13 Jan When you record phenotypic rat

Lesson 7 Laboratory: Punnett Squares

Part I: Answer the following questions utilizing the virtual laboratory simulation:

TYPE ANSWERS HERE

1. Recessive 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

2. If a fruit fly is heterozygous for eye color (Bb) what alleles will be present in his sperm?
a. 50% will contain “B” and 50% will contain “b”
b. 100% will contain “b”
c. 25% will contain “B” and 75% will contain “b”
c. 100% will contain “B”

3. In fruit flies, black eye color is dominant over sepia. Using the letter B to represent eye color, what is the genotype of a heterozygous black eyed fly?
a. BB
b. bb
c. Bb
d. BBbb

4. All of the offspring of two black eyed flies are also 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

5. Some of the offspring of two black eyed flies have sepia eyes. 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 below.

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: