After hybridization, a hybrid has 50% of its DNA from each parent since it gets one chromosome of each type from each parent. Over time, one parent's DNA may be gradually lost if it contains alleles which are not well adapted to current conditions due to natural selection. Erroneous recombination, especially unequal crossing over, can lead to the elimination of parts of a chromosome.
Work Step by Step
Review earlier chapters on crossing over, especially erroneous forms of that process, and review the concept of natural selection. F1 hybrids will theoretically have equal inheritance of genes from both parents, but after this generation selection pressure may begin to change this and the potential lingering effects of more random events (recombination, crossing over) increase the odds that the inheritance proportions will change.