I hope you waited patiently for Part 2  of of my take on  NPR’s “Fresh Air.”  Siddhartha Mukhera won the Pulitzer Prize in General Non-fiction for The Emperor of all Maladies:  A Biography of Cancer in 2011.  He’s like the Carl Sagan of medicine.  He explains things in a way that both simplifies and enthrall.  Part 1 is here.  STEM Tuesday: GENE by Siddhartha Mukherjee

A quick recap about Siddhartha:  He’s an oncologist and a cancer researcher.  He has a PhD from Stanford University of Oxford where he studied cancer-causing viruses and he’s a graduate of Harvard Medical School.  Siddhartha works on discovering new treatments for cancer using innovative biological methods.

“Fresh Air” talked to him about his new book The Gene:  An Intimate History.  I took notes from the 45-minute podcast to create my post. I my first post, I summarized some of the things Siddhartha has to say about Genes and cancer.  Today, I’ll tell you some fascinating gene discovery about sexuality and sexual identity.

According to Siddhartha, the “Centerpiece of the book is that [tweetthis]biology is not destiny…some aspects of biology and some aspects of destiny are commanded very strongly by genes.”[/tweetthis]

First a bit about epigenetic.

Have you ever wondered about how a kidney cell, a skin cell and a nerve cell can have such different functions, and at the same time have exactly the same genetic make up.  When I took developmental biology, what back when, I learned that the same cells that become skin, also develop into the digestive system.  Some of  the same responses are common between the two types of cells.  For example, when we blush or pale as an emotional response, so does our intestines.  We have the same type of allergic response in our guts as we do on our skin.

Even the term epigenetics is in a bit of a turmoil because it means “on top of the gene.”   The genome is not a passive blueprint.  Proteins regulate how it gets  activated, inactivated and there’s a whole release cascades. Plus, master regulators can recruit other cells to combine their work.

Identical twins are great to study because they have the same genetic code. Yet, their genes are not expressed identically. If one twin has schizophrenia the other is 3-5  more likely to have it than the general population. However, it’s not a 1:1 link. Environmental factors over time, and in utero have an impact in whether the gene gets expressed.   It’s the same thing for  most chronic diseases.  If one twin develops the disease, the chances are 20% the other will too.

Women who carry the Brca gene  are at a strikingly high risk for breast cancer, yet not everyone who carries the Brca gene develops breast cancer.

 

Sexuality and Sexual Identity

Scientists know that there is one gene on the Y chromosomes that determines anatomy.  This gene is a master regulator gene.

[tweetthis]Almost all of the studies about homosexuality involved men.[/tweetthis]  Again, identical male twins tell us a lot.  Although the chances twins will share the same sexual orientation is higher than among siblings, it’s not  100% the same.  There are some other factors that have a powerful effect on sexual orientation, which involve more than a single gene, but rather, scientists believe there are many genetic determinants, and also sociological and environmental influencers of the gene expression.     Siddhartha stresses the “need to be clear or we end up fostering nonsensical controversy.” Although there he doubts there will be a “gay gene” identified, sexual orientation does have a genetic component.

We seem to know more about how gender identity works.  Discrepancy between anatomy and identity.

One gene determines anatomy, which  sits on the Y chromosome. It happens to be a master regulator game. There are cases where a person inherits the Y chromosome, but the anatomy and identity is female.  But for the most part, the anatomical gender matches the genetic gender. That said, there are many discrepancies between sexual anatomy and identity.

You probably remember from earlier that a master regulator recruits cells to do downstream things. In other words, master regulator cells are the commanders.  The chain of command is a cascade of events with  infinite variations along the hierarchy.  Slight or radical variations can result in gender identity shifts.  The ways the commands percolate can be very radically from one person to another, creating infinite ripples or variations in individuals. I recently heard that there are oner 50 sexual identifications to choose from.  Facebook recognizes 51.  If you’re interested here’s a link  to what those identities are:  Facebook’s gender identities.

What about genetic testing?

Biology is not destiny.  some aspects are commanded very strongly by genes.  Thousand of variations influence our destiny.  Although we are learning a lot about genetics, the truth is in the details, which are yet to be discovered. “Without a clear understanding we can be easily lead into discourse that is incorrect.”

Siddhartha cautions against genetic testing for diseases unless there’s a very strong 1:1 connection  Even though he has schizophrenia in his family and he knows that gives him a genetic predisposition, he chose not to be tested until there are answers that are more predictive.  Right now we’re nowhere close.  He doesn’t want to be a “previvor,” someone who thinks of himself as having a disease that has not yet manifested.  “Until we can create a better map, I won’t be tested. However he feels differently about the Brca gene.  “If history of breast cancer is striking enough, I recommend it to my patients.”

Siddhartha reminds us how much we are alike.

[tweetthis] “Genes are a massive plea for equality. We have deep similarities and a few dissimilarities.”[/tweetthis]