NON-MENDELIAN INHERITANCE

• Alleles


  Two types of alleles exist for each gene
• Dominant allele


  Will always be expressed whenever present
• Recessive allele


  Will be expressed only in the absence of the dominant allele
• Mendel studied only simple or complete dominance patterns based on his work with pea plants
• Not all the traits they predicted followed the Mendelian patterns of inheritance
• Non-Mendelian genetics


  Inheritance patterns that deviate from Mendel's laws of inheritance
• Law of Segregation


  1. During the formation of gametes or sex cells, pairs of alleles segregate and then reunite at fertilization

  2. Each parent has two alleles for a specific trait but in the process of gene transmission, only one of those two alleles from each parent will be inherited by an offspring
• Law of Independent Assortment


  1. The segregation of genes during the formation of gametes occur independently

  2. An offspring inherits the traits of parents separately
• Law of Dominance


  1. In a pair of alleles, the dominant allele will mask the traits that the recessive allele carries

  2. Recessive traits can appear only if an individual inherits two copies of the recessive allele
• Non-Mendelian Patterns of Inheritance

  • Incomplete dominance
  • Codominance
  • Multiple alleles
  • Polygenes
  • Sex inherited traits