Identical twins have identical DNA. That makes it hard when genetic information is used in criminal cases. Last week, Czech police dogs have been shown to be able to sniff the difference in identical twins.
What are the dogs smelling? The major histocompatibility complex (MHC), an area of the genome that codes for immune system proteins, is linked to people and animal’s ability recognize each other by smell: in a well-known 1995 study, young women overwhelmingly preferred the aroma of sweaty T-shirts of men who had different MHC profiles than they. It’s possible that what the dogs are sniffing is some variation in the expression of those proteins, though this study doesn’t attempt to address a biochemical mechanism.
This is Krista and Tatiana Hogan, conjoined twins that share a neural bridge in the thalamus. This means that they can possibly share senses and thoughts. Check out the video.
Read more about them in the NY Times feature: http://www.nytimes.com/2011/05/29/magazine/could-conjoined-twins-share-a-mind.html?ref=science
