What Actually is Your Genome, DNA, and RNA?
By: Brian Hoeflinger, MD
June 29, 2025 | #52
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Disclaimer: Opinions are my own. Not medical advice.
In Partnership with Nucleus Genomics
Medical Trivia of the Week
What percent of the DNA sequence is the same across all human beings? (the correct answer is at the end of this email)
- A) 25%
- B) 50%
- C) 80%
- D) 99.9%
How Your Genome Works: The Instruction Manual for You
Your genome, in the simplest of terms, is the complete set of instructions to make your entire body. But how do these “instructions” actually get put into action to create you?
Let’s start with the basics.
What Is DNA?
The basic building block of your genome is DNA, which carries all of your genetic information. Each strand of DNA contains a unique chemical code that guides your growth, development, and overall health.
DNA is organized into structures called chromosomes. Humans have 23 pairs of chromosomes, one set inherited from each parent.
Every single cell in your body contains a complete copy of your genome. That’s mind-boggling when you consider that the human body is made up of billions of cells. Theoretically, any one of these cells could be used to create a replica of you.
From DNA to Genes to Chromosomes
- Genes are specific segments of DNA that contain the instructions for making proteins, these proteins build and maintain your body.
- Your genes determine characteristics like eye color, hair color, and height.
- Genes live on strands of DNA, and those DNA strands are tightly coiled into chromosomes.
- These 23 pairs of chromosomes are what make up your genome, and each and every cell in your body contains this full genome within its nucleus.
What Is DNA Made Of?
DNA itself is made up of four nucleotide bases:
Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).
The sequence of these bases acts like a chemical code, a biological version of computer code, telling your cells what to do and how to build your body.
Enter RNA: The Messenger
To fully understand how the genome operates, we need to introduce another molecule: RNA (Ribonucleic Acid).
- RNA is similar to DNA but has one strand instead of two, and it uses Uracil (U) instead of Thymine (T).
- Inside the cell nucleus, RNA copies the genetic code from DNA.
- These RNA strands then exit the nucleus and travel to ribosomes, the protein factories of the cell.
- The ribosomes read the RNA and build proteins based on the genetic instructions.
So the process goes like this:
DNA → RNA → Ribosomes → Proteins → You
What If Something Goes Wrong?
If the sequence of your DNA changes, it results in a mutation.
Mutations can be caused by:
- UV radiation from sunlight
- Cigarette smoke
- Environmental toxins
- Or even occur spontaneously
Thankfully, your body has repair mechanisms to correct most mutations, but they’re not perfect. Some mutations sneak through and become permanent parts of your DNA.
Why Do Mutations Matter?
- Many mutations are harmless.
- Some can lead to genetic disorders, cancer, or other diseases.
- When a mutation becomes permanent, it can be passed down to future generations.
- This is how inherited conditions, like Huntington’s disease, certain cancers, or arthritis, are passed from parent to child.
This inheritance is also why biological families often share similar physical traits, like height, facial structure, eye color, and more.
In Summary
Every cell in your body contains a genome, a complete set of instructions for building and maintaining you. These instructions are encoded in DNA, made up of four bases: A, T, C, and G. Segments of DNA form genes, which guide protein production. Genes are stored on chromosomes, which are bundled inside your cell nucleus.
RNA copies the DNA code and carries it to ribosomes, where proteins are built to carry out all functions of life.
Understanding your genome helps you understand you, and how both health and disease can be passed down through generations.
Take Control of Your Health
I am proudly partnered with Nucleus Genomics because I strongly believe their robust genetic testing represents the future of preventative medicine.
Nucleus Genomics offers a whole-genome DNA test as well as partner carrier screening. Genetic testing technology has come incredibly far in a short time: Nucleus uncovers your genetic risk for 900+ conditions — cancers, heart disease, mental health, and more. You can also link your Nucleus profile with your partner’s to identify any shared carrier status, helping you understand your combined risk of passing on recessive conditions and make informed family-planning decisions.
Join thousands, including me, who have used Nucleus Genomics to test their DNA and discover their genetic insights.
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Impactful Quote of the Week
"You can always recognize truth by its beauty and simplicity"
- Richard Feynman
All my best,
Brian Hoeflinger
P.S. - if you enjoyed this newsletter, you may enjoy my book that details my life as neurosurgeon and the loss of my oldest son, Brian (see below a synopsis).
My Book
Life and Death . . . Two words with such opposite meaning and which inflict such contradictory emotions and yet are so closely intertwined in our lives. As parents, we bring meaning and life into this world through our children. Our lives become defined as a result. We learn the joy, hardship, and responsibility of shaping an innocent life. But a day will come when that life will be taken. For some, death will come too soon. This is the story of my son, Brian Nicholas Hoeflinger, who died unexpectedly at age 18.
https://doctorhoeflinger.com/products/the-night-he-died-the-harsh-reality-of-teenage-drinking
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Medical Trivia Answer:
The correct answer is D) 99.9
*Disclaimer: This newsletter and blog is for general informational purposes only and does not constitute the practice of medicine, nursing, or other professional health care services, including the giving of medical advice, and no doctor/patient relationship is formed. The use of information on this newsletter and blog or materials linked from this newsletter and blog is at the user’s own risk. The content of this newsletter and blog is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Users should not disregard or delay seeking medical advice for any medical condition they may have and should consult their healthcare professionals for any such conditions.
