Abstract
The purpose of this study was to develop and validate a two-tier diagnostic instrument — Two-Tier Diagnostic Test for Genetics (TTDTG) to find seventh graders’ alternative conceptions of genetics. 1606 students were sampled randomly from six junior high schools in Taoyuan County and diagnosed using the TTDTG. Results showed that the average difficulty and average index of discrimination of the TTDTG were 0.45 and 0.48 respectively. The Cronbach alpha value for internal consistency was 0.73. Even though they had received instruction in biology classrooms, seventh-grade students still had alternative conceptions about the results of mitosis, the process and results of meiosis, genes and traits, dominance and recessiveness, the definition and recognition of homologous chromosomes, the definition and formation of diploid chromosomes, acquired inherence, existence of sex chromosomes, relationships among genes, chromosomes, and DNA, and Mendel’s laws of inheritance. Findings of this study suggested that the TTDTG could be used as diagnostic test for genetics and the identification of alternative genetic conceptions can be valuable resources for diagnosis, instruction and curriculum development of genetics.
| Keywords: | two-tier diagnostic test; junior high school; genetics; alternative conceptions |
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