Download Desiree`s Baby Source: Unrau, N. (2008). Content Area Re

Marion Slater
SEC-371
Activity Set
Elizabeth Daigle
Writing Strategy: Desiree’s Baby
Source: Unrau, N. (2008). Content Area Reading and Writing. New Jersey: Pearson
Philosophy: “Summary writing focuses on ideas at a deeper level than mental
review…Analytical writing engages students in reformulating and extending the text.” (Unrau,
pg. 218).
Rationale: Students will apply a genetic technique to determine genotypes and calculate
frequencies of phenotypes.
Objectives: Students will learn that some characteristics cannot be explained by a simple
Mendelian cross.
Procedure:
1. Introduce topic: Discuss what student’s thought of the story of Desiree’s Baby. Is
this scientifically accurate?
2. Watch YouTube clip:
http://www.youtube.com/watch?v=3uvUZbUwOiA&feature=player_embedded
Black parents who have a white baby.
Now that we know this is scientifically possible, what could explain this?
3. Students get into pairs to solve the Punnett square and calculate the frequencies.
4. Discuss their findings and the questions as a class. Teacher: draws the Punnett
square on the board guided by the students. Teacher: draws the table on the board with
student guidance.
5. Introduce new genetic terms: Incomplete Dominance, Codominance.
6. Questions? Conclusions?
Resources: 1. Adapted from: RACE-The Power of an Illusion:
http://www.pbs.org/race/000_About/002_04-teachers-06b.htm
Name: ______________
Date/Period: __________
Skin Color is a polygenic trait
Differences in skin color are due to differences in the amount of melanin, a color pigment,
produced by each skin cell. Three genes control the synthesis of melanin. Each gene has two
forms: an allele for high melanin production (dark) skin (A,B,C) and an allele for low melanin
production (light) skin (a,b,c). Each dark skin allele in the genotype adds a small but equal
amount of pigment to the skin. There are seven different shades of skin color ranging from
very dark (AABBCC) to very light (aabbcc). Most individuals produce a medium amount of
melanin and are of intermediate skin color (AaBbCc).
Complete the following Punnett square to show the possible cross between two individuals of
intermediate skin color:
AaBbCc X AaBbCc
Gametes: ABC
ABC
ABc
AbC
Abc
aBC
aBc
abC
abc
ABc
AbC
Abc
aBC
aBc
abC
abc
Rank the squares 0-6, counting how many dominant alleles are in the genotype. Include this in
each box to refer back to later. As an example, genotype: aaBbcc only has 1 dominant allele so
it would be designated with a 1.
Questions: Answer each of the questions (3-6) in paragraph form.
1. Each parent produces different types of gametes which can combine in 65 different ways.
Complete the following table:
# of dark skin alleles in the genotype
Phenotype: Skin Color
Phenotype ratio: # of offspring/64
0
1
2
3
4
5
6
2. How many of these 64 possible offspring have skin that is darker than their parents?
3. Are darker skin alleles dominant to the lighter skin alleles?
4. There are more than 7 shades of skin color. Can you offer another explanation?
5. Use this model of skin color inheritance and the information provided in Desiree’s Baby to
develop a new genotype for Armand’s parents and Armand; Desiree’s parents and Desiree; and
their baby.
6. In your own opinion, should race really matter? Is race as simple as the science that we
learned? Or is there more to it?