Genetics

• Selective Breeding


  The crossing of desired traits from plants/animals to produce offspring with favourable characteristics
• Selective Breeding


  • Canola - germinates and grows rapidly in cold weather; extremely low in acid content
• Pedigree Chart


  A graphic flow chart of a family tree that shows patterns of inheritance that can be followed for a family for a single gene using symbols
• Pedigree Chart


  • It is a way to analyze how a trait 'runs in the family'
• Autosomal Inheritance


  The inheritance of traits whose genes are found on the autosomes (#1-22 in humans)
• Autosomal Dominant disorders


  The disease-causing allele is dominant
• Autosomal Recessive disorders


  The disease-causing allele is recessive
• Analyzing a pedigree can help determine whether the inheritance is autosomal dominant or recessive
• Autosomal Dominant


  • Affected individuals have dominant genotypes (AA or Aa)
  • If one parent has an abnormal gene and the other parent a normal gene, there is a 50% chance each child will inherit the abnormal gene, and therefore the dominant trait
  • EACH child has a 50:50 chance of inheriting the disorder
• Autosomal Dominant


  • Example 1 - if child is not affected, but both parents are affected
  • Example 2 - parents are affected I-1 and I-2 but some children are unaffected II-4 and II-5
• Autosomal Recessive


  • Affected individuals have recessive genotypes (aa)
  • 2 unaffected parents can have affected offspring 25% of the time
• Autosomal Recessive


  • Example 1 - Two unaffected parents can have an affected child IF both parents are carriers (heterozygote)
  • Example 2 - unaffected parents III-1 and III-2 have an affected children IV-1 and IV-2 and recessive trait can skip generations
• RULES OF INHERITANCE - Autosomal Dominant


  • Appears in both sexes with equal frequency
  • Both sexes transmit the trait to their offspring
  • Does not skip generations
  • Affected offspring must have an affected parent unless they posses a new mutation
  • When one parent is affected (het.) and the other parent is unaffected, approx. 1/2 of the offspring will be affected
  • Unaffected parents do not transmit the trait
• RULES OF INHERITANCE - Autosomal Recessive


  • Appears in both sexes with equal frequency
  • Trait tends to skip generations
  • Affected offspring are usually born to unaffected parents
  • When both parents are heterozygous approx. 1/4 of the offspring will be affected
• To Do List - Section 5.3 p. 223 #17-22, p. 227 #1-5, 7-12, Make your own note on Genetic Testing on pg. 224 (see Table 5.4), Pedigree Handout - Determine if autosomal recessive or dominant
• Gene Therapy - p. 226, Figure 5.18