nonmedelian

• Inheritance


  The process of genetic transmission of traits from parents to offspring
• Mendelian Inheritance


  Inheritance that follows Mendel's laws
• Mendel's laws


  • Principle of segregation
  • Law of independent assortment
• Principle of segregation


  A given pair of alleles segregate randomly when gametes are formed
• Law of independent assortment


  Each pair of alleles will assort independently and randomly from every other pair of alleles
• Non-Mendelian Inheritance


  Natural deviations from Mendel's laws
• Types of non-Mendelian inheritance

  • Mendel's laws do not apply at all
  • Genotypic ratio is that expected from Mendel's laws but the phenotypic ratio is not
• Incomplete Dominance


  The heterozygotes have a different phenotype compared to the homozygotes, resulting in a blending of the parental phenotypes
• Codominance


  Both alleles of a gene pair are expressed in the phenotype of the organism
• Examples of codominance


  • Human blood groups
  • Coloration of Rhododendron flowers
• Multiple alleles/Polygenic Inheritance


  A single trait is controlled by multiple alleles and has many possible phenotypes, influenced by environmental factors
• Examples of multiple alleles/polygenic inheritance

  • Human blood groups
  • Height and eye color in humans
  • Fur color in animals

  
• Linked traits


  Traits passed down by genes located close to each other on the same chromosome, due to genetic linkage
• Example of linked traits


  • Red hair, fair skin and freckles in humans

  
• Sex-linked traits


  Linked traits with genes located on the same sex (X or Y) chromosome
• Example of sex-linked trait


  • Hemophilia
• Hemophilia is a recessive sex-linked trait that affects only males while females are generally carriers or have the normal phenotype

  
• The gene that codes for hemophilia is present only on the X chromosome

  
• In heterozygous females, the disorder is not expressed as the other normal X chromosome is expressed

  
• In males with a XC chromosome, the disorder will be expressed as the gene pair for the affected X chromosome will be a Y chromosome which does not have the normal gene to dominate over the affected X chromosome

  
• Hemophilia is passed down by the females of a bloodline and expressed usually in males