Step 2: Hypothesize

Fruit flies can have many body colors that are different from the normal (or "wildtype") yellow-brown color of most flies. One of those colors is ebony, which is a slightly darker color than the wildtype. Scientists are not 100% sure how this trait is inherited, although several experiments have suggested that it is recessive.
Wildtype Ebony

In order to test the inheritance of the ebony trait for ourselves, we will be crossing wildtype females with ebony males. In order to best come up with your hypothesis, answer the questions below. Please note that although here a letter has been used to represent the wildtype genotype, in the research community wildtype flies are represented by "+" symbols.

What Results Should You Expect?

1. Recessive traits are represented by which type of letters?
Capital.
Lowercase.
Vowels.
Consonants.

2. According to the work of other scientists, the ebony trait is recessive. Therefore, what should we predict the genotype of an ebony fly to be?
Ee.
EE.
ee.
eE.

3. If the wildtype fly we use in our cross is homozygous, what is its genotype?
Ee.
EE.
ee.
eE.

4. On a separate sheet of paper, show the cross of the wildtype female to the ebony male using a Punnett square (shown below). What percentage of the offspring in the F1 (first generation) will be ebony?
50%.
75%.
100%.
0%.

5. According to your Punnett square, what percentage will be wildtype?
50%.
75%.
100%.
0%.

6. All the offspring that are wildtype will have what genotype?
Ee.
EE.
ee.
GG.

7. On your Punnett square, you wrote letters above each space. What does each single letter represent?
A complete genotype.
A gamete that contains one allele of the gene from the parent.
A gamete that contains a gene from the parent.
A body cell that contains a gene from the parent.

8. A heterozygous fly (Ee) has the same phenotype as a homozygous dominant fly (EE). Why is this so?
Since the E allele causes the fly to have at least half its proteins for body color be normal, this is enough for the fly to have a normal body color.
This is false; since a heterozygous fly has only half the proteins for normal body color it will be ebony (and therefore have a different phenotype from the EE fly).
The big E is capital and therefore stronger than the little e, so the heterozygous fly will be wildtype just like the homozygous dominant fly.