We're All Mutants: The Average Human Has 60 New Genetic Mutations

Natalie Wolchover, Life's Little Mysteries Staff Writer

When parents pass their genes down to their children, an average of 60 errors are introduced to the genetic code in the process, according to a new study. Any of those five dozen mutations could be the source of major differences in a person's appearance or behavior as compared to his or her parents — and altogether, the mistakes are the driving force of evolution.

Sixty mutations may sound like a lot, but according to the international team of geneticists behind the new research, it is actually fewer than expected. "We had previously estimated that parents would contribute an average of 100 to 200 mistakes to their child," Philip Awadella, a geneticist at the University of Montreal who co-led the project, said in a press release. "Our genetic study, the first of its kind, shows that actually much fewer mistakes, or mutations, are made."

That means human evolution happens more slowly than they previously thought.

The researchers analyzed the complete genetic sequences of two families that had previously been collected as part of the 1,000 Genomes Project. They looked for new mutations present in the children's DNA that were absent from their parents' genomes. "Like very small needles in a very large haystack," Awadalla said, there was only one new mutation in every 100 million letters of DNA. [Read:How to Speak Genetics]

The number of mutations that came from each parent was drastically different in the two different families. In one family, 92 percent of the mutations in the child's genes derived from the father, whereas in the other family, 64 percent came from the mother.

"This was a surprise: many people expected that in all families, most mutations would come from the father, due to the additional number of times that the genome needs to be copied to make a sperm, as opposed to an egg," said Matt Hurles, of the Wellcome Trust Sanger Institute in the U.K. More work must be done to explain the disparity.

The new techniques and algorithms developed for the research, which is detailed in the latest issue of Nature Genetics, can be used in the future to answer additional questions. For example, how does a parent's age affect the number of mutations passed to his or her offspring? How do their various environmental exposures impact mutation rates?

Geneticists will find out by comparing the number of new mutations in children born to parents of differing ages and life experiences.

This article was provided by Life's Little Mysteries, a sister site to LiveScience. Follow Natalie Wolchover on Twitter @nattyover.

• Is Bad Handwriting Genetic? 
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http://news.yahoo.com/s/livescience/20110616/sc_livescience/wereallmutantstheaveragehumanhas60newgeneticmutations

Lifestyle You Lead Today May Affect Generations to Come

Dennis Thompson, HealthDay Reporter

WEDNESDAY, June 8 (HealthDay News) -- A new twist has been thrown into the classic debate of "nature versus nurture" through the budding field of epigenetics, which has found that nurture can alter the genetic nature of both an individual and the person's descendents.

Epigenetics researchers investigate the ways that environmental factors -- pollution, emotional stress, physical trauma -- can affect the way people's genetic blueprint is expressed through their physical and emotional development.

"Decades ago, we looked at genes as being the hard-wired plan for how the body develops and functions," said Dr. Steven Dowshen, chief medical editor of KidsHealth at the Nemours Center for Children's Health Media and a pediatric endocrinologist with the Alfred I. duPont Hospital for Children in Wilmington, Del. "That still is the case. However, we didn't understand until we knew more about this concept of epigenetics how environmental factors can change how those genes work."

Doctors studying epigenetics also have found evidence that a person's current environment can affect the health of their progeny, with today's events echoing decades down the family tree.

The word "epigenetics" provides a clue to the concept, as the Greek prefix "epi" means "over" or "above." Researchers have found that environmental factors essentially can flip an on or off switch in a person's genetics, affecting not only that person's development but also how genetics are transmitted in the person's eggs or sperm.

"Epigenetic mechanisms don't alter the actual DNA structure, but they do alter the DNA molecule in a way that modifies the amount of biologic information that will be transmitted by the gene," said Rachel Yehuda, a professor of psychiatry and neurobiology and director of the traumatic stress studies division at the Mount Sinai School of Medicine in New York City. "Imagine if you're listening to beautiful music and somebody mutes it. The music might still be playing, but it won't be heard. Or you can amplify that music."

Evidence of an epigenetic influence on human health and development include studies that found:

l   Hormonal differences in children born to mothers who had suffered extreme emotional and physical trauma. The differences make the children more susceptible to such mood disorders as anxiety and depression. The changes have been observed in second- and third-generation offspring of Holocaust survivors, as well as in the children of women who were pregnant on Sept. 11, 2001, and were evacuated from the World Trade Center, Yehuda said.

l   Extended longevity in people whose grandfathers suffered from malnourishment or starvation as children. This came from a landmark Swedish study that found that children raised in years when the harvest was bad produced grandchildren who lived longer than children who had plentiful food during their formative years, Dowshen said.

l   An effect on offspring from such behaviors as smoking and overeating. Dowshen said that such behaviors can predispose a person's children to systemic diseases, including diabetes and obesity.

Epigenetic effects aren't necessarily generational, however. There is evidence that trauma and stress may affect a person's psychological health by fiddling with the genetics that regulate body chemicals, Yehuda said.

"We think that epigenetics may be very informative in helping us understand why environmental events like trauma may be so transformative," she said. "When people undergo watershed life events, they say they are changed by them. What does that mean? This might help explain that."

The medical benefits of an epigenetic view of health and human development are not some pie-in-the-sky notion. Doctors already are putting this view of genetics to work in the treatment of patients.

"We're probably using epigenetics already in, for example, giving folic acid to pregnant women to prevent neural tube defects that cause spina bifida," Dowshen said. Folic acid influences the way a woman's DNA is expressed in her offspring, reducing the chances of the baby developing the devastating birth defect.

Epigenetics also have led doctors to encourage pregnant women to eat well, avoid alcohol and smoking, and eliminate as much stress as possible in their environment, he added.

In the future, findings from epigenetic studies could uncover ways to treat depression, cancer and much more by manipulating a person's genetics, Dowshen and Yehuda said.

"When treating depression, instead of treating the chemicals that flow through our neurons using antidepressants, we might be able to tackle more immediate causes for these chemical imbalances," Yehuda said.

People with a family history of cancer may be able to avoid developing the disease through epigenetic therapies that inhibit the expression of cancer-causing genes, Dowshen said. Manipulation of those genes might even lead to a cure for cancer one day.

In the meantime, epigenetics experts say, people today should realize that the lifestyle they lead will affect not only their own health but will probably have an impact on their children and grandchildren as well.

"Environmental factors like eating a healthy diet and physical activity and exercise are very likely influencing not just that individual but several generations emanating from them," Dowshen said. "It's likely that leading a healthy lifestyle will turn out to be understood to have some very direct effects on subsequent generations."

More information

The Nemours Foundation has more on epigenetics.

http://news.yahoo.com/s/hsn/20110608/hl_hsn/lifestyleyouleadtodaymayaffectgenerationstocome

Study: Genes Influence Who Your Friends Are

Stephanie Pappas, LiveScience Senior Writer

You may have more in common with your friends than a shared sense of humor or a penchant for the same bar. A new study finds that friends often resemble each other at the level of their genomes - though certain genes may influence people to bond with others who aren't like them.

Research has shown that birds of a feather do, in fact, flock together most of the time: People tend to become friends with people similar to themselves. Studies have also shown that that people's friendship styles - the number of friends they have and how central they are in their social network - are influenced by genetics.

These findings raised the question of whether genes play a role in whom we choose to become friends with, said James Fowler, a professor of political science and medical genetics at the University of California, San Diego. Fowler and his co-author Nicholas Christakis explored these theories in their book "Connected: The Surprising Power of Our Social Networks and How They Shape Our Lives" (Little Brown, 2009).

"We hypothesize that we're not just similar to our friends socially or behaviorally," Fowler. "We may also be similar to them biologically or genetically."

Friends and Genes

To find out if that theory holds water, Fowler and his colleagues culled data from two large, long-running studies, the National Longitudinal Study of Adolescent Health and the Framingham Heart Study. Both studies collect genetic information as well as data on who knows whom through friendship, marriage and other relationships.

The researchers tested the friendship pairs from the studies for six genes known to influence human behavior. Most of the genes tested influence the neurotransmitters serotonin or dopamine. (Serotonin is associated with mood and happiness, while dopamine plays many roles in motivation, reward-seeking behavior, learning and attention.)

People who live near each other tend to have similar genomes simply because they're more likely to have shared an ancestry. To control for this "population stratification," Fowler and his colleagues controlled for ethnicity and included siblings of the subjects in the analysis. Including data from siblings allowed the researchers to see how much of the correlation between genes and friendship was due to population stratification and how much was a real effect.

Of the six genes tested, two clustered among friends in unexpected ways. The first, the DRD2 gene, codes for a dopamine receptor in the brain, and some variants have been associated with alcoholism in previous studies. People with similar variants of DRD2 tend to stick together, the researchers report this week in the journal Proceedings of the National Academy of Sciences.

A second gene, the CYP2A6 gene, had the opposite effect. People with similar variants of the CYP2A6 gene tended to befriend people with different CYP2A6 gene variants. Little is known about this gene, the researchers wrote. It's responsible for a protein that metabolizes several compounds, including nicotine. One earlier study associated the gene with personalities that are open to new ideas.

A sea of genes

While the CYP2A6 gene effect is somewhat mysterious, it's not hard to imagine that a person with alcoholic tendencies might be drawn to people and places that non-drinkers would avoid, Fowler said. Researchers can't yet say if people's genes influence their friendships mostly by pushing people into environments with like-minded (and like-genomed) individuals, or if people are choosing pals based on genetically influenced personality traits. The finding that opposite CYP2A6 variants attract suggests, however, that some individual choice is involved, Fowler said.

"With the negatively correlated gene, we can rule out the possibility that you and I have been drawn to the same environment because we have the same genotype, because we don't have the same genotype," Fowler said.

The findings are a "first step," Fowler said. He and his colleagues hope to repeat the study with whole-genome scans to test all 25,000 genes humans are estimated to have instead of just the six the researchers initially tested.

If the results hold (or if more influential genes are discovered), they could add another wrinkle to the mystery of gene-environment interaction. If genes influence a person's social environment, that social environment could, in turn, influence the person's behavior: Imagine an alcoholic who befriends other alcoholics. Hanging out in an alcoholic crowd could encourage the person to drink more.

But people may also choose friends under the subtle influence of evolution, Fowler said. Previous research has found that people tend to choose spouses with different immune-system genetics than their own, perhaps to increase their protection against contagious diseases (if you can't fight off a bug, you want to be sure your partner won't get ill and transmit that same bug to you). Perhaps the CYP2A6 gene, while not linked to the immune system, plays a similar protective role.

"We live in a sea of the genes of others," Fowler said. "We are not just influenced by our own genes... We think that we are going to find more and more biological processes underlying the social networks that we live in."

• 7 Personality Traits That Are Bad For You 
• Brains Hard-Wired to Connect With Friends 
• 10 Things You Didn't Know About You 

http://news.yahoo.com/s/livescience/20110118/sc_livescience/studygenesinfluencewhoyourfriendsare

'Impulsive' Gene Identified in Finnish Men

Stephanie Pappas, LiveScience Senior Writer
Being impulsive at the shopping mall is one thing, but the personality trait at the extreme is linked to violence and criminal behavior. Now scientists have found a gene mutation behind such impulsive behavior.

The gene mutation affects the action of the neurotransmitter serotonin, a hormone known to be related to self-control, according to the researchers.

The mutation, which is found only in Finnish populations, shows up three times more often in violent criminal offenders than in psychologically healthy Finns, the study found. However, the researchers caution that the mutation itself does not cause impulsivity, but may play a role along with factors like gender, alcohol consumption and stress.

"We've known that impulsivity is strongly influenced genetically, but here's a severe genetic variant that does contribute to it," study author David Goldman, a geneticist at the National Institute on Alcohol Abuse and Alcoholism (NIAAA), told LiveScience.

Impulsive genes

Earlier studies have found that low serotonin levels are associated with impulsive behavior. Research also has suggested a heritable component to impulsive behavior and to disorders involving impulsivity, such as attention deficit hyperactivity disorder (ADHD).

In the current study, researchers recruited 96 Finnish men who were in jail for violent offenses and 96 psychologically healthy Finnish men who were not incarcerated. Finns were chosen for the study, because the Finnish population is more isolated than other populations and therefore hosts a less-diverse array of genetic mutations.

Goldman and his colleagues analyzed each man's genome, focusing on 14 genes known to be related to the function of the neurotransmitters dopamine and serotonin. They found a mutation on a gene called HTR2B was associated with impulsive, violent behavior. HTR2B contains the instructions for a serotonin receptor found all over the brain, especially in the frontal lobe, the seat of impulse control. The mutation in HTR2B is a misplaced "stop codon," or genetic code that halts the transcription of a gene into a functional product. The stop codon prevents the expression of the serotonin receptor.

History of violence

Seventeen of the 96 inmates had the gene mutation, a rate three times that of the non-incarcerated participants. On average, the prisoners had committed five violent crimes apiece, 94 percent of which occurred under the influence of alcohol. The crimes were not premeditated and were usually an overreaction to a minor incident, the researchers report. The study also revealed that 70 percent of participants with the mutation had displayed suicidal behavior.

To better understand the role of the gene, the researchers bred mice with the same mutation. They found that mutated mice were more likely to show impulsive behaviors when exposed to new objects or environments than were regular mice. The mice with the mutation also had higher testosterone levels, a trait they shared with human men with the same mutation.

Genes aren't destiny, the researchers were quick to warn.

"The [mutant] allele can be regarded as one determinant of behavioral variation," the researchers wrote. "However, the presence of [the mutation] was not in itself sufficient: male sex, testosterone level, the decision to drink alcohol, and probably other factors such as stress exposure, all have important roles." (An allele is a gene variant.)

In other words, Goldman said, the gene isn't sufficient to turn someone to a life of crime.

"What we've extrapolated is that over 100,000 Finns carry this variant," he said. "Most of them will never commit any highly impulsive act, much less a criminal act."

The fact that the mutation is only present in Finns is a reminder of the genetic diversity of complex traits like psychiatric disorders or propensity toward impulsivity, University of California, San Diego psychiatrist John Kelsoe wrote in a News & Views article accompanying the study.

"But although this specific mutation is absent in non-Finnish populations, different mutations in the HTR2B gene might operate in other populations," Kelsoe, who was not involved in the study, wrote.

• Understanding the 10 Most Destructive Human Behaviors

• 10 Easy Paths to Self-Destruction

• Fight, Fight, Fight: The History of Human Aggression

http://news.yahoo.com/s/livescience/20101223/sc_livescience/impulsivegeneidentifiedinfinnishmen

'Liberal gene' discovered by scientists

People with left wing views may have their political opinions controlled by a "liberal gene", according to scientists.

Telegraph.co.uk, 10/28/10

The research suggests that some people have an inherent bias against conservative thinking, that is independent of their education or upbringing.

The effect is caused by a neurotransmitter in the brain called DRD4 which could be stimulated by the novelty value of left of centre opinions, say US researchers.

In people who are naturally outgoing, the feature encourages them to seek out companions with unconventional views as they grow up.

This in turn means they tend to form less conventional political viewpoints as adults, according to the study by the University of California and Harvard.

The research, based on 2,000 Americans, is published in the Journal of Politics.

It found those with a strain of the DRD4 gene seek out "novelty" - such as people and lifestyles which are different to the ones they are used to.

This leads them to have more liberal political opinions, it found.

The person's age, ethnicity, gender or culture appeared to make no difference - it was the gene which counts.

DRD4 is controlled by dopamine which affects the way the brain deals with emotions, pleasure and pain and can therefore influence personality traits.

UC Professor James Fowler said: "It is the crucial interaction of two factors - the genetic predisposition and the environmental condition of having many friends in adolescence - that is associated with being more liberal.

"These findings suggest that political affiliation is not based solely on the kind of social environment people experience."

http://www.telegraph.co.uk/science/science-news/8093089/Liberal-gene-discovered-by-scientists.html