Genetics

Genetics connects the tiny scale of DNA to the traits you can see. This topic follows that path in order. You begin with DNA base pairing and replication, where A pairs with T and C pairs with G, and each new strand keeps one original half. Next is cell division: mitosis makes two identical body cells, while meiosis makes four different sex cells with half the chromosomes. Mixing up the counts is the most common error. Then you meet dominant and recessive alleles, and why a recessive trait can skip a generation and reappear. The last page is Punnett squares. The grid itself is easy; the mistakes come from writing the parents' alleles wrongly or reading the ratio off the finished square incorrectly. Work through the pages in order, because each one builds on the last. When you finish a practice question, say in plain words what the answer means for real offspring, not just the letters in the grid.