Independent assortment is a basic principle of genetics developed by a monk named Gregor Mendel
in the 1860's. Mendel formulated this principle after discovering another principle now known as Mendel's law of segregation
. This principle states that the alleles
for a trait separate when gametes are formed. These allele pairs are then randomly united at fertilization
. Mendel arrived at this conclusion by performing monohybrid crosses
. These were cross-pollination experiments with pea plants that differed in one trait, for example pod color.
Mendel began to wonder what would happen if he studied plants that differed in two traits. Would both traits be transmitted to the offspring together or would one trait be transmitted independently of the other? From his experiments Mendel developed the principle now known as the law of independent assortment.
Mendel's Law of Independent Assortment
Mendel performed dihybrid crosses
in plants that were true-breeding
for two traits. For example, a plant that had green pod color and yellow seed color was cross-pollinated with a plant that had yellow pod color and green seeds. In this cross, the traits for green pod color (GG) and yellow seed color (YY) are dominant. Yellow pod color (gg) and green seed color (yy) are recessive. The resulting offspring (Figure A)
or F1 generation
were all heterozygous
for green pod color and yellow seeds (GgYy).