AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

VALIDITY OF MENDEL'S FIRST AND SECOND PRINCIPLES

• Mendel’s first principle, the law of segregation, referring to the non-mixing of alleles in the hybrid and their subsequent segregation or separation in the gametes in equal frequencies, may be considered as the most important contribution of Mendel to heredity, since there no contrary experimental evidence as to the prevalence of any mixing of alleles in the hybrids.
  • So Mendel’s first law is universally applicable.
• Mendel’s second principle, the law of independent assortment referring to the separation of two pairs of alleles independently has only limited application, and hence cannot be considered as a universal law.
  • The second principle is valid only when two or more pairs of genes or alleles are situated in different chromosomes, enabling their independent assortment during the formation of gemetes.
  • This law has only limited applications when the genes are situated in the same chromosome.