The main difference between mosaicism and chimerism is that mosaicism involves a small genetic change whereas chimerism involves a much larger genetic change.
Mosaicism and chimerism are two types of genetic changes in the genome, resulting in two or more genetically distinct populations of cells.
Key Areas Covered
- What is Mosaicism
- Definition, Characteristics, Importance
- What is Chimerism
- Definition, Characteristics, Importance
- Similarities Between Mosaicism and Chimerism
- Outline of Common Features
- Difference Between Mosaicism and Chimerism
- Comparison of Key Differences
Key Terms
Chimerism, Mosaicism
What is Mosaicism
Mosaicism is a condition in a multicellular organism in which the organism presents more than one genetic line. The main cause of mosaicism is a genetic mutation. Therefore, different genetic lines occur in a single individual arising from a single fertilized egg. The main types of genetic mutations that lead to mosaicism include chromosome nondisjunction, endoreplication, and anaphase lag. Anaphase lagging is the most common method by which mosaicism arises in the preimplantation embryo.
Figure 1: Mosaicism in Tulip
Furthermore, there are two types of mosaicism: they are germline mosaicism and somatic mosaicism. Germline mosaicism occurs in gametes: sperms or oocytes. This occurs due to the mutations in the early stem cells. In contrast, somatic mosaicism occurs due to the mutations that occur in somatic cells. However, germline mosaicism is passed down to the next generation while somatic mosaicism is not inheritable.
What is Chimerism
Chimerism is the presence of two or more genotypes in the same individual. Generally, it arises from the fusion of more than one fertilized zygote in the early stages of embryonic development. On the other hand, artificial chimerism occurs in organ transplantation due to the presence of donor cells with different cell populations. On the other hand, twin chimerism occurs due to the presence of more zygotes. Zygotes with different sexes are also a type of chimerism.
Figure 2: Chimerism in African Violet
Moreover, chimerism in animals occurs due to the presence of two or more different populations of genetically distinct cells that originated from different zygotes. Since each population of cells keep its own character, organisms result in a mixture of genotypes in a particular tissue.
Similarities Between Mosaicism and Chimerism
- Mosaicism and chimerism are two genetic changes in the genome.
- In both conditions, an individual contains cell populations of two or more different genomes.
Difference Between Mosaicism and Chimerism
Definition
Mosaicism refers to the property or state of being composed of cells of two genetically different types while chimerism refers to a single organism composed of cells with more than one distinct genotype.
Significance
Usually, mosaicism is the presence of more than one genome in a single individual while chimerism is the presence of two or more genotypes.
Occurrence
Mosaicism occurs due to somatic mutations in a single fertilized egg while chimerism occurs due to the fusion of more than one fertilized zygote.
Degree of genetic Change
Mosaicism has a less degree of genetic change while chimerism has a higher degree of genetic change.
Conclusion
In brief, mosaicism is the presence of more than one type of genome in a single individual. More importantly, it arises from the somatic mutations of a particular individual that arises from a single unfertilized egg. Chimerism, on the other hand, is the presence of more than one genotype in a particular individual. It occurs due to the fusion of more than one fertilized zygote. Hence, the genetic change is higher in chimerism in comparison to mosaicism. On that account, the main difference between mosaicism and chimerism is the formation of genetic change.
References:
- “Mosaic (Genetics).” Wikipedia, Wikimedia Foundation, 10 Oct. 2022.
- “Chimera (Genetics).” Wikipedia, Wikimedia Foundation, 9 Oct. 2022.
Image Courtesy:
- “Tulip with mosaicism” By Paddlestroke – Own work (CC BY-SA 4.0) via Commons Wikimedia
- “African violet chimeras” By G00251 – Own Work (CC BY-SA 4.0) via Commons Wikimedia
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