Science 8

• Mendelian Genetics


  Genetics named after Gregor Mendel
• Gregor Mendel made huge advances in the field of genetics
• Gregor Mendel crossed pea plants and studied the offspring
• Peas


  Have a number of different characteristics and can be grown quickly to study genetics
• Mendelian Genetics


  Simple genetics, following the laws of segregation and independent assortment
• Mendel's Laws


  • Law of Segregation
  • Law of Independent Assortment
• Mendel's Law of Segregation


  Genes separate randomly during gamete formation, 50% chance of inheriting each allele
• Mendel's Law of Independent Assortment

  Traits are inherited independently, not influenced by each other
• Linked genes on the same chromosome are inherited together, not covered in this lesson
• Coin flip


  • 50% chance of heads or tails
• Traits


  • Hitchhiker's thumb
  • Attached earlobe
• Some traits are linked, like red hair and freckles, but not covered in this lesson
• Homozygous


  Having two identical alleles for a trait
• Heterozygous


  Having two different alleles for a trait
• Homozygous


  Having the same alleles for a particular trait
• Heterozygous


  Having different alleles for a particular trait
• Genotype


  The genetic makeup of an organism
• Phenotype


  The physical appearance or observable characteristics of an organism
• Monohybrid cross


  1. Punnett square

  2. Probability calculations
• Huntington's Disease is a dominant genetic disorder that causes degeneration of nerve fibers in the brain
• Huntington's Disease symptoms appear in middle age and the disease is often passed on before symptoms manifest
• If a parent has Huntington's Disease (big H little h)


  Their offspring have a 1 in 2 probability of inheriting the disease
• Genetic testing for Huntington's Disease raises ethical issues around insurance coverage and life planning