The festivity of imbuing discarded DNA

A friend of mine is studying in Chiang Mai, Thailand, and she recently participated in Loi Kratong, an all-out lantern lighting festival that falls on the full moon of the 12th lunar month (usually November) in which one places some money, a strand of one's hair and a fingernail clipping on a handmade raft (i.e. kratong) to expiate bad luck and incur some good. The kratong is then set afloat in the river with thousands of others, while paper lanterns and fireworks take over the sky.

That got me thinking about rituals, ceremonies, and superstitions involving the application or appropriation of one's DNA...For instance:

• Superstitions in many Eastern cultures warn against clipping one's nails at night
• Many spells (of a contested variety) are purportedly enhanced by affixing the hair or fingernail clippings of the spell's subject into the candle; voodoo dolls are similarly manufactured.
• On the Cook Islands, firstborn sons undergo a "hair cutting ceremony" in which up to 400 friends and relatives attend, each receiving a strand of the boy's hair; the ceremony is a demonstration that the son is not afraid of giving his mana/power over to others, as perpetually long-haired ancestors believed
• During a Danpatsu Ceremony, a retiring rikishi (i.e. sumo wrestler) will have strands of his chonmage cut by paying fans (chonmages were originally worn for pure function: to keep the samurai helmet in place; finally, a Sumo elder called an okakata will snip the remaining topknot.

And of course there are those who'll analyze your fingernails or hair (or, my favorite, your irises!) for nutritional deficiencies