Test 6

• Trait: a distinguishing characteristic or quality of an organism
• • Dominant gene/trait: upper case (A)
  • Recessive gene/trait: lower case (a)
• • Heterozygous: One of each allele, Aa
  • Homozygous: Two of the same allele, AA or aa
  • Homozygous dominant (AA): two dominant alleles
  • Homozygous recessive (aa): two recessive alleles
• • Genotype: the genetic make-up of a trait
  • Phenotype: the physical appearance of a trait
  • Testcross: a cross used to determine the genotype of an individual with the dominant phenotype
• Punnett Squares

  • Law of probability can predict Mendel’s results
• Mendel’s Laws of Heredity

  1. Law of Segregation
  2. Law of Independent Assortment
• • Polygenic inheritance: multiple genes are involved in controlling the phenotype of a trait
  • Continuous Variation: multiple genes act jointly to influence a quantitative trait
  • Height or weight
• • Pleiotropic: one gene affects many traits
  • Pleiotropy: one allele has more than one effect on the phenotype
• Phenotypic Considerations

  1. Incomplete dominance
  2. neither is dominate
  3. Environmental effects
  4. degree of allele expression may depend on the environment
  5. Epistasis
  6. products of some genes interact with each other and influence the phenotype
• Multiple Alleles

  • Codominance: no single allele is dominant, and each allele has its own effect (ex: AB Blood)
• • Pedigree: graphical representation of a gene through the generations
  • Mutations: accidental changes in genes