Biology 1-2Name:Per:

“Inheriting the gene for GREEN”-

Investigating Patterns of Inheritance

RESEARCH PROBLEM: Which forms of the “green gene” were possessed by the “parents” of our seedlings?

INTRODUCTION: The seeds you are planting represent the offspring (embryos) of two parents of a single cross. Remember, that every living thing (including plants) has two copies of each gene because it has two parents. The two genes have the instructions for making a protein which gives us a particular trait. The trait we will study in this genetics experiment is CHLOROPHYLL PRODUCTION. There are two form of the gene for this trait: G = the gene for making chlorophyll and being green and g = the gene for NOT making chlorophyll and being albino. (NOTE: pay close attention to the symbols used for each form of the trait. What does this tell us about the pattern of inheritance?????)

By planting our seeds and counting the number of green and albino seedlings, we can figure out the genetics of our seedlings’ parents.

MATERIALS (per team): corn seeds of known genetic parentage (about 6-7 seeds), a paper cup, potting soil, a marking pen

PROCEDURE

  1. Obtain a paper cup.
  2. Label it with your name and class period.
  3. Poke 3 SMALL holes in the bottom for drainage.
  4. Fill the cup about ¾ full with moist potting soil
  5. Obtain your allotment of corn seeds (about 6-7).
  6. Poke a hole in the potting soil about ½ inch deep and drop in a corn seed. Cover the seed over.
  7. Repeat until all of your seeds have been planted.
  8. Water your seeds just until moist (you should avoid soaking the soil—you don’t want water running out of the bottom of the cup!!!).
  9. Place your cup in the tray for your class so that they can be placed outside.

PRE-LAB QUESTIONS (THINK ABOUT IT!!!)

  1. Identify which gene is dominant and which gene is recessive for the chlorophyll trait.
  1. What are the possible genotypes (the combinations of letters) are there for this trait? For each genotype you list, identify what its phenotype would be.
  1. There are SIX possible “parental” crosses for the seeds you planted. List them below.

DATA COLLECTION

When the majority of the seeds have sprouted (approximately 10-14 days) after “planting”…

  1. Count the number of green seedlings and the number of albino seedlings (white or pale yellow).
  2. Record YOUR NUMBERS HEREGREEN:_____ALBINO:_____
  1. Contribute your data to the class data and copy the class data onto the chart below.

Lab Table / Number of GREEN seedlings / Number of ALBINO seedlings / Total (Green + Albino Seedlings)
1
2
3
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5
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9
Class Totals

CONCLUSION QUESTIONS

  1. Of the class totals that grew, what percent (%) were green? What percent (%) were albino? SHOW YOUR WORK FOR CREDIT!!!
  1. What phenotypic ratio does that give you?
  1. Judging from your data (the above calculations), WHAT WERE THE GENOTYPES OF THE ORIGINAL PARENTS? Explain why you think these are the genotypes.
  1. Using the genotype you choose in question 3, do a Punnett square and calculate the expected ratios. SHOW YOUR WORK.
  1. Compare the expected ratios to the actual ratios. Give at least two reasons why they might be different.