This article I found at www.sciencedaily.com reports on a study published yesterday in Nature Genetics in which researchers managed to recreate hemoglobin cells of the extinct Siberian mammoth. The DNA was taken from the bones of a mammoth that was approximately 25,000 to 43,000 years old. The process of recreating the hemoglobin is described succinctly in the article:
"The team converted the mammoth hemoglobin DNA sequences into RNA, and inserted them into modern-day E. coli bacteria, which then manufactured the authentic mammoth protein."
According to one of the professors involved in the study, the resulting hemoglobin is identical to what would be found in the actual mammoth when it was living.
One of the most interesting discoveries to come from this study was the mammoth's adaptation to arctic conditions. Apparently, this animal had the ability to lower the temperature in its four legs so as to reduce heat lost to snow and ice.
Here's the full article: http://www.sciencedaily.com/releases/2010/05/100503111826.htm