DESIGNING A STEM LESSON USING PROJECT-BASED TEACHING AND LEARNING APPROACH

Teacher: RENZ ANGELO D. CALZADA Region: XI

School: MABINI NATIONAL HIGH SCHOOL Division: Davao City Division

DESIGNING A STEM LESSON USING A PROJECT-BASED LEARNING APPROACH

PEDIGREE ANALYSIS

(General Biology 2)

Content Standards: The learners understand Mendel’s Laws of Inheritance.

Performance Standard: The learners shall be able to make a Pedigree Analysis in the learner’s family using a simple genetic trait.

Learning Competencies: The learners shall be able to construct pedigrees and predict genotypes based on pedigree analysis (STEM_BIO11/12-IIIa-b-1)

LEARNING TARGET: At the end of the lesson, the learners will be able to:

• identify the mode of inheritance of a particular trait given the pedigree;

• predict the genotypes of parents; and

• compute the probability of occurrence of an affected offspring in a given cross.

Essential Question: Big Bang Theory states that planets are born from what remains of a dead star. Given this theory planets were surely once unable to sustain life. How do you think did planet Earth change from being unlivable to the Earth we know now holding not just one but thousands (even millions) of different kinds of living organisms?

The students will be asked to group themselves and follow the steps below.

1. Divide learners into groups of four.

2. Provide copies of four sample pedigrees. (See samples in Figure 1 at the end of this document.)

3. For each pedigree, provide questions for the group to answer

I. Identify the mode of inheritance

II. Write down the genotypes of specific individuals

III. Compute for the probability of having an affected offspring

FIGURE 1

A. Look at the family of IV-9 and IV-10. If the trait is dominant, is it possible for them to have an affected offspring? (Answer: NO. If the trait is dominant, then unaffected individuals are homozygous recessive. Two recessive individuals CANNOT produce a dominant offspring.)

B. If the trait is recessive, is it also possible for IV-9 and IV-10 to have an unaffected offspring? (Answer: YES. This can happen if both parents are heterozygous for the trait, which means they can each give a recessive allele to produce a homozygous recessive offspring.)

C. Based on your answers for a) and b), is the trait dominant or recessive? (Answer: RECESSIVE)

D. Give the genotypes of the following: i. IV-9 (Answer: Dd) ii. IV-10 (Answer: Dd) iii. V-1 (Answer: DD or Dd) iv. I-1 (Answer: dd) v. I-2 (Answer: Dd)

E. If IV-9 and IV-10 were to have another child, what is the probability that they will have an affected offspring? (Answer: 1/4 or 25% following the Mendelian ratio from a hybrid cross)

FIGURE 2

A. Is this trait dominant or recessive? (Answer: RECESSIVE. If the trait were dominant, then individuals I-3 and I-4 are both homozygous recessive, which means they CANNOT have a dominant offspring.)

B. What are the most probable genotypes of I-3 and I-4? (Answer: Dd and Dd in order for each parent to be able to contribute a recessive allele to give rise to a recessive offspring.)

C. What are the most probable genotypes of II-4 and II-5? (Answer: Dd and Dd. Same reason as b.)

D. What is the probability that II-4 and II-5 will have another normal offspring? (Answer: 75%. A hybrid cross will produce 75% dominant offspring and 25% recessive offspring.)

ENRICHMENT

1. As a homework, assign each learner to construct a pedigree of an authentic family using any of the following traits:

I. With (dominant) or without finger hair (recessive)

II. Normal (dominant) or hitchhiker’s thumb (recessive)

III. Widow’s peak (dominant) or straight hairline (recessive)

IV. Free (dominant) or attached earlobe (recessive)

V. Curly (dominant), wavy (heterozygous) or straight (recessive) hair

2. B. Where possible, determine the genotypes of every individual in the family