Liaison analysis between school grades in genetics contents of biology textbooks under Korean secondary school was performed. Analyzing the liaisons between Inquiry Topics, Inquiry Patterns, Inquiry Process, and Inquiry Situations, we took grades between the 9th and the 12th except 10th: the number of the Inquiry Topics in average were 12, 10, 22 in 9th, 11th, and 12th grades` textbooks each, and their contents for `repetition`, `variation`, `development`, and `skipping`, were 18, 24, 29, and 29% each for between the 9th and 11th grade, and 17, 13, 35, 35% for between 11th to 12th grades, indicating that development and disparities were increased exclusively compared to repeat and variation as grade rises. `Inquiry process` composed of performances and materials interpretations mainly, but it requires to change improving self-trial learning and extending the balanced inquiry efficiency. Observing the part of Inquiry Situation, there was the most of `Pure Science`, nevertheless `Social-Technical` Research Situation should take more portion to help STS thinking. `Readings` was established into 18, 45, 30% of `repetition`, `change`, and `development` on the transfer of 9th to 11th grade: having the most of `change` that suggests contents in a different way. However, `development` and `skipping` were increased to 48 and 19% with intensified contents in transferring 11th to 12th grade. Contents of advanced biology-related genetics increased on the 11th and 12th grades, significantly intensifying the capacity and level of biology compared to the 9th grades which mainly is composed with classical Mendel`s genetics.