Genes related to the erbA DNA sequence that was first isolated from the avian erythroblastosis virus (ERYTHROBLASTOSIS VIRUS, AVIAN), v-erbA. In cells, erbA genes encode thyroid hormone receptors (RECEPTORS, THYROID HORMONE). Two distinct c-erbA genes have been identified: erbA-alpha located at 17q21; and erbA-beta located at 3p24. Truncations at the N- and C-terminals of erbA result in products resembling v-erbA. Truncations affect hormone responsiveness but not DNA binding capacity.