Category Archives: Human Genetics

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Scientists are still unraveling natures secret olfactory signals

Since pheromones were first defined in 1959, scientists have found many examples of pheromonal communication. Credit: Thinkstock

Strange as it may sound, some scientists suspect that the humble armpit could be sending all kinds of signals from casual flirtation to sounding the alarm. Thats because the bodys secretions, some stinky and others below the threshold your nose can detect, may be rife with chemical messages called pheromones. Yet despite half a century of research into these subtle cues, we have yet to find direct evidence of their existence in humans. What Are Pheromones? Humans and other animals have an olfactory system designed to detect and discriminate between thousands of chemical compounds. For more than 50 years, scientists have been aware of the fact that certain insects and animals can release chemical compoundsoften as oils or sweatand that other creatures can detect and respond to these compounds, which allows for a form of silent, purely chemical communication.

Although the exact definition has been debated and redefined several times, pheromones are generally recognized as single or small sets of compounds that transmit signals between organisms of the same species. They are typically just one part of the larger potpourri of odorants emitted from an insect or animal, and some pheromones do not have a discernable scent.

Since pheromones were first defined in 1959, scientists have found many examples of pheromonal communication. The most striking of these signals elicits an immediate behavioral response. For example, the female silk moth releases a trail of the molecule bombykol, which unerringly draws males from the moment they encounter it. Slower-acting pheromones can affect the recipients reproductive physiology, as when the alpha-farnesene molecule in male mouse urine accelerates puberty in young female mice.

Some researchers have proposed a third group of pheromones called signalers that simply transmit information such as an individuals social status or health. Mice can select appropriate mates based on odor cues, deriving information in part from unique proteins associated with a mouses genetics. The Trouble with Humans

So far, scientists have had some success in demonstrating that exposure to body odor can elicit responses in other humans. As in rodent research, human sweat and secretions can affect the reproductive readiness of other humans. Since the 1970s researchers have observed changes in a womans menstrual cycle when she is exposed to the sweat of other women. In 2011 a Florida State University group demonstrated that the scent of ovulating women could cause testosterone levels to increase in men.

But there is no evidence of a consistent and strong behavioral response to any human-produced chemical cue. Maybe once upon a time we could react more viscerally, says chemist George Preti of the Monell Chemical Senses Center. Today, however, our reactions seem to be much subtlerand harder to detectthan those of a silk moth. This subtlety has led researchers to propose another kind of chemical messenger, known as a modulator pheromone, that affects the mood or mental state of the recipient. In an example of this type, researchers at Stony Brook University found in 2009 that sniffing the sweat of first-time parachute jumpers could increase a persons ability to discriminate between ambiguous emotional expressions. The implication is that chemicals in the jumpers sweat might constitute an alarm signal, which puts the recipient on high alert and makes them more attentive to details.

Yet to demonstrate definitively that pheromones are at work, researchers need to point to the molecules responsible, which they have not yet done. To date, scientists have collected evidence for possible pheromone effects but have not definitively identified a single human pheromone. A Signature Scent

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Are Human Pheromones Real?

Beings Less and Less Dependent on Parents to Exist Washington, D.C., April 10, 2014 (Zenit.org) Denise Hunnell, MD | 454 hits

Both the 1932 novel Brave New World by Aldous Huxley and the 1997 science fiction movie Gattaca are classified as dystopias because they depict societies riddled with misery, tragedy, and a dehumanizing culture. Both attribute this decline in civilization to manipulations of human genetics and perversions of human reproduction. In Brave New World the traditional family structure has completely disintegrated and children are manufactured in hatcheries through in vitro fertilization (IVF) and gestation. In Gattaca, human beings are enhanced through genetic alterations, and those who do not have their DNA modified are seen as second-class citizens.

It is curious that genetically modified humans can be clearly seen as dangerous and undesirable in fiction but are celebrated as great achievements in current biomedical sciences. In the name of progress we are steadily marching forward to separate human procreation from human relationships and make it a laboratory procedure.

The floodgates of artificial reproductive technology were opened in Great Britain on July 25, 1978, with the birth of Louise Brown, the first test tube baby. In the ensuing years the use of IVF has fueled the growth of the multi-billion dollar fertility industry. The growing demand for ova to produce children for infertile couples has led to the widespread exploitation of young women as egg donors. Similar exploitation of poor women in countries like India has occurred as couples seek both egg donors to help conceive a child and a surrogate mother to gestate the child. Both women and children are dehumanized as human reproduction is commercialized.

The development of pre-implantation genetic diagnosis (PGD) pushed artificial reproductive technology to a new level of genetic manipulation. It is no longer sufficient to conceive a child, but that child must now be defect free. Embryos are conceived through IVF, but before they are implanted in the uterus, their DNA is screened for chromosomal abnormalities. Embryos found to have undesirable genetics are discarded as medical waste with no regard for their humanity. These nascent human beings may be destroyed because they have chromosomal patterns linked to diseases like Down syndrome or Trisomy 18, or they may have the gene linked to familial cancers, or they may just be the wrong sex. Sex-selection abortions and sex-selection of embryos for implantation have led to serious gender imbalances in countries like China and India where sons are highly preferred over daughters.

If one can select against undesirable traits, the next logical leap is to choose embryos that have desirable features. With the help of a billion dollar investment from the Chinese government, the Chinese firm B.G.I. is working to make selecting the most intelligent embryo a viable option. It is not unreasonable to think that the selection for other traits such as physical attractiveness or athletic ability cannot be far behind.

The idea of building the perfect child is part of the philosophical principle of procreative beneficence. The term was coined by Oxford professor Julian Savulescu, and refers to a form of utilitarianism that asserts parents have a moral obligation to produce the best child possible. The utilitarian foundation of his reasoning only values those who produce a material benefit to others. The sick, the weak, and the disabled drain resources and are therefore disposable. Professor Savulescu freely admits this amounts to eugenics. He justifies it as providing the greatest good to most people. However, the good that he seeks only benefits the strong and powerful, and is obtained at the expense of the weak and vulnerable.

Current reproductive technology requires fully formed gametes, ova and sperm, to produce human embryos. What if that requirement was removed? The next big leap in artificial reproductive technology is in vitro gametogenesis. Adult or embryonic stem cells are manipulated in the laboratory to function as gametes. This removes the need for both male and female donors. Ova and sperm can be produced from stem cells from either a man or a woman. This would allow same-sex couples to have children that are genetically related to both partners. Theoretically, in vitro gametogenesis could allow a single person to use his own cells to produce two gametes and have a child with only one biological parent.

In a 2013 article in the Journal of Medical Ethics,Dr. Robert Sparrow of Monach University in Australia invokes Savulescus procreative beneficence and outlines the potential uses of in vitro gametogenesis. He suggests that this technology would allow the breeding of better humans. Embryos could be produced and screened for desirable traits. Instead of implanting these embryos for gestation, their stem cells could be harvested and used to make more gametes. These would be used to make another generation of embryos that are again screened and selected. This process could be repeated again and again until the desired refinement of the genome is achieved. The embryo who is ultimately selected for full gestation may actually be several generations removed from his last relative who was actually born. Dr. Sparrow points out that the use of in vitro gametogenesis could shorten the time span between successive generations to a matter of months instead of a matter of decades.

In vitro gametogenesis does not require naturally formed gametes, but it does require naturally formed DNA. Dr. Jef Boeke and his research team, working at both Johns Hopkins University in Baltimore and New York University, are working to remove even that constraint. They have successfully constructed the first synthetic yeast chromosome. The yeast has a cell structure very similar to humans, so this work is seen as the first steps towards producing a completely synthetic human genome. While the research is in its infancy, the ultimate goal is mind-boggling. Children that have no biological parents could be produced from gametes made with synthetic DNA. Their DNA would be designed in the laboratory to meet the specifications of whoever is commissioning their creation.

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Artificial Reproductive Technology: Constructing a Dystopia

You probably wouldn't guess it, but some of the world's foremost genetics research is happening right here in South Dakota. Last Fall we introduced you to the rare partnership that Avera has with genetics research in the Netherlands. Now we'll give you a closer look at the research being done.

At the Avera Institute for Human Genetics, scientists continue to dive into the deep end of the gene pool.

"Things just continue to amaze me on how we progress and the findings we find!" Said Dr. Gareth Davies, a molecular geneticist and the scientific director for the institute.

Thanks to the collaboration with the Netherlands Twin Registry, researchers here in Sioux Falls have access to more than 40,000 DNA samples to help further their study.

"They (the samples) are stored with their co-twin and also with their parents; so each row we have two twins and then mom and dad." Said Dr. Davies.

Studying twins gives scientists a better understanding on the role genetics play in behaviors and disease because identical twins share the same DNA; that is until you look very closely.

"What we find is that if you look at copy number variations not all identical twins need to be completely identical." Said Dr. Dorret Boomsma of Vrije University in Amsterdam and pioneer of the Netherlands Twin Registry.

A copy number variation or CNV is when a chromosome that makes up a gene is either added or deleted. Take for example if I had a twin. Our DNA is identical but for one of my genes, the chromosome makeup is A-B-C-D and for my twin that same gene makeup is A-B-C-C-D. That extra "C" is the only difference, but it could be what causes different behavior traits or disease susceptibility between us two. However, just having a gene linked to disease doesn't put you at risk.

"We have known that they can be switched on and switched off but we didn't realize how important the environment was, the environment outside the cell, and how it could affect the structure of the DNA and alter how those genes are switched off and on." Said Dr. Davies.

Research continues to support the thought that genetics may load the gun, but it's the environment that pulls the trigger.

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Avera Medical Minute AMcK: Researching the human genome

Wellcome Trust Centre for Human Genetics
The WTCHG is a research institute of the Nuffield Department of Medicine at the University of Oxford, funded by the University, the Wellcome Trust and numero...

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Wellcome Trust Centre for Human Genetics - Video

Human Genetics Biology Project
Type 1 Diabetes documentary.

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Human Genetics Biology Project - Video

By ASHLEY CHU

With a five-year, $10 million grant from the National Institute of Child Health and Human Development, a Center for Reproductive Genetics will be established on both Cornells Ithaca and Weill Cornell Medical School campuses.

The CRG is aimed at understanding the genetic basis for processes that give rise to healthy gametes for reproduction, said Prof. Paula Cohen, biomedical sciences, who is director of the CRG. If you dont have healthy eggs and sperm, then this can lead to all sorts of issues such as birth defects, miscarriages, preterm delivery and infertility.

This grant which the University announced it had received on April 1 marks a significant milestone for groups researching reproductive genetics, according to Cohen.

This is the first time that a number of groups are being funded collectively to ask the same questions and, as such, this is likely to bring rapid advances in our knowledge, Cohen said. In science, so often we work in isolated bubbles, but this center grant, which encompasses five different investigators in four different projects, is likely to lead to bigger and quicker advances.

The center aims to address these issues at the basic research level in a joint effort between the two campuses, which Cohen describes as the bench-to-bedside approach.

Given that the CRG is based on both the Ithaca and Weill Cornell campuses, we hope to translate our findings from the lab into the clinic to help infertile couples and to understand how birth defects arise in humans, Cohen said.

The CRGs research focus is to understand how healthy gametes are produced, but more specifically, how the defects that arise during gametogenesis are produced.

This grant will enable cutting-edge research, using the latest technological advances and discoveries, to better understand fundamental processes in mammalian spermatogenesis. Jen Grenier

Given how important healthy eggs and sperm are for sexual reproduction and how conserved the genetic processes are that give rise to these cells, its surprising to find that human gametogenesis the process that gives rise to sperm and eggs is extremely error prone, Cohen said. In fact, between 40 and 60 percent of human eggs contain the wrong complement or number of chromosomes, and this situation can lead to spontaneous miscarriages or birth defects such as Down syndrome and Klinefelter syndrome.

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Center for Reproductive Genetics Established With $10 Million Grant

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As a teenager in Germany, Steve Horvath, his identical twin Markus and their friend Jrg Zimmermann formed 'the Gilgamesh project', which involved regular meetings where the three discussed mathematics, physics and philosophy. The inspiration for the name, Horvath says, was the ancient Sumerian epic in which a king of Uruk searches for a plant that can restore youth. Fittingly, talk at the meetings often turned to ideas for how science might extend lifespan.

At their final meeting in 1989, the trio made a solemn pact: to dedicate their careers to pursuing science that could prolong healthy human life. Jrg set his eye on computer science and artificial intelligence, Markus on biochemistry and genetics, and Steve says that he planned to use mathematical modelling and gene networks to understand how to extend life. Jrg did end up working in artificial intelligence, as a computer scientist at the University of Bonn in Germany, but Markus fell off the wagon, his brother says, and became a psychiatrist.

Steve, now a human geneticist and biostatistician at the University of California, Los Angeles (UCLA), says that he finally feels poised to make good on the promise. Through a hard-fought project that involved years of solo work, multiple rejections by editors and reviewers and battling through the loss of a child, he has gathered and analysed data on more than 13,000 human tissue samples1. The result is the a cellular biological clock that has impressed researchers with its accuracy, how easy it is to read and the fact that it ticks at the same rate in many parts of the body with some intriguing exceptions that might provide clues to the nature of ageing and its maladies.

Horvath's clock emerges from epigenetics, the study of chemical and structural modifications made to the genome that do not alter the DNA sequence but that are passed along as cells divide and can influence how genes are expressed. As cells age, the pattern of epigenetic alterations shifts, and some of the changes seem to mark time. To determine a person's age, Horvath explores data for hundreds of far-flung positions on DNA from a sample of cells and notes how often those positions are methylated that is, have a methyl group attached.

He has discovered an algorithm, based on the methylation status of a set of these genomic positions, that provides a remarkably accurate age estimate not of the cells, but of the person the cells inhabit. White blood cells, for example, which may be just a few days or weeks old, will carry the signature of the 50-year-old donor they came from, plus or minus a few years. The same is true for DNA extracted from a cheek swab, the brain, the colon and numerous other organs. This sets the method apart from tests that rely on biomarkers of age that work in only one or two tissues, including the gold-standard dating procedure, aspartic acid racemization, which analyses proteins that are locked away for a lifetime in tooth or bone.

I wanted to develop a method that would work in many or most tissues. It was a very risky project, Horvath says. But now the gamble seems to be paying off. By the time his findings were finally published last year1, the clock's median error was 3.6 years, meaning that it could guess the age of half the donors to within 43 months for a broad selection of tissues. That accuracy improves to 2.7 years for saliva alone, 1.9 years for certain types of white blood cell and 1.5 years for the brain cortex. The clock shows stem cells removed from embryos to be extremely young and the brains of centenarians to be about 100.

Such tight correlations suggest there is something seemingly immutable going on in cells, says Elizabeth Blackburn of the University of California, San Francisco, who won a Nobel prize for her research on telomeres caps on the ends of chromosomes that shorten with age. It could be a clue to undiscovered biology, she suggests. And there may be medical implications in cases in which epigenetic estimates do not match a person's birth certificate.

In the months since Horvath's paper appeared, other researchers have replicated and extended the results. The study has stirred up excitement about potential applications, but also debate about the underlying biology at work.

It's something new, says Peter Visscher, chair of quantitative genetics at the University of Queensland in Australia. If he's right that there is something like an inherently epigenetic clock at work in ageing, that is very interesting. It must be important.

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Biomarkers and ageing: The clock-watcher

A new genome analysis method has confirmed that Neanderthals interbred with ancestors of Eurasians, a new study reports.

The findings, published in the April 2014 issue of the journal Genetics, explains how Neanderthals most likely interbred with modern humans after they migrated out of Africa. The new technique ruled out the other popular theory that humans who left Africa evolved from the same ancestral subpopulation where Neanderthals evolved from.

"Our approach can distinguish between two subtly different scenarios that could explain the genetic similarities shared by Neanderthals and modern humans from Europe and Asia," Konrad Lohse, study co-author and population geneticist at the University of Edinburgh in Scotland,said in a statement.

The method differs from others in that it used one genome from Neanderthals, Eurasians, Africans and chimpanzees rather than comparing genomes from many modern humans. The same method will have other uses to, especially in studies of suspected interbreeding where limited samples are available.

We did a bunch of math to compute the likelihood of two different scenarios," Laurent Frantz, study co-author and evolutionary biologist at Wageningen University in the Netherlands,told The Verge. "We were able to do that by dividing the genome in small blocks of equal lengths from which we inferred genealogy."

Scientists developed the method after studying the history of insect populations in Europe and rare pig species in Southeast Asia.

"This work is important because it closes a hole in the argument about whether Neanderthals interbred with humans. And the method can be applied to understanding the evolutionary history of other organisms, including endangered species," Mark Johnston, editor-in-chief of the journal Genetics, said.

Frantz thinks the study may also change the way evolution is perceived.

"There have been a lot of arguments about what happened to these species," he said. "Some think that we outcompeted [other hominins] or that they were killed by humans, but now we can see that it's not that simple."

Neanderthals may have been recruited into certain human populations that they may have been in contact with on a daily basis. This goes against a commonly held perception of evolution where species struggled to survive.

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Neanderthals Interbred With Humans? New Method Closes A Hole In Evolution Argument

Some patients with a suspected genetic disorder will go on what medical professionals call a diagnostic odyssey to find the cause of their symptoms.

A sample is run through the HiSeq 2000, a high-throughput sequencing system in the DNA lab at the University of Iowa Eckstein Medical Research Building in Iowa City. The green dots on the screen show a cluster of the fragment being sequenced. The lab also uses a HiSeq 2500, which can complete sequencing in 27 hours to the HiSeq 2000's 12 days. The Iowa Institute of Human Genetics at the University of Iowa is now offering whole exome sequencing, which is among several initiatives the institute is pursuing to further personalize medicine for patients. (Liz Martin/The Gazette-KCRG)

But those explorations, on occasion, can come up empty, frustrating patients and prompting health care providers to seek outside expertise.

Last month, the Iowa Institute of Human Genetics at the University of Iowa began offering such expertise through whole exome sequencing.

The genetic test, which analyzes a portion of about 20,000 genes in the human genome in hopes of helping practitioners diagnose and treat a patient, is among several initiatives the institute is pursuing to further personalize medicine for patients in Iowa and across the country.

The research we do here is to develop new tests to bring precision medicine to the state, said Colleen Campbell, assistant director of the Iowa Institute of Human Genetics and associate with the UI Department of Otolaryngology.

Researchers with the institute also are conducting tests around secondary findings from exome sequencing the discovery of variants in genes unrelated to a patients primary condition and how a persons genes interact with prescribed medication, including pain medication.

The technology is new, but officials with the Iowa institute said genetic sequencing one day could become so widely used that every infant will have it done as part of the standard newborn screen. Then, as a child grows, practitioners will be able to use the information to determine what type of pain medication to prescribe and at what level, for example.

Our focus is to bring innovation to the state, Campbell said. We want patients to be more informed when they go to the doctor and are offered these new tests. And we want to be able to offer this as a tool to doctors.

The Iowa Institute of Human Genetics is among only a dozen or so institutions nationally that offer whole exome sequencing to physicians wanting to order the test on behalf of a patient.

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University of Iowa hopes to use sequencing to better diagnose and treat patients

2. Inheritance pattern in human
For more information, log on to- http://shomusbiology.weebly.com/ This video explains about different types of inheritance pattern of human diseases like dom...

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