Definition of Genetic Variability

Variability and Variation

The definition of genetic variability can be divided into two specific explanations. So, genetic variability is a term that can be used to define both of the following concepts:

• The difference in individual genotypes (and thus traits) within a population, and
• The rate at which a certain genotype can change in response to environmental or genetic factors.

It is important to note that variability is not the same as variation. Variability denotes how much a genotype tends to vary between individuals and in response to environmental and genetic factors, whereas variation is used to indicate the variation between and within species. Simply put, variability studies genotypes at the level of individuals and populations, and variation studies genotypes in and between species.

Measuring Genetic Variability

In general , variation is ‘easier’ to measure than variability. Some ways for measuring variation are, for example, describing phenotypic differences between organisms or populations, or using molecular markers to compare species or populations within a species.

As the definition of genetic variability has shown, variability is limited to a single population, making the measurement harder. Three commonly used methods to measure genetic variability are:

• Identifying different alleles: a certain gene can have different alleles. To illustrate this, consider a simplified gene for eye color which has a blue allele, a brown allele, a green allele, and so on. A high number of different alleles on the same locus (the place of the gene on the chromosome), increases the genetic variability.
• Determining the mutation rate: knowing how fast or how slow a certain gene mutates can help in assessing the rate at which a genotype can cope with new environmental or genetic stimuli. A high mutation rate means that the gene should be able to respond quickly to new circumstances, and this characterizes a high variability.
• Artificial selection experiments: another way to figure out how quickly a genotype responds to changes, is by putting study organisms through artificial selection, where the researchers controls the environmental variables. Logically, only organisms with a short life cycle are used for this (such as the fruit fly).

The Significance of Genetic Variability

A high genetic variation makes a healthy ecosystem or species. In the same way, a high genetic variability makes a healthy population. A higher variability means that the population is more able to respond to a change in their environment, and thus is more resistant to disease, climate change, competition from invading species, and so on.

As such, ensuring a high variability within a population will ensure that this population is better equipped to deal with change and foster their understanding of the definition of genetic variability.

References

• King, R.C.; Stansfield, W.D. & Mulligan, P.K. (2006). A Dictionary of Genetics, Seventh Edition. Oxford University Press.
• Maynard Smith, J. (1999). Evolutionary Genetics, Second Edition. Oxford University Press.
• Wagner, G.P. (1995). Adaptation and the Modular Design of Organisms. Advances in Artificial Life. 929, pp. 315 – 328.