Solution: Pure line is a breed or strain of plants and animals that have homozygous alleles and have similar characters for various generations. In-breeding is used to establish pure lineages. Inbreeding occurs when closely related individuals are bred together. For this aim, a superior male and superior female are chosen and mated. Superior males and females are chosen from the next generation to continue the process. To achieve a pure line, this process is repeated for 4 to 5 generations. Inbreeding increases homozygosity, allowing for the production of pure lineages. This approach, however, has a serious flaw: inbreeding depression.