1 00:00:01,920 --> 00:00:06,440 Speaker 1: Welcome to brain Stuff production of I Heart Radio. Hey 2 00:00:06,480 --> 00:00:10,800 Speaker 1: brain Stuff Lauren Vogelbaum here with a classic brain Stuff episode. Today, 3 00:00:11,000 --> 00:00:13,720 Speaker 1: we're looking at a number of conditions in which different 4 00:00:13,720 --> 00:00:16,759 Speaker 1: cells in a person's body might be operating using a 5 00:00:16,800 --> 00:00:20,520 Speaker 1: different person's DNA, including one in which you can be 6 00:00:20,720 --> 00:00:25,840 Speaker 1: your own twin. Hey brain Stuff, Lauren vogel bam Here. 7 00:00:26,239 --> 00:00:29,520 Speaker 1: Gwen Taylor Mall, a California based singer, asked a doctor 8 00:00:29,560 --> 00:00:32,560 Speaker 1: to investigate the birthmark that stretched across the whole left 9 00:00:32,600 --> 00:00:35,600 Speaker 1: side of her torso. She wondered what role the ruddy 10 00:00:35,640 --> 00:00:38,800 Speaker 1: patch might play, if any, in a series of seemingly 11 00:00:38,880 --> 00:00:41,880 Speaker 1: disparate health conditions she had experienced for most of her life. 12 00:00:42,440 --> 00:00:45,160 Speaker 1: Mole says, everything on the left side of my body 13 00:00:45,240 --> 00:00:47,720 Speaker 1: is slightly larger than the right side. I have a 14 00:00:47,720 --> 00:00:49,960 Speaker 1: double tooth in the left side of my mouth, and 15 00:00:50,080 --> 00:00:54,240 Speaker 1: many sensitivities and allergies to foods, medications, supplements, jewelry, and 16 00:00:54,360 --> 00:00:57,920 Speaker 1: insect bites. While Mole says she hoped for answers, she 17 00:00:58,080 --> 00:01:00,600 Speaker 1: was shocked by what the doctor told her. Her birthmark 18 00:01:00,760 --> 00:01:03,760 Speaker 1: wasn't a birthmark at all. She actually carried the genetic 19 00:01:03,800 --> 00:01:06,920 Speaker 1: code of her twin a sister Mall had absorbed while 20 00:01:07,000 --> 00:01:11,120 Speaker 1: still in the womb. Mal is a chimera, someone who 21 00:01:11,160 --> 00:01:14,360 Speaker 1: carries two distinct sets of DNA, each with the genetic 22 00:01:14,400 --> 00:01:17,520 Speaker 1: code to make a completely separate person. The difference in 23 00:01:17,600 --> 00:01:21,640 Speaker 1: skin pigmentation on Mall's abdomen, these sized discrepancies between her 24 00:01:21,720 --> 00:01:24,679 Speaker 1: left and right sides, and a host of autoimmune symptoms 25 00:01:24,840 --> 00:01:29,160 Speaker 1: are caused by two warring sets of DNA. In Greek mythology, 26 00:01:29,319 --> 00:01:32,880 Speaker 1: a chimera is a fire breathing female monster that's part lion, 27 00:01:33,160 --> 00:01:36,880 Speaker 1: part goat, and part dragon. As remarkable as this creature sounds, 28 00:01:37,080 --> 00:01:40,720 Speaker 1: real life chimeras are perhaps even more astounding and probably 29 00:01:40,760 --> 00:01:45,200 Speaker 1: more common than we realize. Mall's condition, tetracomedic chimerism is 30 00:01:45,240 --> 00:01:48,440 Speaker 1: the most rare of all types of chimerism. It occurs 31 00:01:48,440 --> 00:01:51,280 Speaker 1: when two separate eggs or ova, are each fertilized by 32 00:01:51,320 --> 00:01:55,360 Speaker 1: a separate sperm. Then the fertilized eggs, called zygoats, fused 33 00:01:55,360 --> 00:01:59,000 Speaker 1: together to create a single organism with two genetically distinct 34 00:01:59,080 --> 00:02:02,280 Speaker 1: types of DNA. As the embryo cells multiply and grow, 35 00:02:02,600 --> 00:02:05,480 Speaker 1: so do the two different types of genetic material. The 36 00:02:05,520 --> 00:02:08,959 Speaker 1: result is a baby who is born a chimera. Often, 37 00:02:09,080 --> 00:02:12,279 Speaker 1: baby is born with chimerism have patchy skin or eye pigmentation, 38 00:02:12,600 --> 00:02:16,480 Speaker 1: and sometimes they carry two distinct types of red blood cells. Occasionally, 39 00:02:16,639 --> 00:02:20,320 Speaker 1: chimeras are born with ambiguous genitalia or possessing attributes of 40 00:02:20,360 --> 00:02:23,600 Speaker 1: both male and female sex organs. These symptoms can occur 41 00:02:23,720 --> 00:02:26,000 Speaker 1: not only in humans, but in other types of mammals, 42 00:02:26,040 --> 00:02:30,239 Speaker 1: including mice. Chimerism was once believed to be extremely rare, 43 00:02:30,520 --> 00:02:34,160 Speaker 1: but such conditions are commoner than we realized, as Linda Randolph, 44 00:02:34,200 --> 00:02:37,720 Speaker 1: m d. Told The New York Times. Randolph is a 45 00:02:37,760 --> 00:02:40,960 Speaker 1: pediatrician at Children's Hospital in Los Angeles, an author of 46 00:02:40,960 --> 00:02:44,360 Speaker 1: a chimerism review published in the American Journal of Medical Genetics. 47 00:02:45,200 --> 00:02:48,720 Speaker 1: In addition to genetic chimerism, the condition is commonly caused 48 00:02:48,720 --> 00:02:51,320 Speaker 1: when another genetic code is introduced to the body by 49 00:02:51,480 --> 00:02:54,760 Speaker 1: organ or tissue transplants, as well as by blood transfusions. 50 00:02:55,120 --> 00:02:58,320 Speaker 1: For example, when someone undergoes a bone marrow transplant, they'll 51 00:02:58,360 --> 00:03:00,679 Speaker 1: carry blood cells that are identical to their donor for 52 00:03:00,720 --> 00:03:02,880 Speaker 1: the rest of their lives, in addition to their own 53 00:03:02,919 --> 00:03:07,399 Speaker 1: genetically distinct blood cells. A blood transfusion, however, only produces 54 00:03:07,440 --> 00:03:10,800 Speaker 1: a temporary chimera. Condition, The donor blood cells will live 55 00:03:10,800 --> 00:03:13,040 Speaker 1: about a hundred and fifteen days in the host's body 56 00:03:13,320 --> 00:03:16,320 Speaker 1: and will eventually be completely replaced by red blood cells 57 00:03:16,400 --> 00:03:20,079 Speaker 1: carrying their original genetic code. These types of chimerism are 58 00:03:20,080 --> 00:03:23,320 Speaker 1: commonly known as microchimerism, and one of the most frequent 59 00:03:23,360 --> 00:03:27,760 Speaker 1: causes is pregnancy. Trace fetal stem cells often remain in 60 00:03:27,760 --> 00:03:30,560 Speaker 1: a mother long after she has given birth. Some of 61 00:03:30,600 --> 00:03:32,880 Speaker 1: these stem cells have even been found to reside in 62 00:03:32,880 --> 00:03:36,520 Speaker 1: women's brains. Likewise, a pregnant woman's cells can cross the 63 00:03:36,520 --> 00:03:40,240 Speaker 1: placenta and become part of their child's liver, heart, thymus, gland, 64 00:03:40,280 --> 00:03:45,120 Speaker 1: and bloodstream. Many people may not ever suspect that microchimerism 65 00:03:45,240 --> 00:03:47,920 Speaker 1: is part and parcel of their existence, but it's probably 66 00:03:47,920 --> 00:03:51,960 Speaker 1: more frequent than we realize. In fact, chimerism, both tetragametic 67 00:03:52,040 --> 00:03:55,960 Speaker 1: and micro may someday challenge how medicine, forensics, and even 68 00:03:56,000 --> 00:04:00,120 Speaker 1: the legal system contend with DNA. DNA testing, which is 69 00:04:00,160 --> 00:04:04,400 Speaker 1: done by collecting small amounts of human saliva, semen, hair, bone, blood, 70 00:04:04,480 --> 00:04:07,520 Speaker 1: or skin tissue, relies on the notion that every cell 71 00:04:07,600 --> 00:04:11,560 Speaker 1: in an individual body contains identical DNA, and that each 72 00:04:11,640 --> 00:04:16,080 Speaker 1: person has different DNA chimerism challenges the notion of a 73 00:04:16,160 --> 00:04:20,560 Speaker 1: one DNA to one person system. In one complex assault case, 74 00:04:20,600 --> 00:04:23,640 Speaker 1: for example, evidence at the scene matched a DNA blood 75 00:04:23,640 --> 00:04:28,000 Speaker 1: sample from a criminal already profiled in a law enforcement database. However, 76 00:04:28,120 --> 00:04:31,120 Speaker 1: this person was in jail when the assault occurred. To 77 00:04:31,160 --> 00:04:34,359 Speaker 1: make matters even more confusing, the DNA blood sample also 78 00:04:34,400 --> 00:04:37,400 Speaker 1: matched the DNA profile of another person who could also 79 00:04:37,440 --> 00:04:41,279 Speaker 1: have been implicated in the crime. After investigating, it was 80 00:04:41,320 --> 00:04:44,080 Speaker 1: determined that the two men were brothers. The man in 81 00:04:44,160 --> 00:04:47,760 Speaker 1: jail had previously received a bone marrow transplant from his brother. 82 00:04:48,320 --> 00:04:51,120 Speaker 1: This means that the jailed man was a chimera. His 83 00:04:51,160 --> 00:04:54,239 Speaker 1: blood DNA profile matched that of his brother's blood DNA, 84 00:04:54,560 --> 00:04:58,240 Speaker 1: while his saliva DNA profile was distinctly his own. In 85 00:04:58,279 --> 00:05:01,360 Speaker 1: the end, investigators used a blood sample and cheek swab 86 00:05:01,440 --> 00:05:03,200 Speaker 1: to make a d n A match from the crime 87 00:05:03,240 --> 00:05:11,520 Speaker 1: scene and charged the correct brother with the crime. Today's 88 00:05:11,520 --> 00:05:14,080 Speaker 1: episode is based on the article calimerism you Can be 89 00:05:14,120 --> 00:05:16,400 Speaker 1: your Own twin on how stuff Works dot Com, written 90 00:05:16,440 --> 00:05:18,920 Speaker 1: by Laur L. Dove. Brain Stuff is production of I 91 00:05:18,960 --> 00:05:21,080 Speaker 1: Heart Radio in partnership with how stuff works dot Com, 92 00:05:21,200 --> 00:05:24,000 Speaker 1: and it is produced by Tyler Clang four more podcasts 93 00:05:24,000 --> 00:05:26,160 Speaker 1: from my heart Radio. Visit the i heart Radio app, 94 00:05:26,279 --> 00:05:29,040 Speaker 1: Apple podcasts, or wherever you listen to your favorite shows.