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Home / Science / The model reveals a surprising disconnect between the physical characteristics and genetic ancestry of certain populations

The model reveals a surprising disconnect between the physical characteristics and genetic ancestry of certain populations



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A new study by biologists at Stanford University has found an explanation that physical characteristics such as skin pigmentation are “only the deep layers of the skin.”

; The research team used genetic models to find that when two populations with different characteristics merged over several generations, the characteristics of individuals in the resulting “mixed” population rarely reveal the individual’s ancestry.Their findings were published in a special edition on March 27 American Journal of Physical Anthropology About race and racism.

Jaehee Kim, a postdoctoral fellow in biology at Stanford University and the lead author of the study, said: “When the two founding groups first got together, the obvious physical characteristics between the founders initially contained information about the genetic ancestry of mixed individuals.” “But this research shows that after enough time, this is no longer true, and you can no longer determine a person’s genetic ancestry based on these characteristics alone.”

Diminishing correlation

In collaboration with Noah Rosenberg, professor of biology at Stanford University and others, King established a mathematical model to better understand genetic mixing-through this process, two long-separated populations come together, And created a third mixed population with ancestral roots from these two sources. They specifically studied how the relationship between physical properties and the level of genetic mixtures changes over time.

The researchers considered several scenarios. In a group, individuals in a mixed group mate randomly. In other cases, they are more likely to look for partners with similar genetic mix levels or similar trait levels in a process called “mating.”

Research has found that over time, characteristics that may initially indicate an individual’s genetic lineage eventually no longer have this information. If mating is random rather than random, although this decoupling of ancestors and traits occurs slower, decoupling will still occur in all cases.

Rosenberg, the senior author of the paper, said: “In this model, if the classification of mating depends on the inherited trait, the association between the trait and the genetic ancestor will last longer than if mating occurs randomly. But the association will eventually be dissociated.” He obtained the post of Professor of Population Genetics and Sociology at Stanford University in the School of Humanities and Sciences.

The team’s research was partly inspired by a study conducted by different teams in Brazil, which is a country with a long history of genetic confounding. After sampling individuals and studying their genomes, the biologist from a 2003 study assumed that there was a decoupling between physical features and genetic mixtures, and claimed that over time, features such as skin pigmentation are rare Reveal the proportion of ancestors from Europe, Africa, or Native American ancestry. The Stanford University research team found that their model largely supports this hypothesis.

Only skin deep

The researchers say that to understand this decoupling, one should consider a feature such as skin pigmentation, which is partly due to variation between a series of genes. If a person happens to have acquired most of their genetic pedigree from one population group, and the key genetic variation that determines their skin pigmentation from another population group, then their skin pigmentation does not seem to match their genetic pedigree . The reorganization of genetic variation that occurs in each generation increases the possibility of such mismatches.

Researchers recognize that their modeling methods have limitations. The model does not consider environmental conditions that also play a role in the development of traits. For example, a person’s height has a certain genetic basis, but it also depends on factors such as nutrition. The model only focuses on scenarios where the initial mixing occurs once, and does not explore the role of new members of the source population entering the mixed population over time. In the future, Rosenberg plans to add some of these features to the initial model.

Jin said that the new discoveries have important implications for understanding the social significance of physiological characteristics.

“When society assigns social significance to features such as skin pigmentation, the model shows that after mixing for enough time, the feature will not tell us much about genetic ancestry or other features based on heredity,” she said.


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More information:
Jaehee Kim et al., “Deep Skin: Decoupling Between the Level of Genetic Mixture and the Different Phenotypes of the Source Population, American Journal of Physical Anthropology (2021). DOI: 10.1002 / ajpa.24261

Provided by Stanford University



Citation: The model reveals a surprising disconnect between the physical characteristics and genetic lineage of certain populations (April 5, 2021), which was launched from https://phys.org/news/2021 on April 6, 2021 -04-reveals-disconnect-physical-characteristics-genetic.html

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