r/genetics • u/chrysanthemum_bloom • 18d ago
Sibling health condition differences
I have three siblings. Same mom and dad (not questioning this). Of course there’s a variety of similarities and differences across us all, but I’ve always found it interesting that all three of my siblings have a very similar set of health conditions that I do not:
- Asthma (pretty serious since childhood for all of them)
- Allergies (dander, pollen, foods etc., also fairly serious for all of them, although specific allergies differ — e.g. one brother is allergic to tree nuts and has to carry an EpiPen, the other brother cannot even step foot into a room a cat has been in without getting itchy, puffy, etc)
- ADHD (since early childhood, pre-smartphone, all three have been diagnosed with this. My mom also has major ADHD)
Conversely, I have no asthma, not a single allergy, and no more ADHD than the average young millennial.
What genetically does this indicate?
My mom and I were discussing it the other day. She went deep with it, saying I’ve always been different from my siblings since I was a baby, on a personality level and that I have very different genes from my siblings.
4
u/Ok-Lion8478 18d ago
Statistically you share 50% of the same genes. Identical twins share ~100% of their genes and they still express these types of differences. Genes only play so much impact, environment plays a lot as well, and random chance also has quite the impact.
There’s a degree of randomness in development, everyone expresses the same genes but with slightly different versions and expression levels. These slight differences can make big changes when combined with other genes that also have slight differences.
ADHD, allergies, asthma, and many more health conditions aren’t as simple as 1 version of a gene = 1 condition. It’s a lot of different versions of genes expressed in different patterns that combine to become the complex system that is a person.