characteristics—can be influenced not only by genetic factors but also by environmental conditions. For example, two plants of the same species might exhibit different heights due to varying access to water and nutrients. Therefore, the phenotypic variation observed in a population is a product of both genetic and environmental influences.
- To isolate the impact of genetic factors, one must consider the
Vad är mutationer?
Mutationer är förändringar i DNA-sekvensen som uppkommer spontant i alla livsformer och i alla generationer. Om mutationerna uppstår i en gen eller ett så kallat reglerelement så kan de ge upphov till nya egenskaper.
Om mutationen ökar bärarens chanser att överleva och föröka sig kan den över tid spridas och bli vanlig i en population. Hos arter med sexuell reproduktion måste mutationen finnas i en könscell för att kunna föras vidare till nästa generation. När mutationer uppkommer i somatiska celler, ärvs de visserligen vidare till andra celler vid celldelningen, men stannar i individen. Det kallas för somatiska mutationer.
Så här uppstår mutationer
Kopieringsfel inne i cellen
En cell delar sig ett antal gånger under sin livstid. På så sätt bildas hela tiden nya celler i kroppen som kan ersätta gamla eller skadade celler. Inför varje celldelning kopieras allt DNA så att det i alla celler finns en kopia av individens genom. Ibland uppstår det fel vid kopieringen. Oftast lyckas cellen la
Understanding Evolution
Without genetic variation, some key mechanisms of evolutionary change like natural selection and genetic drift cannot operate.
There are three primary sources of new genetic variation:
- Mutations are changes in the information contained in genetic material. (For most of life, this means a change in the sequence of DNA.) A single mutation can have a large effect, but in many cases, evolutionary change is based on the accumulation of many mutations with small effects.
- Gene flow is any movement of genetic material from one population to another (e.g., through migration) and is an important source of genetic variation.
- Sex can introduce new gene combinations into a population. This genetic shuffling is another important source of genetic variation.
Genetic variation refers to variation (change or difference) of the gene among the members of the same species or individuals.
Genotype is the total sum of genetic determinants carried by a cell that is transmitted from generation to generation. Genotype is determined by the genetic information contained in the entire DNA content of the genome in the chromosome.
Genes carry instructions that are used for building protein. Differences in DNA sequence or gene between individuals are also known as genetic variations, and each variation of a gene is called an allele.
Genetic variation occurs in entire species, known as genetic diversity. Genetic variation is essential for the natural selection process because natural selection can only decrease or increase the allelic frequency already present in the population.
Genetic variation plays an advantageous role in the population because it favors some individuals to adapt to the environment. Mutation, gene flow, sexual reproduction, random mating between organisms, random fertilization, and crossing over are the main cause of genetic variation. Genetic variation along with environmental variation causes phenotypic variation in a
.