Understanding Chimerism And Responses To It Biology Essay


In 1998, Margot Kruskall, a doctor at the Beth Israel Deaconess Medical center in Boston, and his team discovered a weird abnormality known as Chimera. Jane, a 52 years old lady, underwent a genetic testing for a possible kidney transplant with her three children to check for a fitting donor. Surprisingly, the tests determined that two of them weren't her biological kids. The parents assured that they haven't undergone a vitro-fertilization, nor a mix-up of babies occurred, because the three kids had the genes of their dad (Wood, 2006, Para.2). Subsequent to two long years of experiments and tests, Kruskall and his team figured out an answer to the mystery. After DNA tests from different tissues in Jane's body, they found out that she has two different sets of DNA, which resulted in a conclusion that: "Jane was a mixture of two different people (New Scientist vol 180 issue 2421, 2003, Pg.34)."

Chimera is a creature from the Greek legend known to be a fire breathing monster with a lion head, a goat body and a serpent tail (Wood, 2006, Para.3). While on the other hand, the biological Chimerism (Chimera) is a term used to identify the abnormality of an organism that contains more than one set of DNA. Both the strange abnormality and the Greek legend are called Chimeras because of the mutation of more than one population.

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A human Chimera's story begins as fraternal twin in their zygotes stage. Two siblings developing from two different eggs and sperms start absorbing each other till they combine forming one fetus. Each of these twins keeps their own characteristics which result in the formation of a creature with a mixture of tissues (Wiki, 2010, Para.1).This abnormality is usually inherited or acquired through transplantation or transfusion. surprisingly, "Chimeras can often breed, but fertility and type of offspring depends on which cell line gave rise to the ovaries and testes; varying the degree of intersexuality may result if one set of cells is genetically female and another is genetically a male (Wiki, 2010, Para.2)."

Chimera is found in many different forms. The most common form is the blood chimera. Most kids and fraternal twins share a small portion of blood with either their twin or mother forming a new tissue found in the bone marrow (MedicineNet, 2010, Para.1 &2). That form makes most of us, if not all, Chimeras. However, each mother, kid and twin is genetically different, except that they share the same blood (Wood, 2006, Para.4). In the mother and son case, Nelson and Natalie Lambert believed that the blood from the mom can be a helping hand. She believed: "the maternal cells are there trying to repair the damaged tissue (New Scientist vol 180 issue 2421, 2003, Pg.34.)"

Another common form of Chimera is the Germline Chimerism. This form occurs between germ cells (sperms and eggs) that aren't genetically identical. They allow them to carry reproductive cells of their twins, and most of the time they give birth to their twin's children (Anitei, 2007, Para.1 & 2). Jane's case was a Germline Chimerism; she carried both of her and her sister's ovaries.

Most people go through life without realizing they're Chimeras. "They are probably dramatically under diagnosed, and also dramatically rare," Kruskall said. In Most cases it's completely unnoticeable till the time they do genetic tests, or certain spectrums of UV light X-rays. However, in some rare cases, Chimerians might have different phenotypes. They might have slightly different eye color or different hair growth on different sides of the body. They can also have pigmentation irregularities because of the different DNA that appears under UV light. It shows two different shades of skin, patterned like cat stripes, known as Blashko's Lines (Son, 2010, Para.10).

The previous symptoms have no affect on the person's abilities, nor his organisms. However some affects can change many things in a Chimera's life. Most people with Germline Chimerism form a combination of ovotestes, which are noticeable most of the time for having a mixture of both a female and male characteristics. Furthermore, some parents can give birth to their twin's biological kids and not know till they do genetic tests (Son, 2010, Para.14).

Chimerism is one of the diseases with no treatments. As I mentioned before, in some cases people won't even realize they're Chimeras. However in some rare cases, a person will be able to get rid of his twin's organ if he's capable of living without it. In episode two, season three of House, a patient suffering from strange symptoms such as bleeding disorders; believes he can see aliens attacking him. They expected it to be a hallucination; however, after a long investigation house figured out that kid is a Chimera with two sets of DNA in his body and has abnormal brain cells. As a solution House preformed a brain surgery and removed those cells.

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This disease won't develop if it's untreated, except a person with the Germline form. In a Germline form a mother is able to give birth to her sibling's children; and a male can pass on his brother's sperms instead of his own. Furthermore, rare conditions of hermaphrodism can occur, and be obvious in his physical appearance and might suffer from intersexuality (Son, 2010, Para.11).

b) Interactions of the genes and the environment:

Chimerism is known to be a genetic disease that is either inherited or transferred through transplantation and transfusion. Different people around the world might react to this disorder from different perspectives. Some might not understand the disorder, and might also not know that it's biological. They won't realize that that person isn't able to escape from it, even though he's living a normal life. They might be rude and annoy the victim of Chimera. They may also tease him and insult him if he's suffering from some palpable symptoms. What they aren't aware of is that they might be victims of the same disorder too.

Those misunderstanding people are usually the ones living in western, closed societies. They're the ones not exposed to the proper education and to the real life. They aren't capable of understanding the world and the material in it, which will also not allow them to understand disorders and diseases.

On the other hand, educated understanding people and scientist will understand the case well. They'll treat that person like any other person, and will respect their dignity. However, if that person is suffering from obvious symptoms such as some conditions of intersexuality; those understanding people will try to provide them with the proper environment to live in, and will make sure they're living like any other person. Furthermore, those educated people and scientists might be interested in their case, and might aim to research that person to get more information about the disorder.

Part 2:

a) Case History

On July 24, 2009; M.D., a patient of multiple myeloma, the cancer of plasma cells, approached me with her mother and two kids to check for a possible Allogeneic bone marrow transplant. Allegoneic bone marrow transplant means taking stem cells from a donor's bone marrow that has similar genetic typing as the patient.

I started with tests to ensure that M.D. is physically capable of undergoing the transplant, and followed that by other tests for certain organ functions. When all the tests gave healthy results, M.D, her mom, and her two kids were asked to take the saliva test to check for matching genes.

Surprisingly, her two kid's genes didn't match any of her own. I asked them to undergo other genetic tests expecting that an error accord during the test. At first, my prediction was confirmed; the second genetic test matched the genes of the two kids which meant they're able to undergo a bone marrow transplant. However, more genetic tests we're taken to assure that they match. Surprisingly, my prediction didn't stay true for long, different genetic tests had both sets of genes. This made it much complicated, especially when both sets matched the grandma's while only one matched the two kids.

We made sure M.D. didn't know what's going own fearing her health statues will get worse. And continued testing, aiming to discover what's going wrong. Detailed family and clinical questions were asked to all members of the family. M.D.'s mom claimed that she underwent vitro fertilization because of certain problems in her fallopian tube. And it was assured that no baby switching occurred at birth, because the two kids had their father's genes and shared genes with their grandma. Plus, that in some gene tests, they matched their mom's genes.

b) Diagnosis:

After a long period of tests and x-rays nothing important showed, except some pigment irregularities on M.D.'s skin that showed under the UV light that I thought are unimportant. I thought they're a result of a failed skin treatment, or because of extra making of the skin's melanin.

At first, I diagnosed that a switching of babies occurred at birth, but that wasn't possible because of the DNA of both the father and the grandma. And it's a rare chance that two baby switching will occur with two siblings. There was no other possible explanation except Chimerism. I took different samples from her two ovaries, and checked for their DNA. As predicted, they had two different sets of genes which assured its Chimerism. One ovary matched the genes of her kids while the other didn't, however both matched the mom because they're twins.

c) Treatment:

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Most cases of Chimerism have no treatments and M.D.'s case in one of them. She's been living her entire life with her, and her sister's ovary without knowing, and continuing her life with them won't affect her. She wasn't suffering from any pain, and if they don't mention it to her she won't know. However, lucky her, her genes matched her mom's and she was able to get a bone marrow transplant from her to cure her Myeloma.

d) Prognosis:

Because no cure was given to M.D., I think not telling her is the best way she can cope with this disease. Even though she has given birth to them, theyaren't biologically her kids and that'll be depressing to know. Whether she knew or not, that won't affect her health, however if she gets depressed it might affect her, especially that she's suffering from Myeloma.

However, if they insist on telling her, the two kids must assure to her that nothing will change, and that she's their mother no matter what. She carried them nine months and she's the one that raised them. All the family must stand by her side, and give her all she needs to accept what she's going through.

Part 3:

Reaction & response to the disorder:

Chimera is one of the grossest disorders that I've ever heard of. The Idea of you having someone else's set of DNA, especially the ovaries or testis, makes me want to vomit. However, it's a fascinating disorder that I never thought is possible. Its magical how one fetus can absorb the other and make him part of him and live with that different tissue without even knowing. It's also a sad disorder when a mother gives birth to her sister's kid without even realizing, and raising them as if they're her own. Or when a person has a mixture of both a female and male characteristics, and is forced to adapt to that, especially when the society he's living in doesn't accept him.

In most cases it won't be difficult to live with that disorder, because in most cases it won't even be diagnosable. However, it can be difficult for the patient, his parents, or spouse if he's suffering from the Germline Form. As I mentioned above, the patient might not accept the idea of giving birth to a kid of different DNA, or have someone else's germ cells in him. It might also be hard if he's intersexual and is forced to adapt to his community. Nevertheless, parents will also have a hard time with their chimera kid. They'll feel bad if they're kids are, and will suffer when they do. They will have a hard time if the kid's suffering from intersexuality knowing it's something he can't solve, and they can't help. And it'll be sad to have a kid that's different from the kids around him. Furthermore, that Germline Chimera might have a hard time finding a spouse if he's intersexual. And the spouse, in most cases, won't accept the idea of having kids with the DNA of his sister's wife.

Reaction & response to the Project:

Despite my response to the disorder, I think that it was a really interesting project that taught me many stuff. Besides what it taught me, it awakened me to the many diseases found all around the world that we have never heard of and never thought they might exist. And no matter how rare or common they are, and how obvious they can be, they're sometimes really painful and change many people's lives. That makes me happy and pleased with what I have, and stops me from complaining, especially when I imagine how hard other people's lives can be. Furthermore, I understood that people can seriously be suffering from intersexuality, and that it's something they're forced to live with, and unable to solve. Everyone has to understand that point and stop bothering them, because what they're going through is more than enough and it's not their choice.

While researching this disease, I had a hard time finding good resources because they all had the exact same information, and most of them weren't credible. Besides, many discussed the Greek creature instead of discussing the disorder.

Even though at the beginning I was bothered with the idea that I have to right an entire research paper about a disease I've never heard before; I find it an interesting way of learning, and an intriguing project. However, it'll be more interesting if we get the chance to present it to the class, because I believe we all have to have the chance of knowing more about diseases around us. Plus it'll be really appealing if others understood Chimerism and how it develops.