A Birds' Eye View on the Evolution and Inheritance of Germline/Soma Genome Differences

Passerine birds make up two thirds of all bird species and all likely exhibit extensive germline/soma genome differences through a germline-restricted chromosome (GRC). This peculiar chromosome is present in one copy in male germline cells, in two copies in female germline cells, and absent from somatic cells as well as male gametes. Recent advances in cytogenetics and multi-omics have finally made studying the evolution of GRC genes and their expression during germline development possible, and also revealed occasional paternal inheritance of the GRC. Here, I will highlight unpublished results towards answering the when, how, and why of GRC evolution.