EFFECT OF GENETIC DRAFT ON DIVERSITY
A Bit-String model
Genetic draft (or hitchhiking effect) occur when an allele changes frequency because it is near another gene that is undergoing a selective sweep.
The bit-string model presented explore effect of genetic draft on the natural variability in a population and consequences during environmetal changes.
SET OF PARAMETERS
Basics
A sequence of Amino Acid is represented by its lenght (AA). The model allow to modulate this number of positions (AA) and possibilities ( ie : number of type of Amino-Acids : A). The final fitness of each genotype is then evaluated depending of its Amino-Acid position across the sequence.
Fitness is evaluated from three life history traits :
Survival (S), depends of the environment.
Multiplication (M), capacity of multiplication of each genotype.
Quantity (Q), number of offsping.
The model simulate a finite population. The maximum of individuals (carrying capacity) is determined by Ge. Then the model will process evolution throught G generations.
The mutation rate (Txm) and maximum reproduction rate (M) are also defined by the user.
SET OF PARAMETERS
Fitness score
Each table represents the fitness of each Amino-Acid (20) and can be used to infer fitness at each position of the sequence.
Three examples are displayed, first where mutations are all neutral, second only one Amino-Acid is adaptative and the third example allow several adaptative solution.
To see the maximal diversity generated for a set of parameters, the model will run with all position without selection. In this case only the neutral fitness table will be used for each posisiotn of the sequence.
DIVERSITY ALONG THE BIT-STRING
Results example of the influence of each life history trait on the global diversity (the Shannon index can also be used).
Diversity for each position is calculated as : Unique AA at position x/Number of genotype.
​
Representation of the diversity : The diversity result is represented on a pie chart representing the 100 positions of the genome sequence.
​
Box A, present the maximal (all position neutrals) and minimal (all position under positive selection) diversity for specific parameters (see below). In B impact of the selecion of one history trait life on the diversity accross the genome (S,M or Q).
​
Parameters :
Tmx = 0,2
Carrying capacity = 150
Generation = 120
Sequence lenght = 100
​
​
