The main goal of school science is to enable learners to become scientifically literate through their participation in scientific discourses (McNeill & Krajcik, 2009). One of the key elements of scientific discourses is the ability to construct scientific explanations that consist of valid claims supported by appropriate evidence (e.g., McNeill & Krajcik, 2006, Sadler, 2004; Sandoval & Reiser, 2004). Curricula scaffolds may help students construct scientific explanations and achieve their learning goals. This dissertation study is part of a larger study designed to support fifth through seventh grade students' learning about genetic inheritance through curricula scaffolds. Seventh grade students in this study interacted with a Web Based Inquiry Science Environment (WISE) unit called "From Genotype to Phenotype" that had curricula scaffolds. Informed by the Scaffolded Knowledge Integration, two versions of the unit were developed around concepts on genetic inheritance. Version one of the units was explicit on explaining to students how to make a claim and support it with appropriate evidence. Although the science concepts covered were the same, Version two was not explicit on claims and evidence use. Embedded in the units were scaffolding supports in the form of prompts. This dissertation study explored students' responses to the scaffolding support prompts using a knowledge integration (KI) rubric as described by Linn and His (2000). Two teachers, each with about 150 students in five classes of about 25 each, participated in the study. Each teacher had three classes of students that received a version one and the other two classed received version two of "From Genotype to Phenotype" unit. Using the Statistical Package for Social Scientists (SPSS), I explored whether students' scores, as measured by the KI rubric, varied by the unit version the students received or by the teacher they had. The findings suggested that the two versions of the unit were equally valuable as there were no significant differences in test scores between students who interacted with different unit versions, F(1, 141) = 3.35, p = 0.07. However, there was a significant difference between test scores of students who had different teachers, F(1, 141) = 12.51, p = 0.001.Furthermore, apart from scoring for scientific accuracy, responses were also examined to establish whether students held some of the conceptions reported in literature about genetic inheritance. Where possible, attempts were made to identify whether students were using evidence from the unit or their out-of-school experiences in their responses to the scaffolding support prompts. It was evident that about half of the students attributed most of their inherited traits to a specific parent they resemble for that trait. In this dissertation study, the term students' resemblance theory was used to refer to the aforementioned students' reasoning. Additional, I argue that students' resemblance theory may be used to explain students' thinking when they incorrectly believe that boys or girls inherit more genes from their father or mother based on gender resemblance. Consequently, I argued that students' resemblance theory may influence students' learning and understanding about Mendel's law of segregation which include the following principles; genes exist in more than one form, offspring inherit two alleles for each trait, allele pairs separate during meiosis and alleles can be recessive or dominant. This study documented students' conceptions related to Mendel's law of segregation.
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