Genetic Diagrams & Punnet Squares

• 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 is a typical question regarding genetic diagrams?

  Draw a genetic diagram for two mice
• What are the five main steps to draw a genetic diagram?

  1. Identify parents' phenotype and genotype
  2. Determine gametes' genotypes
  3. Combine gametes to find offspring's genotypes
  4. Determine offspring's phenotypes
  5. Present the results in a diagram
• What is the genotype of a homozygous normal mouse?

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

  Muscular
• Why is the muscular allele expressed in a homozygous muscular mouse?

  Because it has two recessive alleles
• How do you find the gametes from a parent's genotype?

  Split the letters into separate circles
• What do you do to find the offspring's genotypes?

  Combine all possible gamete combinations
• What is the result of crossing a homozygous normal mouse with a homozygous muscular mouse?

  All offspring are heterozygous
• What phenotype do all heterozygous offspring exhibit?

  Normal phenotype
• What is a Punnett square used for?

  • To visualize genetic crosses
  • To show gamete combinations
  • To determine offspring genotypes and phenotypes
• How do you fill in a Punnett square?

  Place gametes on top and left
• What is the ratio of normal to muscular mice from two heterozygous parents?

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

  25 percent probability
• What happens when two heterozygous mice mate?

  • Offspring genotypes:
  • 1 homozygous dominant
  • 2 heterozygous
  • 1 homozygous recessive
  • Offspring phenotypes:
  • 3 normal
  • 1 muscular
• What factors can influence traits besides genes?

  Environmental factors like food and sleep
• What is the relationship between genes and environmental factors in determining traits?

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