blood chimera

genetics

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July 20, 2026

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A chimera, in genetics, is an organism or tissue containing at least two different sets of DNA, often from the fusion of different zygotes. This differs from mosaics, which arise from a single zygote, and hybrids, which result from crossing different species.1

A notable type is the blood chimera, where dizygotic twins exchange stem cells through placental blood connections. This can lead to conditions like freemartin syndrome in cattle, where a female is masculinized by male hormones from her twin. In humans, blood chimerism may be detected through blood typing.1

Microchimerism involves fetal or maternal cells crossing the placenta or transfer through transfusions or transplants. Its significance is still being researched, with potential links to immune responses and autoimmune disorders.1

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chimera
…examples of twin chimerism are blood chimeras. These individuals are produced when blood anastomoses (connections) form between the placentas of dizygotic twins, thereby enabling the transfer of stem cells between the developing embryos. When blood chimerism involves male and female twins, female exposure to male hormones results in
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…examples of twin chimerism are blood chimeras. These individuals are produced when blood anastomoses (connections) form between the placentas of dizygotic twins, thereby enabling the transfer of stem cells between the developing embryos. When blood chimerism involves male and female twins, female exposure to male hormones results in
Read More