genetic diagrams

• Genetic diagram

  Diagram that shows the different combinations of alleles that can be inherited from two parents
• Allele


  Different versions of a gene
• Dominant allele

  Represented by a capital letter, expressed even if only one copy is present
• Recessive allele


  Represented by a lowercase letter, only expressed if two copies are present
• Homozygous


  Having two copies of the same allele
• Heterozygous


  Having one copy of each allele
• Phenotype


  The observable characteristics of an organism
• Genotype


  The genetic makeup of an organism
• Drawing a genetic diagram

  1. Find parents' phenotype and genotype

  2. Find gametes' genotypes

  3. Find offspring's genotypes

  4. Find offspring's phenotypes
• Genetic diagram example


  • Homozygous normal mouse x Homozygous muscular mouse
• Punnett square


  • Simpler to draw than genetic diagrams
  • Shows same information as genetic diagrams
• Using a Punnett square

  1. Place one parent's gametes on top

  2. Place other parent's gametes on left

  3. Fill in the squares with the combinations
• Punnett square example


  • Heterozygous normal mice x Heterozygous normal mice
• Normally loads of different genes interact and the outside environment can also play a big part in determining traits