BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: Nature vs. Nurture

Genes: They are influential in more ways than one

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.

 

 

Transgender- Science Behind Sexual Identity

Stop Homophobia - NUS Sports Gay Protests, London

Darren Johnson Image Link

Transgender concepts have been a prevalent issue. It has been seen on a celebrity level with Caitlyn Jenner but on smaller levels as well. Schools are struggling to make decisions of whether to make bathrooms same-sex or unisex. While administrative figures are struggling to make accommodations for the increasing number and popularity of LBGT rights, society is also struggling to determine whether trans-gender identity is a social or biological doing.

One recent finding has shown that anatomical sex- gender identity and orientation- is determined in the womb. However, once the anatomy is settled, there is about a six month lag before the brain masculinizes or feminizes. Research has concluded that through some combination of genetics, hormones and the uterine environment, sometime between six months and delivery the sexual orientation is set in the brain. The only question that rises is what happens when the brain does not match the genitals.

Genetics has been proved to play a role in transgender identity. Researches studied a group of twins where either one or both were transgender.  In identical twins, 39% were both transgender. Of the fraternal twins, there were zero pairs where both were transgender. In fact a study in the Journal Biological Psychiatry, researchers found a gene variant that was associated with being a trans woman.

For the 61% of identical twins where only one is transgender, the prenatal environment, or womb, had a key role. While identical twins share genetic codes, the genes that get expressed or remain unexpressed differ. Identical twins have separate umbilical cords , separate amniotic sacs, and develop in separate locations of the womb. All these things can have an affect in the mixing of chemicals and the sexual identity process.

Lastly, the structure of the brain also plays a role. A 2014 study from the Journal of Neuroscience found that “differences in the brain’s white matter tracts [fall] along a perfect spectrum of gender identity with cisgender men and women at the ends and trans men and women in the middle.”

 

Identical but Not the Same

 

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.

Powered by WordPress & Theme by Anders Norén

Skip to toolbar