Concept 10: Segregation can be predicted based on independent assortment.
Mendel’s second law of inheritance was the principle of independent assortment. Mendel recognized that the traits he was following in peas each seemed to follow their pattern of segregation without regard to how other traits were being passed on. Making a prediction about combinations of two or more traits was a matter of simple probability. If the first trait had a ¼ chance of being inherited and the second trait had a ¼ chance, the probability of an offspring inheriting both traits was the product of each probability ( ¼ X ¼ = 1/16).
The reason for independent assortment lies in chromosome behavior. Genes that are on separate chromosomes are sent off to gametes independently because the chromosomes behave independently. Sexually reproducing organisms make lots of gametes and the combinations of gene in those gametes reflects the independent nature of the chromosomes.
The power of understanding these concepts is that they can be applied to predicting the inheritance of many different traits in many different sexually reproducing organisms. We will use several traits in plants as examples to provide some practice in working with these principles.