Chimerism
The presence of cells or tissues from two individuals, chimeras, or the presence of cells and tissues that include the gonads, tetragametic chimerism can be detected by the analysis of cytogenetics and analysis of polymorphic genetic markers, using patterns of pedigree inheritance. These methodologies include determination of sex chromosomes, major histocompatibility complex (MHC) polymorphisms and panels of short tandem repeats(STRs) that include mitochondrial DNA markers.
A genetic chimerism or chimera (also spelled chimera) is a single composed of cells with distinct genotypes. In animals, this means an individual derived from different Zygotes, which can include possessing both female and male sex organs, blood cells of two blood types, or subtle variations in form. Animals chimeras are produced by the merger of multiple fertilized eggs.
In plants chimeras, however, the distinct types of tissue may originate from the same zygote, and the difference is often due to mutation during ordinary cell division. Normally, genetics chimerism is not visible on casual inspection, however, it has been detected in the course of proving parentage. Another way that chimerism can occur in animals is by organ transplantation, giving one individual tissue that developed from a different genome. For example, transplantation of bone marrow often determines the recipient's ensuing blood type.
This condition is either inherited or it is acquired through the infusion of allogeneic hematopoietic cells during transplantation or transfusion. In non-identical twins, chimerism occurs by means of blood- vessel anastomoses. The likelihood of offspring being a chimera is increased if it is created via in vitro fertilization. Chimeras can often breed, but the fertility and type of offspring depend on which cell line gave rise to the ovaries or testes, varying degrees of intersex differences may result if one set of cells is genetically female and another genetically male.
Tetragametic Chimerism:
Tetragametic chimerism is a form of congenital chimerism. This condition occurs through the fertilization of two separate ova by two sperm. followed by aggregation of the two at the blastocyst or Zygote stages.
This results in the development of an organism with intermingled cell lines put another way, the chimera is formed from the merging of two non-identical twins( a similar merging presumably occurs with identical twins, but as their genotypes are not significantly distinct, the resulting individual would not be considered a chimera.) As such, they can be male, female, or have mixed intersex characteristics.
Natural chimeras are almost never detected unless they exhibit abnormalities such as male/female or hermaphrodite characteristics or uneven skin pigmentation. The most noticeable are some male tortoiseshell cats(although most male tortoiseshells have an extra X chromosome responsible for the coloration) or animals with ambiguous sex organs.
The existence of chimerism is problematic for DNA testing, a fact with implications for family and criminal law. The Lydia Fairchild case, for example, was brought to court after DNA testing apparently showed that her children could not be hers. Fraud charges were filed against her and her custody fo her children was challenged. The charge against her was dismissed when it became clear that Lydia was a chimera, with the matching DNA being found un her cervical tissue. Another case was that of Karen Keegan, who was also suspected (initially) of not being her children's biological mother, after DNA tests on her adult sons for a kidney transplant she needed seemed to show she wasn't their mother.
Microchimerism:
Microchimerism is the presence of a small number of cells that are genetically distinct from those of the host individual. Most people are born with a few cells genetically identical to their mother's and the proportion of these cells goes down in healthy individuals as they get older. People who retain a higher number of cells genetically identical to their mothers have been observed to have higher rates of some autoimmune diseases, presumably because the immune system is responsible for destroying these cells and a common immune defect prevents it from doing so and also causes autoimmune problems.
Germline Chimerism:
Germline Chimerism occurs when the germ cells(for example, sperm and egg cells )of an organism are not genetically identical to its own. It has recently been discovered that marmostes can carry the reproductive cells of their twin siblings, because of placental fusion during development.
Humans:
The Dutch sprinter Foekje Dilemma was expelled from the 1950 national team after she refused a mandatory sex test in July 1950, later investigation revealed a Y- chromosome in her body cells, and the analysis that she probably was a 46, XX/46 XY mosaic female.
In 1953 a human chimera was reported in the British Medical Journal. A woman was found to have blood containing two different blood types. Apparently, this resulted from her twin brothers cells living in her body. A 1996 study found that such blood group chimerism is not rare.
Chromosomal Chimeras:
These are chimeras in which the layers differ in their chromosome constitution. Occasionally fragments owing to misdivision. More commonly cytochimeras have simple multiple of the normal chromosome complement in the changed layer. There are various effects on cell size and growth characteristics.
Nuclear Gene- differential Chimeras:
These chimeras arise by spontaneous or induced mutation of a nuclear gene to a dominator recessive allele. As a rule, one character is affected at a time in the leaf, flower, fruit, or other parts.
Plastid Gene- differential chimeras:
These chimeras arise by spontaneous or induced mutation of a plastid gene, followed by the sorting-out of two kinds of plastid during vegetative growth. Alternatively, after selfing or nucleic acid thermodynamics, plastids may sort-out from a mixed egg or mixed zygote respectively.
women born with unique birthmark learns she's her together in the womb.
Ever since Taylor Muhl was a little girl, she longed to have a twin sibling. The singer and model would often asl for mother whether she was a twin and became obsessed with dressing just like her friends. Years later, Muhl learned that she wish had already come true. The Los Angeles native grew up believing a discoloration on her stomach was simply a birthmark, and after years of battling autoimmune issues, Muhl went to a doctor who diagnosed her with chimerism, a rare disorder in which a person has two sets of DNA. In Muhl's case, she lives with the DNA of her fraternal twin whom she absorbed in her mother's womb.
“I actually felt relief. I felt free because for the first time in my life I knew why my stomach looks the way it does. This is why I’ve had so many health challenges,” the model says of coming to term with the news. “I felt like for the first time I could really breathe. Prior to that, every doctor said my stomach must have just been a birthmark … Finally, this is making some sense.”
Muhl says her mother, who didn't have more children, was saddened by the news. viewing the situation as"losing a child".
Now, Muhl focuses on living a healthy, active lifestyle to cope with her condition.Although she has known about her disorder for several years, she only went public with the news last year. Muhl says she kept her condition private, and hid her stomach, in fear of losing opportunities in the entertainment industry.
“This has probably been the most freeing year that I have ever lived in my entire life. What was so hard for me was pretending that I wasn’t sick and it’s something that I did for the last seven-plus years. It really does start wearing on you. Now I don’t have to worry about any of it. It’s all out there.”
The presence of cells or tissues from two individuals, chimeras, or the presence of cells and tissues that include the gonads, tetragametic chimerism can be detected by the analysis of cytogenetics and analysis of polymorphic genetic markers, using patterns of pedigree inheritance. These methodologies include determination of sex chromosomes, major histocompatibility complex (MHC) polymorphisms and panels of short tandem repeats(STRs) that include mitochondrial DNA markers.
A genetic chimerism or chimera (also spelled chimera) is a single composed of cells with distinct genotypes. In animals, this means an individual derived from different Zygotes, which can include possessing both female and male sex organs, blood cells of two blood types, or subtle variations in form. Animals chimeras are produced by the merger of multiple fertilized eggs.
In plants chimeras, however, the distinct types of tissue may originate from the same zygote, and the difference is often due to mutation during ordinary cell division. Normally, genetics chimerism is not visible on casual inspection, however, it has been detected in the course of proving parentage. Another way that chimerism can occur in animals is by organ transplantation, giving one individual tissue that developed from a different genome. For example, transplantation of bone marrow often determines the recipient's ensuing blood type.
This condition is either inherited or it is acquired through the infusion of allogeneic hematopoietic cells during transplantation or transfusion. In non-identical twins, chimerism occurs by means of blood- vessel anastomoses. The likelihood of offspring being a chimera is increased if it is created via in vitro fertilization. Chimeras can often breed, but the fertility and type of offspring depend on which cell line gave rise to the ovaries or testes, varying degrees of intersex differences may result if one set of cells is genetically female and another genetically male.
Tetragametic Chimerism:
Tetragametic chimerism is a form of congenital chimerism. This condition occurs through the fertilization of two separate ova by two sperm. followed by aggregation of the two at the blastocyst or Zygote stages.
This results in the development of an organism with intermingled cell lines put another way, the chimera is formed from the merging of two non-identical twins( a similar merging presumably occurs with identical twins, but as their genotypes are not significantly distinct, the resulting individual would not be considered a chimera.) As such, they can be male, female, or have mixed intersex characteristics.
Natural chimeras are almost never detected unless they exhibit abnormalities such as male/female or hermaphrodite characteristics or uneven skin pigmentation. The most noticeable are some male tortoiseshell cats(although most male tortoiseshells have an extra X chromosome responsible for the coloration) or animals with ambiguous sex organs.
The existence of chimerism is problematic for DNA testing, a fact with implications for family and criminal law. The Lydia Fairchild case, for example, was brought to court after DNA testing apparently showed that her children could not be hers. Fraud charges were filed against her and her custody fo her children was challenged. The charge against her was dismissed when it became clear that Lydia was a chimera, with the matching DNA being found un her cervical tissue. Another case was that of Karen Keegan, who was also suspected (initially) of not being her children's biological mother, after DNA tests on her adult sons for a kidney transplant she needed seemed to show she wasn't their mother.
Microchimerism:
Microchimerism is the presence of a small number of cells that are genetically distinct from those of the host individual. Most people are born with a few cells genetically identical to their mother's and the proportion of these cells goes down in healthy individuals as they get older. People who retain a higher number of cells genetically identical to their mothers have been observed to have higher rates of some autoimmune diseases, presumably because the immune system is responsible for destroying these cells and a common immune defect prevents it from doing so and also causes autoimmune problems.
Germline Chimerism:
Germline Chimerism occurs when the germ cells(for example, sperm and egg cells )of an organism are not genetically identical to its own. It has recently been discovered that marmostes can carry the reproductive cells of their twin siblings, because of placental fusion during development.
Humans:
The Dutch sprinter Foekje Dilemma was expelled from the 1950 national team after she refused a mandatory sex test in July 1950, later investigation revealed a Y- chromosome in her body cells, and the analysis that she probably was a 46, XX/46 XY mosaic female.
In 1953 a human chimera was reported in the British Medical Journal. A woman was found to have blood containing two different blood types. Apparently, this resulted from her twin brothers cells living in her body. A 1996 study found that such blood group chimerism is not rare.
Chromosomal Chimeras:
These are chimeras in which the layers differ in their chromosome constitution. Occasionally fragments owing to misdivision. More commonly cytochimeras have simple multiple of the normal chromosome complement in the changed layer. There are various effects on cell size and growth characteristics.
Nuclear Gene- differential Chimeras:
These chimeras arise by spontaneous or induced mutation of a nuclear gene to a dominator recessive allele. As a rule, one character is affected at a time in the leaf, flower, fruit, or other parts.
Plastid Gene- differential chimeras:
These chimeras arise by spontaneous or induced mutation of a plastid gene, followed by the sorting-out of two kinds of plastid during vegetative growth. Alternatively, after selfing or nucleic acid thermodynamics, plastids may sort-out from a mixed egg or mixed zygote respectively.
women born with unique birthmark learns she's her together in the womb.
Ever since Taylor Muhl was a little girl, she longed to have a twin sibling. The singer and model would often asl for mother whether she was a twin and became obsessed with dressing just like her friends. Years later, Muhl learned that she wish had already come true. The Los Angeles native grew up believing a discoloration on her stomach was simply a birthmark, and after years of battling autoimmune issues, Muhl went to a doctor who diagnosed her with chimerism, a rare disorder in which a person has two sets of DNA. In Muhl's case, she lives with the DNA of her fraternal twin whom she absorbed in her mother's womb.
“I actually felt relief. I felt free because for the first time in my life I knew why my stomach looks the way it does. This is why I’ve had so many health challenges,” the model says of coming to term with the news. “I felt like for the first time I could really breathe. Prior to that, every doctor said my stomach must have just been a birthmark … Finally, this is making some sense.”
Muhl says her mother, who didn't have more children, was saddened by the news. viewing the situation as"losing a child".
Now, Muhl focuses on living a healthy, active lifestyle to cope with her condition.Although she has known about her disorder for several years, she only went public with the news last year. Muhl says she kept her condition private, and hid her stomach, in fear of losing opportunities in the entertainment industry.
“This has probably been the most freeing year that I have ever lived in my entire life. What was so hard for me was pretending that I wasn’t sick and it’s something that I did for the last seven-plus years. It really does start wearing on you. Now I don’t have to worry about any of it. It’s all out there.”
Muhl often shares information about her condition, and even shows off her stomach on Instagram. She revealed her diagnosis in a post last year, boldly writing, “I’m a fraternal twin who fused together with my sibling in the womb.”
She tells PEOPLE: “I don’t have to hide who I am anymore and it’s a great feeling.”
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