Genetic Diagrams

• Genetic Diagrams


  • They show the possible alleles of offspring
• Some characteristics are controlled by single genes
• Genes


  Control what characteristics you develop
• Alleles


  Different versions of genes
• Homozygous


  Organism has two alleles for a particular gene that are the same
• Heterozygous


  Organism has two alleles for a particular gene that are different
• Dominant allele


  Allele that determines the characteristic that is shown
• Recessive allele


  Allele that is not shown if the organism is heterozygous
• Genotype


  Combination of alleles an organism has
• Phenotype


  Characteristics an organism displays
• Monohybrid cross


  Breeding from two parents to look at just one characteristic
• Punnett square


  • Used to show genetic crosses
• Genetic diagrams only show probabilities, not definite outcomes
• Crossing a homozygous dominant hamster (BB) with a homozygous recessive hamster (bb)

  • All offspring are normal
• Crossing a cat with long hair (Hh) with a cat with short hair (hh)

  • Offspring have a 1:1 ratio of long and short hair
• Family tree


  Shows how characteristics are inherited
• Cystic fibrosis allele is not dominant, as carriers don't have the disorder
• New baby has a 25% chance of having cystic fibrosis and 50% chance of being a carrier