Law of Independent Assortment

Our Objective

To verify Mendel’s Law of Independent Assortment.


The Theory

Law of independent assortment 

Gregor Johann Mendel also introduced the Law of independent assortment in 1865. He proposed that the different genes assorted independently into the gametes without affecting one another. The Law explains the principle of "how the different genes independently separate from one another in reproductive cells develop."  

He studied and performed a dihybrid cross in homozygous pea plants based on the morphological shape (round and wrinkled) and the colour of the seeds (yellow and green) and observed the parental traits' characters not always transferred in the offspring. He states, "when the two sets of traits of a dihybrid cross were segregate and one pair of character as independent of the other." He used the genotypic symbol of Y -dominant yellow seed colour, y - recessive green seed colour, R - round shaped seed colour, and r - wrinkled seed shape. He observed the results of the parental trait of RRYY and rryy. He studied the cross-pollination of RY and ry and addressed the gametes produced during the fertilization of F1 progeny as RrYy.   

After the self-pollination of the F1 progeny, he observed that the genes were independently assorting to one another without showing any dominant or recessive character. Based on the research, he found that a dihybrid cross gives the phenotypes as round, yellow: wrinkled, yellow: round, green: wrinkled, green, which appears in the ratio of 9:3:3:1.   


Fig. 1 Punnett square - Law of Independent assortment  

The Punnett square clearly explains the independent segregation of the parental gene exchange during meiosis and the production of eggs in the F1 RrYy plant.  The important point to remember here is, 50 % of the R and 50% of the r independently segregated with 50% of the Y and 50% of the y. Each trait has a 25% chance of the RY and Ry and  rY and Ry and it has independently assorted one another. The eggs and the pollen of the two sides were easy to derive the composition and produce the F2 plants independently.  


Learning Outcomes

  • Students can learn about the law of independent assortment.
  • Students can learn about the segregation arrangements.
  • Students can understand the Punnett square assortment.