Difference Between Law of Segregation and Law of Independent Assortment

Main Difference – Law of Segregation vs Law of Independent Assortment

Law of segregation and law of independent assortment are the first and the second laws of Mendelian inheritance. The law of segregation describes how alleles of a gene are segregated into two gametes and reunite after fertilization. The law of independent assortment describes how alleles of different genes independently segregate from each other during the formation of gametes. This is the main difference between law of segregation and law of independent assortment. 

Key Areas Covered

1. What is the Law of Segregation
      – Definition, Description and Explanation with Examples
2. What is the Law of Independent Assortment
      – Definition, Description and Explanation with Examples
3. What are the Similarities Between Law of Segregation and Law of Independent Assortment
      – Outline of Common Features
4. What is the Difference Between Law of Segregation and Law of Independent Assortment
      – Comparison of Key Differences

Key Terms: Alleles, First Law of Mendelian Inheritance, Genes, Law of Independent Assortment, Law of Segregation, Mendelian Inheritance, Phenotype, Second Law of Mendelian Inheritance

What is the Law of Segregation

The law of segregation is the first law of Mendel. It describes the separation of the two copies of the each hereditary factor during the production of gametes. Hence, the offspring may acquire one copy from each of the two parents. That means, the separated copies randomly unite during fertilization. The Mendel’s law of segregation shows that each hereditary unit or gene can exist in alternative forms. These alternative forms of a gene are called alleles. Each organism inherits two alleles of a particular trait. During the production of gametes, this allele pair separates in such a way that one gamete receives one allele of the pair. When the alleles in the pair comprise the same nucleotide sequence, these alleles are called homozygous alleles. But, if the nucleotide sequence of the two alleles in the pair is different, they are called heterozygous alleles. One allele in the heterozygous allele pair is dominant and the other allele is recessive. Only the dominant allele is expressed to produce the phenotype. This situation is referred to as complete dominance.

Figure 1: Inheritance of Red and White Flower Colors

For example, the gene, which is responsible for the color of a flower can be in two forms; red and white. The dominant form is A, which is responsible for the red color, while the recessive form a, which is responsible for the white flower color. The genotypes with the dominant allele, AA and Aa produce red color flowers. The genotype with the two recessive alleles produces white color flowers. The inheritance of red and white color flowers according to the law of segregation is shown in figure 1.

What is the Law of Independent Assortment

The second law of Mendel is the law of independent assortment. It describes the independent assortment of alleles of different genes. That means the transmission of different alleles of different genes is not affected by each other. This principle was formulated by performing a dihybrid crosses between plants with the two different traits. After performing a dihybrid cross, the ratio between the offspring will be 9:3:3:1. The inheritance of two characters, the pod color and the pod shape according to the law of independent assortment is shown in figure 2.

Figure 2: Inheritance of Pod Color and Pod Shape

Similarities Between Law of Segregation and Law of Independent Assortment

• Law of segregation and law of independent assortment describe the Mendelian inheritance patterns.
• Both laws describe the inheritance of alleles.
• Both segregation and the independent assortment are useful to increase diversity among individuals within a population.

Difference Between Law of Segregation and Law of Independent Assortment

Definition

Law of Segregation: Law of segregation is a principle described by Gregor Mendel in which the two copies of each of the hereditary factor segregate from each other during the production of gametes.

Law of Independent Assortment: Law of independent assortment is a principle described by Gregor Mendel in which the individual hereditary factors are independently assorted during the production of gametes when two or more factors are inherited.

Mendelian Inheritance

Law of Segregation: The law of segregation is the first law of Mendelian inheritance.

Law of Independent Assortment: The law of independent assortment is the second law of Mendelian inheritance.

Behavior

Law of Segregation: Law of segregation describes the behavior of nonhomologous chromosomes.

Law of Independent Assortment: Law of independent assortment describes the behavior of alleles.

Ratio of Offspring

Law of Segregation: The ratio between the offspring is 3:1.

Law of Independent Assortment: The ratio between the offspring is 9:3:3:1.

Conclusion

Law of segregation and law of independent assortment are the two laws that describe the inheritance of alleles. The law of segregation describes how alleles of a gene are segregated into two gametes and reunite after fertilization. The law of independent assortment describes how alleles of different genes independently segregate from each other during the formation of gametes. The main difference between the law of segregation and law of independent assortment is in the origination of alleles, which segregate during the formation of gametes.

Reference:

1. Bailey, Regina. “The 4 Concepts Related to Mendel’s Law of Segregation.” ThoughtCo. N.p., n.d. Web. Available here. 10 Aug. 2017.
2. “Mendels Law of Independent Assortment – Boundless Open Textbook.” Boundless. N.p., 26 May 2016. Web. Available here. 10 Aug. 2017. 

Image Courtesy:

1. “Mendel 2 miguelferig” By Miguelferig – Own work (CC0) via Commons Wikimedia
2. “Independent assortment & segregation” By LadyofHats – Own work (Public Domain) via Commons Wikimedia