Mitochondrial DNA sometimes comes from fathers

Mitochondrial DNA sometimes comes from fathers
In a pioneering study rewriting textbooks, scientists found evidence of
patrilineal inheritance of mitochondrial DNA. Until recently, it was thought that
mtDNA could only be inherited from mothers.
Life is made up of millions of cells, and cells are made up of tiny functional
components called organelles. Mitochondria is a kind of organelle, which plays an
extremely important role in the normal operation of cells. Mitochondria, also known
as the "power station" of cells, produce chemical energy called ATP, which is
necessary for all biological processes in the body. Most of our DNA is stored in the
nucleus, but some are stored in mitochondria, called mitochondrial DNA (mtDNA).
Although in some species, such as flies and lice, mtDNA can also be inherited from
fathers, mitochondrial DNA is known to come only from mothers in humans. On the
other hand, nuclear DNA is inherited equally from both parents, meaning that
children will inherit 50% of nuclear DNA from each parent.
Like most cells, sperm contain many energy-producing mitochondria. Once the
sperm is fertilized by the egg, the mitochondria of the sperm break down in the
organelle membrane.
But the new study, led by geneticist Taosheng Huang, at the Children's Hospital
Medical Center in Cincinnati, turns down the common-sense view. The study began
in a four-year-old boy who developed symptoms of mitochondrial disorders. When
Huang and his colleagues tested the boy, they were surprised to find that their
mitochondrial DNA appeared to contain ingredients from their fathers. Of course,
this may seem impossible, but subsequent tests yielded the same results. When
evidence was found that the boy's sister and mother also had this heterogeneity
(multiple mitochondrial DNA variants from a single cell genomics source), Huang
knew he had discovered a new situation.
The researchers then sequenced the mtDNA of the boy's grandparents and
found that 60 percent and 40 percent of her mother's mtDNA came from her mother
and her father, respectively. Overall, the researchers found mitochondrial DNA
heterogeneity in three unrelated multigenerational families (17 individuals), ranging
from 24% to 76%. According to the study, the probability of this phenomenon is 1 in
5000 people.
The researchers were careful to point out that maternal inheritance in mtDNA
remains the norm, and these results are exceptions to this rule. However, it is not
clear what the proportion of such exceptions is. For example, the sequencing of
genes that had previously been found to be patrilineal in mitochondrial DNA was
thought to be wrong. These new findings suggest that they may not be just wrong.
Scientists are not sure how this patrilineal mtDNA permeates the embryo. What
they have determined is that this must be a genetic trait, especially since the
patient's mitochondria seem to have no defects. Whatever causes the father's
mitochondrial DNA to pass on to the offspring, it is likely to be a mutation in the
nucleus, because the DNA in the nucleus comes from both parents.

In the future, researchers will pay close attention to cases of human
heterogeneity. What's certain is that our view of genetic heredity has expanded so
much that we can't tell where the discovery can take us. From new gene therapy to
the evolution of our species, we don't know how far that can go.
Link:
https://medium.com/@wyzandrea/mitochondrial-dna-sometimes-comes-from-fathe
rs-46e9db155b34