Lesson 18

• blending hypothesis


  old idea, genetic material from the two parents blends together
• particulate hypothesis


  idea that parents pass on discrete heritable units (genes)
• Gregor Mendel


  used scientific approach to identify two laws of inheritance, discovered basic principles of heredity
• character


  heritable feature that varies among individuals (ex: flower color)
• trait


  variant for a character (ex: purple or white)
• advantages of using peas


  short generation time, large numbers of offspring, mating could be controlled (self-pollinate or cross-pollinated)
• True-breeding


  plants that produce offspring of the same variety when they self-pollinate (phenotype)
• P generation


  true-breeding parents
• F1 generation 


  hybrid offspring of the P generation
• F2 generation


  produced when F1 individuals self-pollinate or cross-pollinate with other F1 hybrids
• Heritable factor


  is what we now call a gene
• Punnet Square


  possible combinations of sperm and egg
• Homozygote


  organism with two identical alleles
• Heterozygote

  organism with two different alleles for a gene
• An organism's traits do not always reveal its genetic composition
• Phenotype

  physical appearance
• Genotype

  genetic makeup