Identical Twins: Not as Identical as We Thought
Identical twins are often thought to be genetically identical, but new research shows that this is not entirely true. As twins grow and develop, they can acquire their own unique set of mutations, which can lead to significant genetic differences between them.
Somatic Mutations in Identical Twins
Somatic mutations are mutations that occur in the cells of the body after conception. These mutations can arise during cell division or as a result of exposure to environmental factors such as radiation or chemicals.
A study conducted by Rui Li at McGill University found that an average twin pair has 359 somatic mutations in their genome, all of which occurred during early development. These mutations can affect a variety of genes, including genes that are involved in physical appearance, disease susceptibility, and behavior.
Other Genetic Differences Between Identical Twins
In addition to somatic mutations, identical twins can also differ in other genetic ways. For example, one twin may have a different number of copies of a particular gene than the other twin. This is known as a copy number variant (CNV).
CNVs can have a significant impact on health outcomes. For example, one twin in a study by Carl Bruder of the University of Alabama at Birmingham was missing some genes on particular chromosomes that indicated a risk of leukemia, which he indeed suffered. The other twin did not have these missing genes and did not develop leukemia.
Implications for Twin Studies
The fact that identical twins are not actually genetically identical has important implications for twin studies. Twin studies are often used to investigate the role of genes and environment in complex diseases such as schizophrenia and autism.
If identical twins are not genetically identical, then it is more difficult to determine the extent to which genes contribute to these diseases. Additionally, it may be more difficult to use identical twins as a control group in studies of environmental risk factors.
Conclusion
The discovery that identical twins are not as genetically identical as we once thought has significant implications for our understanding of genetics and disease. It is important to consider these genetic differences when interpreting the results of twin studies and when making decisions about medical care for identical twins.
How Many Somatic Mutations Occur in Identical Twins During Early Development?
A study conducted by Rui Li at McGill University found that an average twin pair has 359 somatic mutations in their genome, all of which occurred during early development.
What Are the Genetic Differences Between Identical Twins?
In addition to somatic mutations, identical twins can also differ in other genetic ways, such as:
- Copy number variants (CNVs): One twin may have a different number of copies of a particular gene than the other twin.
- Mitochondrial DNA (mtDNA): mtDNA is passed down from mother to child, and identical twins can have different mtDNA sequences if they inherited different mtDNA from their mother.
- Epigenetic modifications: These are changes to the DNA that do not change the underlying sequence, but can affect gene expression.
How Can Genetic Variations Affect the Health Outcomes of Identical Twins?
Genetic variations between identical twins can affect their health outcomes in a number of ways. For example, one twin may be more susceptible to a particular disease than the other twin, or they may respond differently to the same treatment.
What Are the Limitations of Using Identical Twins in Genetic Studies?
The fact that identical twins are not actually genetically identical has limitations for using them in genetic studies. For example, it can be more difficult to determine the extent to which genes contribute to complex diseases, and it may be more difficult to use identical twins as a control group in studies of environmental risk factors.
Can Identical Twins Get Away with Murder Due to Their Genetic Similarities?
There is no evidence to suggest that identical twins can get away with murder due to their genetic similarities. While identical twins may share many physical and genetic characteristics, they are still two separate individuals with their own unique thoughts, feelings, and motivations.