Teacher: Subject/Class: 8 th Grade Science Date/Period:
Objective(s): What will students know/be able to do at the end of class?
When/how will I post, state, reinforce, and review the objective(s) during the lesson?
Are my objectives aligned with state standards and have I tagged each objective accordingly?
 SWBAT define incomplete dominance and codominance and use Punnett Squares to predict possible offspring in each type of cross.
Assessment(s): How will I measure my each student’s mastery of the objective(s)?
Are my assessments aligned with the day’s objective(s)?
Formative Assessments Link to Summative Assessments
 Exit Ticket/Homework Assignment  Weekly quiz, Unit Quiz, NY State Intermediate
Science Exam
Key Ideas: What 3-5 key ideas or steps will I emphasize?
Potential Misunderstandings: What might students misunderstand or struggle with?
 Incomplete dominance is when the two alleles are different and express a third phenotype (that is midway between the others).
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Confusion between single dominance and special types of dominance.
Not knowing when to apply which rule (reading problems)
 Co-dominance is when there are more than one dominant alleles for a trait. If both are present, then both are expressed.
Agenda
Time Mins Description of Instruction
Opening
Review: What will students do upon entering class? Is it quick & do-able?
Do Now: Pedigree/Genotype Review
7
Preview: How will I preview objective(s), agenda, and assessment?
Scholar read aim. Teacher review agenda, exit ticket to be given at end of class.
Hook: How will I capture the class’s interest/ motivate them to learn?
20
You have asked me so many times about red and white flowers making pink flowers, skin color, eye color and hair color in humans, and other special cases in genetics. Today, we’re going to explore a couple of different types of dominance and use Punnett Squares to predict what types of offspring could be produced from these crosses.
Intro to New Material (“I/We”)
Description
On powerpoint: put pictures of white, red and pink flowers. Ask scholars to take 2 minutes and write what they think is different about how these flowers inherited their color.
Next, put up pictures of white cat, black cat, and spotted or striped cat. Ask scholars to take 2 minutes to write what they think is different about how these organisms inherited their fur color.
(Looking for the red and white mixing to get pink, and both showing up to get stripes)
You already know how to create a Punnett Square to predict the traits of offspring from a given set of parents. I want you to complete a Punnett
Square using the rules you’ve used before and tell me what you think it means.
Materials
Do Now (part of packet)
Packet, powerpoint

15
3
(Give P-square with R = red and W = white)
(After they have attempted…demonstrate the correct way to complete the
P-square and review genotypes and phenotypes.)
This is an example of incomplete dominance. With incomplete dominance, a cross between organisms with two different phenotypes produces offspring with a third phenotype that is a blending of the parental traits.
Write that definition down.
Now, let’s look at those cats. We’re going to use a Punnett Square again to predict the offspring from this cross. What do you think it will be?
(Give P-square with B= black and W = white)
(After they have attempted…demonstrate the correct way to complete the
P-square and review genotypes and phenotypes.)
This was an example of codominance- BOTH of the phenotypes are shown when the organism has both alleles.
Now, I want you to take a look at blood type. Can anyone name the different types of blood that humans can have? (A, B, AB, O)
Differentiation
Teacher circulating to help struggling scholars.
Independent Practice (“You”)
Description
Blood type is an example of codominance. Take a look at the following question and see if you can use the table to answer the questions. Then, take a look at the questions and see if you can use P-squares to determine the correct answers.
Scholars work in pairs to complete Blood type questions.
Differentiation
The teacher is circulating to assist scholars that are having difficulties.
Closing: How will I revisit objective(s) & ensure understanding?
Description
Class turns to exit ticket page in packet- completes two P-Squares (co and incomplete dominance.
HW- Codominance and Incomplete dominance Sample Problems
Packet
Packet

_____________________________________________ ________________________________________
Aim: SWBAT define incomplete dominance and codominance and use Punnett Squares to predict possible offspring in each type of cross.
Do Now:
Look at the pedigree below and determine the genotypes and phenotypes of each individual.
Hmmm… What happened to those flowers?
Key:
E = elephants with tusks e = elephants without tusks
Shaded symbols have no tusks
Write below what you think happened to make the pink flower:
_______________________________________________________________________________________
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Mixed cats???
Write below what you think caused the cat to have both colors:
_______________________________________________________________________________________
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Now, try your hand at the Punnett Square:

The name for this type of dominance is incomplete dominance.
Incomplete dominance is when
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The other type of dominance is called codominance.
Codominance is when
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Independent Practice: Blood Type
Human blood is classified into four blood types: A, B, AB, and O. An offspring’s blood type is determined by genes passed on from the offspring’s parents. Each parent gives an offspring one gene for blood type. The combination of the two genes determines the offspring’s blood type.
There are three genes, A , B , and o , that are responsible for the four blood types. The table below shows how these three genes interact to produce the four blood types.

The Punnett square below shows the probability of blood types in the offspring of two parents. One parent’s blood type genes are AB and the other parent’s blood type genes are
Ao .
Based on this Punnett square, identify the expected percentage of offspring in each of the four blood types.
Blood type A: ___________________ % Blood type B: ___________________ %
Blood type O: ___________________ % Blood type AB: ___________________ %
Complete the Punnett square below, which shows a cross between two parents whose genes for blood type are
AB .
Blood Type Challenge:
A father has type O blood and a mother has type AB blood.
What blood types can their children have?

Suppose two newborn babies were accidentally mixed up in the hospital. In an effort to determine the parents of each baby, the blood types of the babies and the parents were determined.
Baby 1/type O
Baby 2/type A
Mrs. Brown/type B
Mr. Brown/type AB
Mrs. Smith/type B
Mr. Smith/type B
Baby 1 belongs to which parents?
Draw two Punnett Squares to prove your answer:

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Exit Ticket: Codominance and Incomplete Dominance
1.
A cross between a blue bird & a white bird produces offspring that are silver. The color of these birds is determined by just two alleles. a) What are the genotypes of the parent birds in the original cross? b) What is/are the genotype(s) of the silver offspring? c) What would be the possibility of having each type of bird?
2.
A very common phenotype used in questions about codominance is roan fur in cattle. Cattle can be red (RR = all red hairs), white (WW = all white hairs), or roan (RW = red & white hairs together)- a good example of codominance. Predict the phenotypic ratios of offspring when a homozygous white cow is crossed with a roan bull.

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Homework: Incomplete Dominance and Codominance Practice
1.
The color of fruit for plant "X" is determined by two alleles. When two plants with orange fruits are crossed the following ratios are present in the offspring: 25% red fruit, 50% orange fruit, 25% yellow fruit. What are the genotypes of the parent orange-fruited plants?
2.
A cross between a black cat & a tan cat produces a tabby pattern (black & tan fur together). a) What pattern of inheritence does this illustrate? b) What percent of kittens would have tan fur if a tabby cat is crossed with a black cat?