APR 21, 2017 01:55 PM PDT

Genetically Speaking, Two X Chromosomes are Better than One

WRITTEN BY: Xuan Pham

From different external sex organs, to different organization of internal sex organs, to presence of different hormones, and different secondary sexual characteristics, males and females have many causes for sex differences in disease that can be traced back to the genetics of X and Y.

Due to these differences, some diseases occur only in males and others only in females. The presence of the Y chromosome or lack thereof, is important in sex-specific diseases. Y-linked diseases such as azoospermia can only affect males because, by definition, only males carry the Y-chromosome. Similarly diseases that affect the sex organs are also sex-specific. Testicular and prostate cancers are maladies that affect only males because these organs are absent in females. In contrast, ovarian cancers are limited to females.

The imbalance of the X chromosome number between males and females is corrected via X-inactivation, the process by which one of the two X chromosomes in females is inactivated early in embryogenesis. X-inactivation in humans is random - the cell may activate the paternal or the maternal X chromosome; however the inactivated X stays inactivated in all daughter cells. From the point of diseases, it can be argued that males are at a disadvantage for having just one X chromosome. Because of X-inactivation, females have a 50% chance of inactivating an X chromosome that harbors a deleterious mutation while the normal X chromosome is the only active one. Males, on the other hand, have the same chances (100%) of inheriting a mutated X chromosome as they do a normal one. The odds are apparent when evaluating X-linked diseases such as hemophilia and color blindness, where the majority of affected individuals are males.
About the Author
  • I am a human geneticist, passionate about telling stories to make science more engaging and approachable. Find more of my writing at the Hopkins BioMedical Odyssey blog and at TheGeneTwist.com.
You May Also Like
SEP 11, 2018
Videos
SEP 11, 2018
Eat Mediterranean Food and Live Longer?
In southern European countries, the "Mediterranean Diet" is widespread and lauded as a healthy way to eat. It’s caught on all over the worl...
SEP 12, 2018
Health & Medicine
SEP 12, 2018
Before You Tear the Moldy Portion of Your Bread Off and Call it Good... Watch This
While most people cringe at the thought of a moldy piece of bread lurking in their refrigerator, there exist bolder people who will gladly tear the moldy b...
SEP 16, 2018
Videos
SEP 16, 2018
Diseases Lurking in Our Backyards
Despite being invisible, microbes surround us all the time. They cover our phones, our hands, and infiltrate our backyards. Although a lot of these microbe...
SEP 20, 2018
Videos
SEP 20, 2018
The Lowdown on Vaccine Development and Production
Learn more about how vaccines are developed and tested, from the CDC....
OCT 17, 2018
Space & Astronomy
OCT 17, 2018
Should We Build a Space Elevator?
Rockets are the primary means of sending cargo to and from space, but chemical burns are incredibly expensive, and this has some firms looking into alterna...
OCT 21, 2018
Videos
OCT 21, 2018
Rare Footage of the 'Headless Chicken Monster'
The headless chicken monster is actually a deep-sea swimming sea cucumber scientifically known as, Enypniastes eximia. The strange creature was seen on fil...
Loading Comments...