Corn Genetics Lab Notes

Corn Genetics Lab Exercise

Introduction

  • A self-fertilized green corn plant produced offspring including many white (albino) seedlings.

  • The lab exercise involves analyzing the offspring of this self-fertilization to determine the inheritance pattern of the mutation and the parent plant's genetic makeup for this trait.

Materials

  • One planting box

  • One plastic bag

  • 30 soaked/germinating corn seeds

  • Soil

Procedure

  1. Labeling the Planting Box:

    • Write name, date, and lab day on the planting box using a marker.

  2. Adding Soil:

    • Add a layer of soil to the planting box.

  3. Moistening the Soil:

    • Add water to the soil to moisten it.

  4. Planting Seeds:

    • Plant 30 seeds in the soil and cover them with approximately 5 mm of soil.

  5. Creating a Moist Environment:

    • Place the planting box inside a plastic bag to maintain soil moisture.

    • Store the box in a location specified by the instructor, ideally at room temperature (20−25°C20-25°C) and away from direct sunlight.

  6. Initial Observation:

    • After one week, remove the plastic bag and water as necessary.

    • Seedlings should be visible.

  7. Phenotype Determination:

    • After two weeks, identify the phenotypes of the seedlings.

    • Record the number of seedlings for each phenotype on the data sheet.

  8. Class Data:

    • Obtain class data and record it on the data sheet.

Chi Square Test

  • Used to compare expected and observed results in genetics experiments.

  • Observed results often do not perfectly match expected Mendelian ratios.

  • Differences can arise due to chance or other influencing factors.

  • Chi-Square test, or Goodness of Fit test, helps determine if the differences are statistically significant.

Calculating Expected Results

  • Example: Trait determined by a single gene pair with dominant-recessive inheritance.

  • Cross: Two Drosophila with long-winged phenotypes.

  • F1 generation: 62 progeny with long wings, 15 with vestigial (short) wings.

  • Observed result: 62 long wings, 15 vestigial wings.

  • Conclusion: Parents are heterozygous for wing type, carrying a non-expressed gene.

  • Punnett square is used to determine the expected result.

  • Expected result: 75% long wings, 25% vestigial wings.