Genetic Diagrams

• What do genetic diagrams show us?


  They show the different combinations of alleles from two parents.
• What does the dominant allele 'A' code for in the example of the mouse?


  It codes for normal amounts of average muscle.
• How is a recessive allele represented in genetic diagrams?


  It is represented as a lowercase letter.
• What is the genotype of a homozygous normal mouse?


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


  Lowercase a, lowercase a.
• Why is the muscular phenotype expressed in a homozygous recessive mouse?


  Because it has two recessive alleles.
• How do you find the gametes from the parents' genotypes?


  You split the two letters in each parent's genotype into separate circles.
• What do you do to find the offspring's genotypes from the gametes?


  You combine all possible combinations of the two parents' gametes.
• What is the result when a capital A gamete combines with a lowercase a gamete?


  The genotype will be capital A, lowercase a.
• What is the phenotype of all the offspring when crossing a homozygous normal mouse with a homozygous muscular mouse?


  All offspring will have the normal phenotype.
• What is a Punnett square used for?


  It is used to predict the genotypes and phenotypes of offspring.
• How do you set up a Punnett square for two heterozygous normal mice?


  You place capital A and lowercase a gametes on the top and left of the square.
• What are the possible genotypes of the offspring when two heterozygous normal mice mate?


  One homozygous dominant, two heterozygous, and one homozygous recessive.
• What is the phenotype ratio of normal to muscular mice from the cross of two heterozygous normal mice?


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


  There is a 1 in 4 or 25% probability.
• What are the five main steps to draw a genetic diagram?


  1. Identify the parents' phenotypes and genotypes.
  2. Determine the gametes' genotypes.
  3. Combine the gametes to find offspring's genotypes.
  4. Determine the offspring's phenotypes.
  5. Present the results clearly.
• What factors influence traits beyond single gene interactions?

  • Multiple genes interact
  • Environmental factors (e.g., nutrition, sleep)
• What is the significance of the uppercase letter in allele representation?


  It indicates a dominant allele.
• What is the significance of the lowercase letter in allele representation?


  It indicates a recessive allele.