Here’s why you’re going to get it wrong on the exam: Teaching by Focusing on Misconceptions Morris Maduro, Univ of California, Riverside

The Gist Intro Biology, st - or 2 nd -year students Chapters 1-16 of Campbell I give students summary notes, learning outcomes, past exams, how-to guide [see Poster and BLC Wiki site] In class, I cover topics and go straight to the misconceptions (which aren’t in the notes)

Example: “Independent Assortment” First part: Monohybrid crosses & Mendel’s Law of Segregation

A dihybrid cross Phenotype ratios: 9 : 3 : 3 : 1

Most of you think that “Independent Assortment” means “the genes affect different characters.” This is wrong.

A dihybrid cross Phenotype ratios: 9 : 3 : 3 : 1

All textbooks depict the 9:3:3:1 ratio using genes exerting ‘parallel’ effects on phenotype. Students misunderstand use of ‘independent’. Why the misconception? Linked genes (which fail to assort independently) are also shown as ‘parallel’ pairs, e.g. b and vg in flies. Unlinked genes can act in the same process (e.g. two eye color genes in flies) but still assort independently. The misconception is falsifiable:

Sample assessment: In Mendel’s Law of Independent Assortment, the word “assortment” refers to: (A)The functions of the genes. (B)Whether genes are on the same chromosome. (C)Whether single genes show a 1:1 segregation. (D) Distribution of alleles into gametes. (E)Whether a cross gives a 9:3:3:1 ratio.

What does this achieve? Forces students to re-evaluate what they think they learned previously Holds their attention more than just explaining the figures They will bring their questions to office hours Rewards students who attended class

Thank you. Downloads: BLC Wiki site under Maduro poster abstract (A-11) (sample exams, lecture notes, concepts quiz, FAQ file, etc.)

Sample assessment 2: A dihybrid AaBb plant is producing gametes. If the two genes assort independently, the four gamete types are ____ in proportion ____: (A) A, a, B and b; 1:1:1:1 (B) A, a, B and b; 9:3:3:1 (C) AB, Ab, aB and ab; 1:1:1:1 (D) AB, Ab, aB and ab; 9:3:3:1 (E) AB and ab ; 3:1

Sample assessment 3: Two genes s and t are found on two different chromosomes. The two genes must: (A)Show less than 50% recombination. (B)Assort independently. (C)Affect different aspects of phenotype, like color vs. shape. (D) Show greater than 50% recombination. (E)Both (B) and (C) are correct.

Law of Independent Assortment meiocyte in F 1, genotype YyRr OR TWO POSSIBLE ALIGNMENTS AT METAPHASE I gametes yR and Yrgametes yr and YR y y y y y