Genetic Diagrams

• What do genetic diagrams show?

  Combinations of alleles from two parents
• What does the dominant allele 'A' code for in mice?

  Normal amounts of average muscle
• What does the recessive allele 'a' code for in mice?

  Muscular mass
• How are alleles represented in genetic diagrams?

  As uppercase and lowercase letters
• What does a homozygous normal mouse's genotype look like?

  Capital A, capital A
• What is the phenotype of a homozygous muscular mouse?

  Muscular
• How do you find the gametes from a parent's genotype?

  Split the letters into separate circles
• What is the result of combining a capital A gamete with a lowercase a gamete?

  Capital A, lowercase a genotype
• What does it mean for offspring to be heterozygous?

  They have one allele of each type
• What is the phenotype of all heterozygous offspring in this example?

  Normal phenotype
• What is a Punnett square used for?

  To predict offspring genotypes and phenotypes
• How do you fill in a Punnett square?

  Combine gametes from both parents
• What is the ratio of normal to muscular mice from the heterozygous cross?

  3 to 1 ratio
• What is the probability of having muscular offspring from the heterozygous cross?

  One in four or 25%
• What is the genotype of the offspring when two heterozygous mice mate?

  One homozygous dominant, two heterozygous, one homozygous recessive
• What is the phenotype outcome when two heterozygous mice mate?

  Three normal and one muscular
• What are the five main steps to draw a genetic diagram?

  1. Identify parents' phenotypes and genotypes
  2. Determine gametes' genotypes
  3. Combine gametes to find offspring's genotypes
  4. Determine offspring's phenotypes
  5. Analyze results
• How do multiple genes and the environment affect traits?

  • Multiple genes interact to influence traits
  • Environmental factors can impact trait expression
  • Example: Nutrition and growth in height