Virtual Lab: Punnett Squares

Worksheet

Part I: Answer the following questions:

1. Which of the following is most inclusive?

a. allele

b. genotype

2. Dominant alleles are represented by:

a. an upper case letter

b. a lower case letter

c. it does not matter what type of letter is used

3. In fruit flies, gray body color is dominant over black body color. Using the letter G to represent body color, what is the genotype of a heterozygous gray bodied fly?

a. GG

b. gg

c. Gg

d. GGgg

4. All of the offspring of two gray bodied flys are also gray. What can you conclude about the genotypes of the parent flies?

a. They are both heterozygous

b. They are both homozygous dominant

c. They are both homozygous recessive

d. You cannot conclude anything definitively about the parental genotypes

5. Some of the offspring of two gray bodied flies are black. What can you conclude about the genotypes of the parent flies?

a. They are both heterozygous

b. They are both homozygous dominant

c. They are both homozygous recessive

d. You cannot conclude anything definitively about the parental genotypes

Part II: Follow the instructions in the Question column to complete the virtual lab scenarios and record your data:

Complete all ten scenarios and record your results in Table 1.

When you record a ratio, whether it is genotypic or phenotypic ratio, always record the most dominant characteristic first, followed by the recessive. For example, when recording genotypic ratios:

1) If your offspring genotypes include 1 GG, 2 Gg, and 1 gg, the ratio would be: 1 GG : 2 Gg : 1 gg

2) If your offspring genotypes include 2 GG and 2 Gg, the ratio would be: 2 GG : 2 gg (or 1:1 in the reduced form)

3) If your offspring genotypes are 4 gg, then the ratio would be written as:: 4 gg

When you record phenotypic ratios for a monohybrid cross, there are only two possible phenotypes - either the dominant phenotype or the recessive phenotype. So you do not need to indicate the phenotype, simply put the dominant # first, followed by the recessive #:

4) If your offspring phenotypes are 3 dominant and 1 recessive, the ratio is: 3:1

5) If your offspring phenotypes are 4 dominant and 0 recessive, the ratio is: 4:0

6) If your offspring phenotypes are 0 dominant and 4 recessive, the ratio is: 0:4

Table 1:

Scenario # Genotype of

Parent I Genotype of

Parent II Genotypic Ratio of Offspring Phenotypic Ratio of Offspring
1
2
3
4
5
6
7
8
9
10