How to assess genetic biodiversity

Genetic biodiversity can be assessed by calculating the percentage of gene variants (alleles) in a genome within isolated populations.

A high genetic biodiversity means there is a large variety of alleles in the population's gene pool. This increases a population's ability to adapt to environmental changes, and so helps them avoid extinction.

How to calculate the proportion of polymorphic gene loci

A polymorphic gene is when a gene locus has multiple alleles. A monomorphic gene is one where a single allele exists, keeping the basic structure of individuals in a species consistent.

The proportion of polymorphic gene loci measures diversity: a higher proportion of polymorphic gene loci means there is a greater genetic diversity.

It is calculated as follows:

$\text{proportion of polymorphic gene loci }=\frac{\text{number of polymorphic loci}}{\text{total number of loci}}$

Worked example - Calculating the proportion of polymorphic loci

A geneticist is studying a population of beetles and has identified a total of 50 loci. Out of these, 18 loci are found to be polymorphic.

Calculate the proportion of polymorphic gene loci in the beetle population.

Step 1: Equation

$\text{proportion of polymorphic gene loci }=\frac{\text{number of polymorphic loci}}{\text{total number of loci}}$

Step 2: Substitution and correct evaluation

$\text{proportion of polymorphic gene loci }=\frac{18}{50}$

$\text{proportion of polymorphic gene loci }=0.36$

this means that 36% of the loci are polymorphic

How genetic diversity can change

Genetic diversity is not static. It can increase or decrease in populations and species over time.

Genetic biodiversity of a population can be increased by:

1. Gene flow - This is interbreeding between different populations, introducing new alleles.
2. Mutations in the DNA of an organism - This creates new alleles.

Genetic biodiversity of a population can be decreased by:

1. Selective breeding - Humans choose organisms with advantageous characteristics to breed (e.g. for rare dog breeds).
2. Captive breeding programmes - A small group of individuals are bred in captivity.
3. Artificial cloning - Using asexual reproduction to artificially produce large numbers of a particular (e.g. cloning crop plants).
4. Natural selection - Species evolve and advantageous characteristics increase in a population.
5. Genetic bottlenecks - A sudden decrease in population size means only a few individuals remain.
6. The founder effect - A few individuals form a new population split from the original one.
7. Genetic drift - Alleles are randomly passed through generations and some may disappear by chance.

Note: You will learn more about these processes in more detail in later lessons.