Miss Wilcox

Biology I

Genetics – June 25, 2007

Approximate time: 50 minutes

Objectives: TSW

1.Explain incomplete dominance and codominance.

2.Apply genetic principles to solve inheritance problems including multiple alleles, incomplete dominance, and codominance. 5e

Materials:

Whiteboard, markers, overhead, construction paper, pencils, worksheet

Warm-up: Show all work.

1. Two heterozygous tall pea plants are crossed. They produce 16 seeds. How many of those seeds will likely result in short plants? Answer: 4.

Set: (review, objectives, involve, relevance)

Say, “The warm-up problem we just solved is a good example of how we use Punnett squares for solving problems of monohybrid crosses, such as those we did on Friday. Does anyone know what type of blood he or she has? (Ask students). So far, like Mendel, we have studied cases in which there was one dominant and one recessive allele. Blood type is an example of a trait for which there are multiple alleles, more than two alleles for a trait. Today, we are going to explain exceptions to Mendel's rules: incomplete dominance and codominance and situations in which there are multiple alleles.” 

Procedures:

1.Say to students, “Using your textbook, please define incomplete dominance, codominance, and multiple alleles in your notebook (3 min).”

2.Discuss definitions and provide examples. (White, red, pink snapdragons; black, white, speckled chickens; blood types A, B, AB, and O).

3.Have students make a postar with a ficticious animal or plant illustrating incomplete or codominance. Show example and what it must include.

4.Have students present.

5.Allow students to work on home worksheet, time permitting.

Closure: (restate, review, involve, preview)

Say, “Today, we explained and applied genetic principles to solve inheritance problems involving incomplete dominance and codominance. What is incomplete dominance? What is codominance? How are they difference from eachother? How are they different from complete dominance? Tomorrow, we will learn about and apply genetic principles to solve inheritance problems involving sex-linked genes.”

Assessment:

    Informal: TTW observe the student presentations on their postars on incomplete dominance or     codominance, checking for understanding of the concepts.

    Formal: TTW grade warm-up on monohybrid cross and the postar on incomplete dominance or     codominance completed by each student. The grades will          be recorded in the gradebook.