HDID-1 mice drink substantial amounts of a relatively high concentration of ethanol (20%) in limited access tests during the circadian dark. The realized heritability of the BEC developed from this behavior across 11 generations of selection is low (approximately 9%), which has undoubtedly contributed to the slow increase in BEC and ethanol intake over generations. The approximate realized heritability of h2 = .096 was lower than that estimated from inbred strains, in which it ranged from .46 to .74 (13). Differences between such estimates assessed in inbred strains and selected lines are not unexpected. They can arise from many features that distinguish the experimental populations (e.g., no heterozygotes in inbreds, many in selected lines; for discussion see ref. 17).
