Study GuidePlant Biology–Genetics1. Intricacies of Inheritance1.1Intricacies of Inheritance—Made SimpleAs scientists continued breeding experiments and improved microscopes, they learned thatinheritance is more complex than Mendel first described. Mendel’s laws still matter, but many traits donot follow his simple patterns. Let’s break down theseimportant exceptionsin a clear, student-friendly way.1.2When Mendel’s Ratios Don’t Work: Gene LinkageAfter scientists acceptedMendel’s Law of Independent Assortment, they noticed something odd.Some crosses didnotproduce the expected9:3:3:1ratio in the F₂generation.What was happening?•The parental (original) traits appearedvery often•New combinations of traits appearedrarelyTo explain this, scientists usedparsimony, which means choosing thesimplest explanation that fitsthe facts.The answer waslinkage.Linkage explained•Some genes are locatedclose together on the same chromosome•Because they are close, they tend to be inheritedtogether•This breaks Mendel’s assumption that genes always assort independently1.3Linkage and Crossing OverLinkage explains why parental traits stay together—but what about thenew combinationsthatappear sometimes?Preview Mode
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