NetLogo User Community Models

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## WHAT IS IT?

This model simulates fluctuactions of two alleles over time (measured in generations). The alleles are ideally taken from a single autosomic and biallelic locus of a diploid organism. The model is focused on showing a sequence of generations, each of them with its own genetic composition, from the point of view of alleles only, without any representation of the organisms that "transport" them.

## HOW IT WORKS

In this model, each allele makes a copy of itself for each generation (considering two random paired alleles from the current population, this passage represents the formation of four gametes from an original diploid cell), but only one half of the four possible gametes produced in each cycle is randomly chosen to pass to the next generation, in the form of an abstract zygote which is graphically represented by links. This means that each individual of each ideal couple of organisms containing these alleles passes two gametes to the next generation, so two new individuals are generated (while parents die). The whole process is iteratively repeated, while the total number of alleles is always kept constant. Note that the spatial element is totally irrelevant here: close alleles are not related each other.

## HOW TO USE IT

Use the SLIDERS to choose the initial numbers of the two alleles, then click on SETUP to visualize a circular composition of the alleles in the empty space of the world. You can proceed with a discrete mode by clicking first on "CREATE-GAMETES", then to "CREATE-ZYGOTES", or you may prefer to perform this alternation automatically by clicking on "GO".

## THINGS TO NOTICE

Note that the monitor GENERATION is updated after each cycle of meiosis and fertilization, and that these processes have to be executed alternately so as not to compromise the count. Furthermore, the total number of alleles for each simulation should always be even, in order to maintain the behavior of the system compatible with an evolving diploid population.

## THINGS TO TRY

Try to set different initial numbers for each allele and observe how the total number of alleles and the allele frequencies (p and q) influence the final outcome of each simulation. Random genetic drift effects may be easily noted.

## EXTENDING THE MODEL

The model may be extended by allowing fluctuations in the total number of alleles, thus considering population growth and decrease.

## NETLOGO FEATURES

Alleles' coupling is accomplished thanks to the use of the "homologous" property (and implemented with a turtles-own). Zygotes are created with the command "create-link-with".

## RELATED MODELS

Hardy Weinberg Equilibrium, GenEvo 2 Genetic Drift.

## CREDITS AND REFERENCES

For the model itself:

Tarantino, R. (2021). Evolving Allele Population.

Please cite the NetLogo software as:

Wilensky, U. (1999). NetLogo. http://ccl.northwestern.edu/netlogo/. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.