calling a function for mutation operator but getting error

I am calling following function, but getting error (Undefined function or variable 'parent_genotype')

genotype = mutation_new(parent_genotype,mutation_rate,n_genes_mutated,total_jobs);

data in mutation_new.m file is as under

function genotype = mutation_new(parent_genotype,mutation_rate,n_genes_mutated,total_jobs)

population_size = 5;
mutation_rate = 0.1;
total_jobs=50;
parent_genotype = randperm(total_jobs);
b = parent_genotype;
population_matrix = zeros(population_size,total_jobs); 
n_genes_mutated = length(parent_genotype)*mutation_rate;

for  i = 1:n_genes_mutated/2
    num1 = randi(total_jobs,1);
    num2 = randi(total_jobs,1);
    b([num1 num2]) = b([num2 num1]);    
end
genotype = b;