Heredity & the Environment Tobacco Albino Seeds

I. Background Information: An organism’s phenotype or physical appearance for a particular trait is the result of both its genetic makeup and the environment. Genes may be turned off by environmental factors: light, temperature, etc. Why use a gene/protein when you don’t need it? The energy efficiency provided is a survival adaptation

I. Background Information: Tobacco seeds will germinate and grow in as little as three days if they are kept moist. The seeds contain an embryonic plant along with cotyledons that serve as a food source for the embryonic plant before its leaves develop, produce chlorophyll, and carry out photosynthesis. Tobacco seedlings that possess a dominant allele for chlorophyll production will produce chlorophyll if environmental conditions are favorable. However, tobacco seedlings that possess two recessive alleles are genetically programmed to be albino, and will not possess chlorophyll. Therefore, photosynthesis cannot occur in albino plants.

II. Research Question: Will the presence of sunlight effect the expression of the genes for chlorophyll production in tobacco seedlings?

III. Developing your Hypotheses What is the independent variable you are manipulating/testing? Presence of light B. Expression of genes What is the dependent variable that you will measure the effects of manipulating the independent variable (results)? What is the expected ratio when the seeds are grown in the light in both parents are heterozygous? Perform a Punnett Square.

IV. Model

V. Experimental Design Research Question: Null Hypothesis: Alternative Hypothesis 1 (light): Alternative Hypothesis 2 (chosen variable): Independent Variable: Experimental Group(s): Control Group: Dependent Variable: Constants:

VI. Materials & Procedures Water, tap Marker 3 Disposable plastic petri dishes (100 x 15 mm) Pipet Paper towel Tobacco seeds 30/experimental group Lightproof storage area or covers (from parents heterozygous for albinism) Different colored lights, salt solution, OR vinegar solution

Procedure: With a piece of tape: label the bottom of one Petri dish “light”; the bottom of another Petri dish “dark. Label all with your group name and date. Place a piece of moistened filter paper into the bottom half of each Petri dish. Sprinkle 30 tobacco seeds evenly over the moistened paper in each Petri dish. Use a toothpick to spread out in the two dishes. Replace the cover on each Petri dish. Place the dish labeled “light” in a well- lighted area under the grow lights. Place the dish labeled “dark” in a completely darkened area where it will receive absolutely no light. (place your Petri dish in the designated drawer for your class). Place your third petri dish in the area or environmental condition that your group has selected. Allow the seeds to germinate for one week. Let the dishes sit undisturbed except to add water if the filter paper should become dry. If the dish in the dark needs added water, add it quickly and in a reduced light environment. (this is your groups responsibility – if your seeds dry out you will receive 0 for the results) Observe the 3 Petri dishes at the end of one week. Some seedlings will be pale in color (albino) with little or no green pigment. Other seedlings will have green areas forming. When nearly all the seedlings have germinated, count each seedling as either green or albino. Record your results in the data table below: