What does a gene do?

Welcome to the Genetic Lifehacks “Getting Started with Genetics” course. 

This is a concise four-lessons long course on how to use your genetic data to optimize your diet and health. 

My goal is to explain genetics to you in a way that is easy to understand – with lots of practical examples. Instead of being a formal course, this will be more like a conversation about genetics. 

So what exactly does a gene do?

A friend asked me that question recently…  a friend that I had talked to a lot about genetics. The question made me realize that a lot of people have a general, fuzzy idea about what a gene is, but they don’t always understand the underlying science. For a lot of us, it has been many years since biology class in high school. 

Simply put… 

Genes are the instructions, or the code, for a protein

We often think of protein as something we eat. For example, you might eat a steak or some eggs to get some protein.  

In biology, though, a protein just means a series of amino acids that are bound together.  

In your body, proteins make up the structure of a cell, and they act as enzymes that cause a reaction to take place. Proteins can also act as signals to regulate other functions taking place in the cell. 

A lot of the genes that we will talk about in this course will code for proteins that act as enzymes. These enzymes are going to cause a reaction to take place in the cell – acting as a catalyst to make the reaction occur.

Example time: The MTHFR gene codes for the methylenetetrahydrofolate reductase enzyme that acts within the folate cycle. (Quick tip: If a word ends in ‘-ase’ it is usually an enzyme). Within the cell, the folate that you get from eating some green vegetables must go through a series of steps to be used by the body. That final chemical reaction step is ‘catalyzed’ or caused by the MTHFR enzyme. A common genetic variant in the MTHFR gene causes the enzyme not to function as well as the typical variant. Take a quick minute and check your genetic data to see whether you carry the MTHFR C677T variant.
Check your genetic data for rs1801133 (23andMe v4, v5; AncestryDNA):
  • G/G: typical *
  • A/G: one copy of MTHFR C677T allele, enzyme function decreased by 40%
  • A/A: two copies of MTHFR C677T, enzyme function decreased by 70 – 80%
Members: Your genotype for rs1801133 is .
If you carry the variant (A/G or A/A), your MTHFR enzyme doesn’t work as well as the typical version of this gene. This means the body won’t produce quite as much of the active form of folate (methylfolate). Digging a little deeper: Enzymes only work at specific temperatures and at the right pH. This little change in the DNA code for the MTHFR gene causes the enzyme to be more sensitive to temperature, and it breaks down more quickly at normal body temp. You can read all about the effects of this MTHFR variant here.

Back to enzymes (proteins):

We have lots of different enzymes in the body. These enzymes help to break apart the food we eat, cause reactions to take place within the cells, and initiate the transcription of genes – to create more proteins.

Genetic variants – changes in proteins: 

Small changes to the way a protein is put together can change the way a protein works. Other changes can cause the protein not to work at all, which is usually bad… 

Genetic changes affecting enzymes can cause reactions in cells to take place more slowly than normal – or more quickly.  

Changes to structural proteins can cause problems with the way that cells function. Or, some changes just cause something really minor – such as hair color differences.


One thing that fascinates me about genetics is the overarching resilience that it shows us. In the example above with the MTHFR gene, a lot of people have variants that decrease the enzyme function. But the body has backup routes and other ways of dealing with the decrease in folate. 

This resilience is what Genetic Lifehacks is all about. If you have a variant that decreases a cellular function, you can figure out how to bypass that and optimize your health.

To recap: 

Genes code for proteins.

Proteins do most of the work in a cell:

  • act as enzymes to cause a reaction to take place
  • make up the structure of cells
  • transport molecules within cells and outside of cells
  • send signals to start or end a process

We are resilient and just need to figure out what is best for each of us, individually.

Video with more details on how DNA is turned into a protein: