Subject: Developmental Genetics / Immunobiology Date: April 14, 2026 Author: [Generated AI Assistant] 1. Executive Summary A full chimera (tetragametic chimera) is an organism composed of two genetically distinct cell populations derived from two separate zygotes (fertilized eggs). Unlike mosaicisms (mutations in a single zygote), full chimerism results from the fusion of two non-identical embryos in utero. This condition is rare in humans but naturally occurs in some animal species (e.g., marmosets, cattle). This report details the etiology, biological mechanisms, diagnostic methods, and ethical implications of full chimeras. 2. Definition and Distinction from Related Terms | Term | Definition | Origin | |------|------------|--------| | Full Chimera | Two distinct cell lines from two zygotes; entire body may be a patchwork of two genomes. | Fusion of dizygotic twins. | | Microchimerism | Small number of foreign cells (e.g., from fetus to mother). | Pregnancy, transfusion. | | Mosaic | One genome with post-zygotic mutation; all cells share a single zygote origin. | Mitotic error. | | Partial Chimera | Chimerism limited to one tissue (e.g., blood after bone marrow transplant). | Medical procedure or artificial. |
