BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: Twins

Genes: They are influential in more ways than one

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On October 29, 2020

In Student Post

The article entitled, “Your Friends May Be In Your Genes,” discusses the study Virginia Commonwealth University researchers led on the influence of genes on the choices that we make when developing social connections.  Researchers claim that as people mature, their genes become progressively more critical in how they choose their friend groups. The discoveries in the study reflect which people are most susceptible for substance use or externalizing behaviors in their lifetime, based on the company they keep.

Comprised of individuals who were part of the Virginia Twin Registry, the study looked into the role of genetic factors in decision making amongst men during their adolescence, using roughly 1,800 male twin pairs ranging from teenage years to early adulthood, and involved interviews used to help explain how social groups can influence deviant behaviors.  Specifically, the study showed that genes can impact how individuals select their peer groups, and that those groups affects one’s tendency to engage in antisocial behaviors. Because peers have a significant effect on promoting and/or discouraging deviant behaviors and also oftentimes provide substances for abuse, an individual’s social environment can play a critical role in his/her life choices.

As mentioned in the article, “Why Twin Studies,” Twin studies have long been used as a means to identify different illnesses and disorders because they allow researchers to determine the the various influences on certain traits.  If a trait is similar between individuals who have the same genes, like identical twins, but not so in fraternal twins, a case can be made for a genetic link.  If a trait is similar between fraternal twins, but not so in identical twins, then a case can be made for environmental impact.

In the article, “Its Nature and Nurture: How Our Genes and Our Friends Shape the Way We Live Our Lives,” further support is given to the link between genes, environment, and risky behaviors when it points out that more educated Americans are less likely to smoke.  Since educated people tend to surround themselves with like minded people who find smoking unacceptable, those who are socially connected in this way are not usually smokers.  This suggests that people who have genes linked to educational success are less likely to have genes linked to smoking and vice versa.

Genes are segments of DNA that contain the instructions for the production of proteins.  Cells contain organelles, called ribosomes that are responsible for producing proteins that control physical traits.  Genes provide the information for which amino acids need to be joined to build each protein.

Personally, I think genes are interesting not only because they control the traits that we posses, but also because they can be linked to who we chose to surround ourselves with. It is our social choices that can then determine behaviors we participate in.

 

 

CRISPR Scandal

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On January 14, 2019

In Student Post

Outrage is widespread in the scientific community, as one man’s choices may have ruined genome editing for everyone. With others calling his actions “premature,” “ethically problematic,” and “monstrous” Doctor He Jiankui remains confident in his File:He Jiankui at Second International Summit on Human Genome Editing.jpgactions. His action being creating the first genetically modified babies, twin girls born in November. “He had altered a gene in the embryos, before having them implanted in the mother’s womb, with the goal of making the babies resistant to infection with H.I.V..”

The chaos created by Dr. He’s actions are due to the fact that he failed to receive permission from an ethical board. He claims to have gotten the permission of the hospital, Shenzhen Harmonicare, but the hospital denies being involved. The hospital is even going as far as requesting a police investigation into the “fraudulent ethical review materials.” So without ethical approval, Dr. He seriously violated not only the Chinese government’s laws and regulations created by the Chinese Society for Cell Biology but also academic ethics and norms. He has risked opening the door to designer babies editing everything from eye color to I.Q and physical ability, while the CRISPR creators are attempting to limit the editing to cases of desperate unmet need where the cause cannot be prevented in any other way, unlike H.I.V. which is very easily avoidable in infants.

These twins, however, are the only known set of children to be produced from a trial of seven couples with an H.I.V. positive father and negative mother. Dr. He after deactivating the perfectly normal gene CCR₅ withFile:NHGRI-97218.jpg CRISPR-Cas9  implanted the embryos into their mothers. In deactivating the CCR₅, Dr. He made the girl’s resistant to H.I.V., but also made them more susceptible to West Nile virus and Japanese encephalitis. So while the babies were “born normally and healthy” according to Dr. He, Dr.Kiran Musunuru from the University of Pennsylvania said there was evidence of mosaicism in both twins embryos and Lulu’s placenta was also mosaic. Despite the mosaic placenta, both babies appear to be progressing well for now, but what will happen to them in the future is the unknown. While their health is positive for now, the effects will be felt in their progeny for generations to come in unknown ways as cells with CCR₅ and without are mixed.

With the unknown effects on future children, a lack of shared experimental notes/reports and ethical precautions, and a plea via youtube Dr. He only 34 years old is being shunned in the science community just days before his presentation at the Second International Summit on Human Genome Editing in Hong Kong.

AminoKassid

Strong Genes Equal Strong Immune System

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On January 12, 2019

In Student Post

Although scientists have long agreed that antibodies are in integral part of building up the body’s immune system, there is new evidence that strongly suggests genetic factors play a large role in determining how well the immune system builds and uses these antibodies when fighting disease.

https://commons.wikimedia.org/wiki/File:Redhead_twins.jpg

In a recent study, “researchers from James Cook University’s Australian Institute of Tropical Health and Medicine (AITHM) and the University of Queensland’s (UQ) Diamantina Institute have analyzed blood samples from 1835 twins and thousands of their siblings.” The team looked at the body’s immune response to “six common human viruses, including the Human Herpes virus, Parvovirus, Epstein Barr virus and the Coxsackie virus.” The team determined that genes passed down by parents are the major factor in how powerfully an immune system responds to diseases. “These genes determine whether you mount an intense or weak immune response when confronted with a viral infection,” says Associate Professor Miles.

“Demonstrating that antibody response is heritable is the first step in the eventual identification of individual genes that affect antibody response.” The researchers’ next goal is to identify the superior genes in order to, “imitate ‘super defenders’,” and “design next generation vaccines.”

 

Identical Twins, Identical Lives, Different Disease

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On March 9, 2015

In Student Post

Jack and Jeff Gernsheimer are identical twins. Jack has Parkinson’s disease, and his twin Jeff does not. Up until recently, because they have identical genomes, it would have been a mystery as to why Jack could develop Parkinson’s but not Jeff. However, with the discovery of epigenetics, scientists know that genes alone cannot explain why some people get Parkinson’s and other do not. While there are some genetic mutations linked to Parkinson’s, 90 percent of cases are “sporadic”, meaning that the disease did not run in the family. Even twins often do not develop Parkinson’s in tandem. Naturally, if genes don’t explain the development of Parkinson’s, scientists look to environment. There are several environmental factors that are known to link to the disease. People who were POW’s in WWII, for example, have a higher rate of developing Parkinson’s. But, and here’s the interesting part, Jack and Jeff have lived almost identical lives. For almost all of their lives, they have lived less than half a mile apart. Throughout their lives, they have been exposed to the same air, water, pesticides, etc. When they grew up, they built homes five minutes apart (by walk) on their father’s farm in Pennsylvania. Then, when they entered the professional life, they co-founded a design firm, working with their desks pushed up against each other.

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This anomaly, where a pair of humans exist with the same genetics and the same environment yet only one of them got sick is a research “bonanza” for scientists. All expected variables are being held constant, thus whatever is left must be deeply linked to the origins of Parkinson’s. However, there was a small difference in their lives that could provide insight into this anomaly. in 1968, Jack was drafted into the army and Jeff was not. This led to a series of unfortunate events in Jack’s life: first he served two years stateside in the military, got married, had two children, became involved in a long divorce, and suddenly his teenage son died. After this traumatic event, Jack went on to develop Parkinson’s, glaucoma, and prostate cancer, none of which Jeff has.

Jeff and Jack have been more than willing to undergo several studies in hope of finding something that could alleviate Jack’s Parkinson’s. The first study involved collecting embryonic stem cells from the twins. The benefit of stem cell cultures is that they act similarly to how they would in the body even though they are in a petri dish. The mid-brain dopaminergic neurons grown from Jack’s cells created abnormally low amounts of dopamine. Jeff’s produced normal amounts. Surprisingly, even though Jeff showed no signs of Parkinson’s, both twins had a mutation on a gene called GBA. This gene is known to be associated with Parkinson’s. As a result, both of their brain culture cells produced half the normal amount of beta-glucocerebrosidase, an enzyme linked to that gene. Instead of answering questions, this study only raised more to the fascinating case of Jeff and Jack.

I want to add a bit about how Jack’s son died, because it is unimaginably tragic and can show you just how much Jack had to face. Especially if we are considering Jack’s trauma as a contributor to his development of Parkinson’s, it is important to know the story. When Gabe, Jack’s son, was 14 in 1987, he became fascinated with the Vietnam War. Like any good father, Jack rented his son some movies on the war. One of those being The Deer Hunter, in which there is a scene where two prisoners of the Viet Cong are forced to play Russian Roulette. Gabe told his friend that if it were him, he wouldn’t just sit there. He would rather just get it over with. With that conversation, Gabe got his dad’s pistol, that he knew was hidden in the closet drawer, put one bullet in the chamber, put the gun to his head, and shot.

Jack rarely shows emotion. This “pressure cooker” way of dealing with things could explain his illness. Jeff thinks that the parkinson’s is a physical manifestation of how Jack deals with stress, rather how he doesn’t deal with stress. The connection between stress and disease is a very active research topic. And while their lives were very similar, if compared, Jack’s is by far the life with a more stressful environment. Some research might suggest that this stress differential can have a relation to Parkinson’s disease. In 2002, neuroscientists at UPitt subjected rats to stress, and they found that the stressed rats were more likely to experience damage to their dopamine-producing neurons than the non-stressed rats. This led to the term “neuroendangerment”, which means “rather than stress producing damage directly and immediately, it might increase the vulnerability of dopamine-producing cells to a subsequent insult.”

Another hypothesis as to what caused Jack’s Parkinson’s is that it could be linked to chronic inflammation.  Chronic inflammation is the mechanism by which stress can create neurodegeneration. Evidence that suggests this could be the case in Jack and Jeff is presented in their skin. Jack has psoriasis, a condition linked to chronic inflammation, and Jeff does not.

To this day, the search for what caused Jack’s Parkinson’s continues. Last year, NYSCF scientists conducted a study on the twins’ stem cells. They found a few functional differences between their cells. After finding the GBA mutation, they searched harder for other clues as to what might differentiate their brains. They screened 39,000 SNV’s, single nucleotide variants, which are instances where a single nucleotide in the human genome has been altered (either switched, deleted, or duplicated). They found 11 SNV’s, nine of which are linked to Parkinson’s disease. However, all 9 were found in both twins, meaning that this did not explain why Jack was sick and Jeff wasn’t.

Finally, they were able to uncover a relevant difference. Jack had high levels of MAO-B, which is involved in the breakdown of dopamine, whereas Jeff’s levels were close to normal.This hypothesis supposed that there exists a possible molecular mechanism by which stress could lead to neurodegeneration. What’s nice about this finding is that it could present a possible treatment for Parkinson’s. MAO-B inhibitors exist and are actually drugs currently on the market. They were given to Jack, and while it’s too soon to see the effects and to recommend them as treatment for Parkinson’s disease, it’s definitely a start.

Source: http://nautil.us/issue/21/information/did-grief-give-him-parkinsons

Identical but Not the Same

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On March 15, 2012

In Student Post

 

Some Rights Reserved. More Information: http://www.flickr.com/photos/timoni/3390886772/sizes/s/in/photostream/

After studying genetically inherited traits and diseases it could be easy to assume that genes determine everything about us. While it is true that colorblindness is a sex-linked trait – there is certainly more to the story.

Monozygotic “identical” twins are genetically identical, so they should be the same in all ways shouldn’t they?

Why, then, does one twin get early onset Alzheimer’s disease and the other “identical” twin doesn’t? The same is true for height, autism, and cancer. Although, when one twin has a disorder the other is more likely to get the disease also, that is not always the case.

In the January edition of National Geographic, author Peter Miller discusses the newest theories about how genes, environoment and epigenetics affect our life (and the end of it).

Twins offer scientists a unique opportunity to study how genetically identical people differ. Basically, that means scientists can study how things other than genes affect human development and lifespan. Already, scientists have found that a persons height is only 80% determined by genetics because the heights of “identical” twins differ by about .o8 on average. Using IQ tests, scientists have nearly disproved John Locke’s Tabula Rasa or blank slate theory (the idea that children are born with a blank mind that is either stimulated – (and made intelligent) – or not –  (kept unintelligent)). Specifically, scientists studied twins who had been separated at birth and adopted into different families. In this way, scientists have found that intelligence  is about 75% controlled by genetics.

So that leads to the question, what is it besides genes that affects us humans so drastically?

Environment has something to do with our differences. However, that cannot be the whole story. “The Jim Twins” as they are called in the twin science community, were studied in the 1870’s. They were adopted into different families where both boys were named Jim. Then went on to have the same jobs, marry wives of the same name (two Lynda’s first then two Betty’s), enjoy the same hobbies, enjoy the same brand of cigarette and beer, name their sons James Allan and James Alan… the list goes on. These two lived very similar lives, yet they grew up in very different environments. If environment isn’t the only factor in creating difference then what is?

Scientists have recently come to believe that epigenetics plays a significant role in our lives. Epigenetics (site 2) can be seen as the meshing of environment and DNA. In the words of author Peter Miller “If you think of our DNA as an immense piano keyboard and our genes as keys – each key seach key symbolizing a segment of DNA respinsible  for a particulare note or trait, and all the keys combining to make us who we are – then epigenetic prcesses determine when an how each key can be struck changing the tune.”  Environmental changes do have some impact.  When a pregnant mouse is put under stress during the pregnancy it can create changes in the fetus that lead to abnormal behavior as the rodent grows into adulthood.

However, scarily enough, many epigenetic changes appear to occur randomly (thus creating a probelm for the organized nature/nurture theory). Currently work is being done studying DNA methylation, which is known to make the expression of genes weaker or stronger. Specifically, Andrew Feinburg, director of the Center for Epigenetics at Johns Hopkins School of Medicine, is working to find how DNA methylation relates to autism. Currently, he is using scanners and computers to search samples of DNA from autistic twins who have the disease in varying degrees. He is looking to compare how and why

the genes are expressed differently.

In the end, all we know is that there is more to our future than our genes can tell us. Yes, our genes play a huge role in who we are as people – in terms of appearance, character, intelligence and more – but there are some variables that our environment and epigenetics control.

Main Article: Miller, Peter. “A Thing or Two About Twins.” National Geographic. Jan 2012: 38-65. Print.

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