Non-Mendelian Genetics

• Chromosomes 


  They contain the genes.

  
• Genes

  are segments of DNA located on chromosomes that determine an organism's various characteristics and traits.

  
• Allele


  Different version of genes.
• Homozygous has two identical alleles for a specific gene (BB or bb)

  
• Heterozygous has two different alleles for a particular gene. (Bb)

  
• Dominant


  Only ONE allele is needed for the trait to be expressed. B (Brown eyes)
• Recessive


  TWO alleles are required for the trait to be expressed. b (blue eyes)
• Mendelian Genetics

  Dominant alleles masked the recessive alleles.
• Non-Mendelian Genetics

  1. In some cases, neither allele is completely dominant over the other.
  2. Some traits are controlled by multiple alleles.
  3. Certain traits are more prevalent or expressed differently in one sex compared to the other.
• Incomplete Dominance

  • In some cases, one allele will not be completely dominant over the other allele.
  • Results in a blending of the two alleles.

  
• Codominance


  • In some cases, both alleles are dominant and expressed at the same time.
  • Generally results in a spotted appearance.

  
• Female: XX
• Male: XY
• Sex-linked Traits

  • genetic traits that are determined by genes located on the sex chromosomes.
  • Usually found on the X chromosome.
  • X-linked alleles are always expressed in males because males have only one X chromosome.
• Multiple Alleles


  • In some cases, more than just 2 alleles exist in the population.
  • The gene is said to have multiple alleles.