diff --git a/src/Chromosome.cpp b/src/Chromosome.cpp
index 1e40967..eae6a21 100644
--- a/src/Chromosome.cpp
+++ b/src/Chromosome.cpp
@@ -28,20 +28,10 @@ Chromosome::Chromosome()
 }
 
 
-Chromosome::Chromosome(Chromosome& father)
+Chromosome::Chromosome(const Chromosome& father, const Chromosome& mother)
 {
-	// reserve to father's size/capacity?
-	
-	for (auto& ptr : father.genes) {
-		this->genes.push_back(std::unique_ptr<Gene>(Gene::copy(ptr.get())));
-	}
-}
-
-
-Chromosome::Chromosome(Chromosome& father, Chromosome& mother)
-{
-	auto split_father = father.selectGene();
-	auto split_mother = mother.selectGene();
+	auto split_father = father.selectConstGene();
+	auto split_mother = mother.selectConstGene();
 	
 	// reserve to father's size/capacity, and shrink_to_fit afterwards?
 	
@@ -55,6 +45,30 @@ Chromosome::Chromosome(Chromosome& father, Chromosome& mother)
 }
 
 
+Chromosome::Chromosome(const Chromosome& other)
+{
+	// reserve to other's size/capacity?
+	
+	for (auto& ptr : other.genes) {
+		this->genes.push_back(std::unique_ptr<Gene>(Gene::copy(ptr.get())));
+	}
+}
+
+
+Chromosome& Chromosome::operator=(const Chromosome& other)
+{
+	// reserve to other's size/capacity?
+	
+	if (this != &other) {
+		for (auto& ptr : other.genes) {
+			this->genes.push_back(std::unique_ptr<Gene>(Gene::copy(ptr.get())));
+		}
+	}
+	
+	return *this;
+}
+
+
 void Chromosome::draw(sf::RenderTarget& target, sf::RenderStates states) const
 {
 	for (auto& geneptr : this->genes) {
@@ -100,6 +114,17 @@ std::vector<std::unique_ptr<Gene>>::iterator Chromosome::selectGene()
 }
 
 
+std::vector<std::unique_ptr<Gene>>::const_iterator Chromosome::selectConstGene() const
+{
+	if (genes.empty()) {
+		return this->genes.end();
+	} else {
+		std::uniform_int_distribution<> posdist(0, this->genes.size()-1);
+		return genes.begin() + posdist(*Chromosome::re);
+	}
+}
+
+
 void Chromosome::addGene()
 {
 	std::uniform_int_distribution<> typedist(0, this->allowedGeneTypes.size()-1);
diff --git a/src/Chromosome.hpp b/src/Chromosome.hpp
index b35a4cb..c1e69e2 100644
--- a/src/Chromosome.hpp
+++ b/src/Chromosome.hpp
@@ -18,8 +18,11 @@ public:
 	static bool isGeneTypeAllowed(Gene::GeneType gt);
 	
 	Chromosome();  // create empty chromosome
-	Chromosome(Chromosome& father);  // copy
-	Chromosome(Chromosome& father, Chromosome& mother);  // crossover
+	Chromosome(const Chromosome& father, const Chromosome& mother);  // crossover
+	
+	Chromosome(const Chromosome& father);  // copy constructor
+// 	Chromosome& operator=(const Chromosome& chr) = delete;  // copy assignment operator
+	Chromosome& operator=(const Chromosome& chr);  // copy assignment operator
 	
 	virtual void draw(sf::RenderTarget& target, sf::RenderStates states) const;
 	
@@ -33,6 +36,7 @@ private:
 	std::vector<std::unique_ptr<Gene>> genes;
 	
 	std::vector<std::unique_ptr<Gene>>::iterator selectGene();
+	std::vector<std::unique_ptr<Gene>>::const_iterator selectConstGene() const;
 	
 	void addGene();
 	void removeGene();