What Is The Genetic Makeup Of Identical Twins
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Research published on January 7 in the journal Nature Genetics shows that identical twins differ by an average of 5.2 genetic mutations. The authors argue that these small differences between twins' genetic code could alter how scientists study human being development.
The study of 381 pairs of identical twins and 2 sets of identical triplets found that only 38 were genetically identical, Tina Hesman Saey reports for Science News. Nigh had just a few points of genetic mismatch, only 39 had more than 100 differences in their DNA. The findings could impact future studies of the ways that the surround affects illness and human development. In such studies, scientists frequently assume that pairs of identical twins have identical DNA, so their differences can be explained by the environments they grew up in.
"Before y'all can make that interpretation, you'd better brand sure that one of them does not have a de novo [randomly introduced] mutation in an important gene that the other ane does non," says Kari Stefansson, CEO of DeCODE Genetics and pb author of the new study, to the Scientist mag'southward Catherine Offord. "Then this certainly places a new kind of brunt on those who utilize identical twins to plant the separation between nature and nurture."
The researchers sequenced the full Deoxyribonucleic acid code of cells found in cheek swabs and blood samples from not but the twins, but also their parents, their children, and their children'due south other parent, Nicoletta Lanese reports for Alive Science. With iii generations of genetic information, the researchers could non only figure out where specific mutations appeared in the Deoxyribonucleic acid code, only when, by determining at what stage in their embryonic evolution the mutations occurred.
The genetic mutations observed in the study mostly involved a single edifice block of the Dna code, called a base, mistakenly swapped for a different ane. In some cases, letters were either inserted or deleted. Working at the scale of a human genome, a few changes may non cause much of a deviation.
"Such genomic differences between identical twins are still very rare," says Academy of Pennsylvania computational biologist Ziyue Gao, who wasn't involved in the study, to Alive Science. The human genome is six billion base pairs long, and the report did not make it clear how many of the mutations would crusade significant changes. She adds, "I uncertainty these differences will accept appreciable contribution to phenotypic [or observable] differences in twin studies."
The mutations covered in the study tend to appear while a cell is replicating, or dividing itself, to create more than cells. During that procedure, the prison cell has to completely re-create all six billion base pairs, and sometimes it makes mistakes. The cell has machinery to correct mistakes, simply even those go incorrect sometimes, leaving behind small typos. If such a typo is created in a parcel of cells early on in homo evolution, then when the package splits into two parts, the mutation might not attain both parts as.
"Nosotros accept establish a twin pair where one of the twins has mutations in all cells of his body, and they are not establish in any cell in the body of the other twin. That ways basically that one of the twins is formed solely from the descendant of the prison cell where the mutation took identify," says Stefansson to the Scientist. "So we have establish twins when the mutation is found in all cells in the torso of 1 of the twins, and in 20 percent of the cells in the trunk of the other twin. And so 1 of the twins has just formed from the descendant of this one jail cell where the mutation happened, and the other is formed in part by descendants of that cells and in role by something else."
The written report compared the twins' DNA to their parents and children to find out when the mutation happened during their development. If the mutation happened very early, then the mutation could be passed along to their children, because information technology would have ended upward in their sperm or eggs. Mutations that happen later in embryonic development might simply announced in a person'southward non-reproductive cells.
Uppsala University geneticist January Dumanski tells the Associated Press' Christina Larson that the report is "a articulate and important contribution" to medical research.
Stefansson adds that the implications get beyond nature-and-nurture twin studies.
"This is not only a study that has relevance when information technology comes to agreement of the genetics, but also human evolution: How do nosotros probe early homo evolution in an ethical way, a non-interventional manner? This is one manner of doing that," he says to the Scientist magazine. "We can begin to use the mutations to develop [an] understanding of how cells are allocated from the early embryo to develop the various organs in the body."
What Is The Genetic Makeup Of Identical Twins,
Source: https://www.smithsonianmag.com/smart-news/identical-twins-can-have-slightly-different-dna-180976736/
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