Sex chromosomes represent a unique part of the genome in many eukaryotic organisms. They differ significantly from autosomes by their evolution, specific features, and meiotic behaviour. Recent advances in the knowledge of sex chromosomes in non-model organisms have been largely enabled by modern cytogenetic methods. The present study explores several topics related to sex chromosomes in Lepidoptera, the largest group of animals with female heterogamety, using methods of molecular cytogenetics, immunocytogenetics, and molecular biology. These topics include physical mapping of chromosomes by BAC-FISH, molecular differentiation and composition of the W chromosome, differences in the evolution of the W and Z chromosome, and meiotic sex chromosome inactivation. The results obtained brought new information not only about the W and Z chromosomes in Lepidoptera, but also about the evolution and specific features of sex chromosomes in general.

Plant breeding and the development of new or better varieties of plants are essential parts of modern agronomy, horticulture and forestry. The basis for such improvement is a knowledge of the factors and principles of genetics. A number of genetic studies have been made with barley in recent years. This is partly because of the many distinct heritable characters of barley plants. The cultivated species of barley offers the plant breeder and geneticist a wealth of material for genetic studies. Varieties differ in a great many readily distinguishable characters, species hybridize readily, and their small number of chromosomes make it good material for inheritance studies. The barley genetic work has been divided among the principal workers in the U.S., each being responsible for one linkage group. This station has been assigned group IV of which this study is a part. A study of the inheritance of other genes not located in linkage group IV, but appearing in the crosses used, has also been made. This investigation is a by-product of the cereal breeding and improvement program being carried on the Utah Agricultural Experiment Station.