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Post by Admin on Nov 29, 2018 18:12:06 GMT
The research, published in the Proceedings of the National Academy of Sciences, showed conclusively that, in three unrelated families, mitochondria from the father’s sperm had been passed to the children over several generations. Overturning scientific understanding about this fundamental truth, opens the possibility for better treatment of mitochondrial disorders, which blight many families with devastating disease. Most of a cell’s DNA is contained in its nucleus but mitochondria sit separately inside the cell and have their own DNA. This is because mitochondria are thought to have started as separate organisms, which entered early cells about 1.45 billion years ago and never left. They reproduce themselves and move from one generation to another by ‘hitching a lift’ in the egg. During fertilization, the father’s sperm transfers his DNA into an egg, but few or none of the sperm’s mitochondria get in. If any do, then there are mechanisms designed to destroy them. The new research found that, in a small number of families, the mitochondria from the father that found its way into the egg were not destroyed, though we don’t yet know enough to say why. There was also some evidence this mitochondrial DNA from the father may have then been copied as the fertilized egg grew into an embryo even more than that from the mother. Significance The energy-producing organelle mitochondrion contains its own compact genome, which is separate from the nuclear genome. In nearly all mammals, this mitochondrial genome is inherited exclusively from the mother, and transmission of paternal mitochondria or mitochondrial DNA (mtDNA) has not been convincingly demonstrated in humans. In this paper, we have uncovered multiple instances of biparental inheritance of mtDNA spanning three unrelated multiple generation families, a result confirmed by independent sequencing across multiple unrelated laboratories with different methodologies. Surprisingly, this pattern of inheritance appears to be determined in an autosomal dominantlike manner. This paper profoundly alters a widespread belief about mitochondrial inheritance and potentially opens a novel field in mitochondrial medicine. Abstract Although there has been considerable debate about whether paternal mitochondrial DNA (mtDNA) transmission may coexist with maternal transmission of mtDNA, it is generally believed that mitochondria and mtDNA are exclusively maternally inherited in humans. Here, we identified three unrelated multigeneration families with a high level of mtDNA heteroplasmy (ranging from 24 to 76%) in a total of 17 individuals. Heteroplasmy of mtDNA was independently examined by high-depth whole mtDNA sequencing analysis in our research laboratory and in two Clinical Laboratory Improvement Amendments and College of American Pathologists-accredited laboratories using multiple approaches. A comprehensive exploration of mtDNA segregation in these families shows biparental mtDNA transmission with an autosomal dominantlike inheritance mode. Our results suggest that, although the central dogma of maternal inheritance of mtDNA remains valid, there are some exceptional cases where paternal mtDNA could be passed to the offspring. Elucidating the molecular mechanism for this unusual mode of inheritance will provide new insights into how mtDNA is passed on from parent to offspring and may even lead to the development of new avenues for the therapeutic treatment for pathogenic mtDNA transmission. PNAS published ahead of print November 26, 2018
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Post by Admin on Dec 2, 2018 18:10:01 GMT
THE SCIENTIFIC LANGUAGE OF GENETICS From chromosomes to DNA to dominant and recessive alleles, learning the language of genetics is equivalent to learning the subject itself. The following key terms are guaranteed to appear frequently in your study of all things genetic: Alleles: Alternative forms of a gene Autosomal chromosome: A nonsex chromosome Chromosome: A linear or circular strand composed of DNA that contains genes Diploid: An organism with two copies of each chromosome DNA: Deoxyribonucleic acid; the molecule that carries genetic information Dominant: A phenotype or allele that completely masks the presence of the other, recessive allele in the heterozygote Gene: The fundamental unit of heredity; a specific section of DNA within a chromosome Genotype: The genetic makeup of an individual; the allele(s) possessed at a given locus Heterozygote: An individual with two different alleles of a given gene or locus Homozygote: An individual with two identical alleles of a given gene or locus Locus: A specific location on a chromosome Phenotype: The physical characteristics of an individual Recessive: A phenotype or allele exhibited only when homozygous THE STRUCTURE OF THE CELL NUCLEUS AND ITS CHROMOSOMES If you could open the nucleus of a cell and peek inside, you’d find chromosomes — the strands of DNA where genes reside. This figure helps you see how all the parts of a chromosome relate to one another. THE STRUCTURE OF DNA DNA is made up of long chains of nucleotides. To make a complete DNA molecule, single nucleotides join to make chains that come together as matched pairs and form long double strands. Each nucleotide is comprised of the following: A five-sided (pentose) sugar called deoxyribose A phosphate One of four nitrogen-rich bases: adenine, guanine, cytosine, or thymine Nucleotides are joined together by phosphodiester bonds. Nucleotide chains are antiparallel and complementary.
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Post by Admin on Dec 9, 2018 18:06:26 GMT
A team of European and Moroccan scientists has found the fossil remains of five individuals they believe are the most ancient modern humans (Homo sapiens) ever found. In a remote area of Morocco called Jebel Irhoud, in what was once a cave, the team found a skull, bones, and teeth of five individuals who lived about 315,000 years ago. The scientists also found fairly sophisticated stone tools and charcoal, indicating the use of fire by this group. The researchers' claim is controversial, however, because anthropologists are still debating exactly what physical features distinguish modern humans from our more primitive ancestors. Archaic forms of humans — other, earlier species of Homo — emerged more than a million years ago. Exactly how and when our species — Homo sapiens — evolved is a mystery. Up to now, the oldest known bones widely recognized as Homo sapien were from people who lived in East Africa about 200,000 years ago. The new discovery in Morocco would push the date for the emergence of our species back another 100,000 years. Jean-Jacques Hublin directs the department of human evolution at Germany's Max Planck Institute for Evolutionary Anthropology. He led the team that found a skull, bones and stone tools. Fossil evidence points to an African origin of Homo sapiens from a group called either H. heidelbergensis or H. rhodesiensis. However, the exact place and time of emergence of H. sapiens remain obscure because the fossil record is scarce and the chronological age of many key specimens remains uncertain. In particular, it is unclear whether the present day ‘modern’ morphology rapidly emerged approximately 200 thousand years ago (ka) among earlier representatives of H. sapiens1 or evolved gradually over the last 400 thousand years2. Here we report newly discovered human fossils from Jebel Irhoud, Morocco, and interpret the affinities of the hominins from this site with other archaic and recent human groups. We identified a mosaic of features including facial, mandibular and dental morphology that aligns the Jebel Irhoud material with early or recent anatomically modern humans and more primitive neurocranial and endocranial morphology. In combination with an age of 315 ± 34 thousand years (as determined by thermoluminescence dating)3, this evidence makes Jebel Irhoud the oldest and richest African Middle Stone Age hominin site that documents early stages of the H. sapiens clade in which key features of modern morphology were established. Furthermore, it shows that the evolutionary processes behind the emergence of H. sapiens involved the whole African continent. An earlier origin for H. sapiens is further supported by an ancient-DNA study posted to the bioRxiv preprint server on 5 June. Researchers led by Mattias Jakobsson at Uppsala University in Sweden sequenced the genome of a boy who lived in South Africa around 2,000 years ago — only the second ancient genome from sub-Saharan Africa to be sequenced. They determined that his ancestors on the H. sapiens lineage split from those of some other present-day African populations more than 260,000 years ago. a, Principal component analysis (PCA) of the facial shape. EMH (black) and RMH (blue) are well separated from Neanderthals and archaic Middle Pleistocene hominins. This offers clues about the evolution of the H. sapiens lineage into today’s anatomically modern humans. Hublin suggests that anatomically modern humans may have acquired their characteristic faces before changes to the shape of their brains occurred. Moreover, the mix of features seen in the Jebel Irhoud remains and other H. sapiens-like fossils from elsewhere in Africa point to a diverse genesis for our species, and raises doubt about an exclusively East African origin. “What we think is before 300,000 years ago, there was a dispersal of our species — or at least the most primitive version of our species — throughout Africa,” Hublin says. Around this time, the Sahara was green and filled with lakes and rivers. Animals that roamed the East African savanna, including gazelles, wildebeest and lions, also lived near Jebel Irhoud, suggesting that these environments were once linked.
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Post by Admin on Dec 11, 2018 18:05:54 GMT
Little Foot In The Sterkfontein Cave 580 435 S 1 Little Foot was likely a 4-foot-3-inch-tall (130 centimeters) adult female and a vegetarian to boot, the researchers of the new studies found. In one bioRxiv study, published online Nov. 29, the researchers investigated how Little Foot likely moved. The researchers found that her arms were not as long as her legs, meaning she had similar proportions to those of modern humans. In fact, Little Foot is the oldest known hominin to have this feature, which suggests that she felt more at home walking on the ground than other, largely tree-dwelling Australopithecus species, Crompton told Nature. "My analysis of her skeleton shows that she, and the rest of the local population of her species at that time, were under active natural selection for an ability to walk efficiently, fully upright, on the ground over medium to long distances," Crompton told Live Science. The findings detailed in another bioRxiv study, published online Dec. 5, suggest that Little Foot sustained an arm injury early in life. Her forearms (the area between the wrist and the elbow) are not mirror images. Instead, the left forearm is more bowed than the right, the researchers wrote in the study. Perhaps, Little Foot fell onto a hyperextended, outstretched hand when she was a juvenile, they said. This type of deformation in forearm bones "is well-documented in modern human clinical studies, especially among children between the ages of 4 and 10 years who tumble from bicycles or suffer other common, relatively low-impact accidents," the researchers wrote. "Left untreated, such injuries impinge normal supination and pronation of the hand." However, Little Foot's injury healed long before she fell into the cave and died. "The fatal fall may have been during a struggle with a large monkey, as the skeleton of one was found very close to hers," Crompton told Live Science. In another study, scientists looked at how long ago Little Foot lived (the researchers suggest 3.67 million years ago), while the other study involved a comparison of her skull with those of other hominins. Future papers will detail findings about Little Foot's hands, teeth and inner ear, and the whole collection is slated to be published in a special edition of the Journal of Human Evolution, Crompton said. Given that Little Foot appears to be a newfound species (based, in part, on her teeth and hips), the researchers of the new studies named her Australopithecus prometheus. This name was given to a hominin skull fragment found in South Africa in 1948, but it fell by the wayside after researchers decided that the fragment likely belonged to an unusual A. africanus. But Lee Berger, an archaeologist at the University of the Witwatersrand who was not involved with the new research, said that if Little Foot is actually a newly identified species (something he's not sure of yet), then she deserves a new species name, not a recycled one that's not well-defined, Berger told Nature. But Crompton defended the name. After the A. africanus specimen was properly named, Clarke started using A. prometheus for other fragmentary bones found in the cave, Crompton told Live Science. The discovery of Little Foot is one of the greatest detective stories in the study of human evolution. Uniquely caught on film, Ron Clarke’s, fifteen year endeavor has produced the most complete skeleton ever found of one of our oldest ape-like ancestors. "It is bad practice, and against the International Code of Zoological Nomenclature, to create new names where a valid name already exists and no good argument for separation into a different species exists," Crompton said. "So, as Prof. Clarke did not have evidence that [Little Foot] was part of a different species than Australopithecus prometheus, and he had continued to use that name for some Sterkfontein fossils in the published scientific literature, it was entirely appropriate that he used the existing and valid name."
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Post by Admin on Dec 12, 2018 20:29:39 GMT
It was previously believed that red hair is inherited through two versions of the MC1R gene, one from your mom and one from your dad. However, the new research suggests that MC1R accounts for just 73 percent of heritability for red hair. Furthermore, the majority of people who carry two red-haired variants of the MC1R have brown hair or blonde hair. As published in the journal Nature Communications, the new research suggests that at least eight different genes are responsible for red hair. Things are a little more complex for people with blonde or brown locks, with almost 200 genes contributing to the pigmentation of their hair. The team also found that 12.7 percent of females in the UK have blonde hair and 5.2 percent have red hair, while 9.9 percent of males have blonde hair and 3.7 percent have red hair. The color of your hair, as well as the color of your skin and eyes, all depends on the amount and type of melanin produced by your melanocytes. The nature of your melanocytes, in turn, is determined by your genes. Along with other types of melanin, red hair usually contains high amounts of pheomelanin, which has a pinkish-red hue and is particularly concentrated in the lips, nipples, and genitals. On the other hand, dark hair usually contains more eumelanin. The job of MC1R is to turn red pigment into brown. When you have no working MC1R, you build up red pigment and have red hair. The researchers, from the University of Edinburgh in Scotland and Oxford University, reached their findings by sifting through the UK Biobank, a huge and unique genetic study of half a million people of European descent in Britain. That might sound limited at first, but the researchers argue the European population has some of the greatest natural variation of hair color in the world. Having two MC1R alleles is not a necessary condition for causing red hair, even though 92% of red-haired individuals are known to carry two MC1R alleles. 15% of people with two MC1R variants have blonde hair, while a variant in HERC2 is associated with a decreased probability of red hair. Probably one's hair color is determined by the interaction between these various pigmentation genes. For instance, Prince Harry's famous ginger hair is almost blonde. He is likely to have both MC1R and HERC2, which is associated with blue eyes and blonde hair, and the effect of MC1R is suppressed by HERC2.
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