SIRS Discoverer, SIRS Issues Researcher, and Gale's Research in Context are three databases that are excellent starting points. Try using search terms like:
In SIRS Discoverer: genes; genetic engineering; human genetics; genetic modification; genetically modified food(s); birth defects, genetic aspects; human genetics, moral and ethical aspects
In SIRS Issues Researcher: genetic testing; genetically altered foods; genetic manipulation; genetically engineered foods; genetic engineering, risk assessment/government and policy/law and legislation; genomes; genetic engineering industry; genetic screening; genetics, research
In Gale Research in Context: desired traits; genetically modified organism; selective breeding; breeding for productivity; breeding for purpose; breeding for welfare; artificial selection; gene therapy
Content is written explicitly for middle school students on a variety of topics, including government, U.S. and world history, geography, literature, science, and social issues.
SIRS Issues Researcher is an editorially curated pro/con database designed for middle and high school students, university undergraduates, instructors, and librarians.