Genetics 101

Genetics 101

Cells, Chromosomes, and DNA

The human body consists of approximately 50 trillion cells, each with unique jobs. The genetic code controls cellular differentiation and determines which cells will become bone, muscle, blood, and so on. The bone cells keep our skeletal system strong; muscle cells help us move and pump blood; and blood cells transport oxygen throughout the body. Almost every cell has a nucleus that contains chromosomes, which are made up of genes. Genes tell these cells what to do; they are the specific recipe that tells our body how to function.

Genes are made up of DNA (DeoxyriboNucleic Acid). If each gene is a recipe, the DNA molecules are the words of that recipe. DNA is made up of a set of letters - A, T, G, C - all representing molecules (Adenine, Thymine, Cytosine, Guanine) that combine in groups of 2 to form base pairs.

The order of the letters is very important, as it tells the genes how to function. Each gene usually has a single function. For example, some genes tell the body how to color the iris and differences in these genes produce different eye colors. Every function of the body is controlled by one or more genes, including the way we break down food, metabolize medication, or mount an immune response to a pathogen.

The genetic code of a human being consists of 3.2 billion base pairs. They are split into 23 "packages" called chromosomes and, on average, a chromosome contains about 1000 different genes. 

Where do our genes come from?

Genes are passed down from generation to generation. Your genes come directly from your two biological parents. Each person has two sets of genes, one from your biological mother and one from your biological father.

When the genes from your two biological parents combine, the genes are shuffled (a process called recombination) to create your unique set of two pairs of 23 chromosomes. Each person is the unique product of generations of accumulation and combination of different genetic traits.

99.5% of DNA is shared between all humans, the 0.5% remaining is what makes each person unique.  

What is a genetic variant and how do they happen?

Our genes are not completely error-free. In order to grow, our cells divide and copy to make more cells. The DNA copying process is not perfect, and can sometimes produce errors. The body has built-in mechanisms to catch and fix these errors, but occasionally mistakes are made and a genetic variant makes it through. 

As cells continue to copy, these errors become permanent fixtures in our bodies, creating genetic variations. Genetic variants are the parts of DNA that differ from person to person and make us unique. They can occur throughout a person's lifetime or be passed from one generation to the next.

One type of variant is called a SNP (single nucleotide polymorphism), which is a difference in a single DNA base. For example, some people may have an A in a specific location while other people may have a T. SNPs are often what are looked at in genetic testing.

Why do genetic variants matter? 

Many genetic variants cause no harm and often go undetected. Other variations, or mutations, cause catastrophic consequences and lead to the death of the cell, and are rarely passed from one generation to another. However, there are some genetic variants that can cause cells to function differently or incorrectly. This can contribute to different traits or increased risk for certain diseases.

Some genetic variants have developed over time to help us live in a completely different world, while other traits in our genes create negative effects when our body interacts with the modern environment. For example, the genetic predisposition to store dietary fat quickly and lose it slowly was beneficial for our ancient ancestors when food was scarce. This adaptation meant they had a better chance of surviving because their body’s could efficiently store energy. However, in the modern world, this trait can be harmful because food is plentiful and it is easy to gain weight and hard to lose it.

Certain genetic variants have even more profound effects on health, increasing the risk of heart attacks, triggering asthma and allergies, causing lactose intolerance and many other disorders. While some genetic variants lead to inevitable health conditions, most genetic variants simply increase the overall risk of developing a disease.

For example, a person may have genetic variants that increase their risk for diabetes. However, not everyone at risk for diabetes actually develops the disease. Furthermore, even people with a high risk of diabetes can lower their risk through lifestyle changes, like diet and exercise, preventative medication, and some targeted supplemental nutrients. In these cases, knowledge is power and understanding a predisposed health risk can alert the individual to take enhanced proactive measures.

Other genetic traits only cause illness when they are triggered by a specific environmental feature. For example, lactose intolerance is a genetic condition that causes a person who drinks milk (or consumes lactose-containing products) to have digestive issues. A lactose-intolerant person who does not consume these products will not have any symptoms. Again, this genetic understanding can be incredibly beneficial to the individual and help guide daily decisions. 

What is genetic testing and what is the value?

There are many types of genetic tests available both for direct purchase and through a doctor. Tests related to wellness and health often analyze specific genetic variants through sample collection (either saliva or blood). Many tests look at specific SNPs to identify the gene variants and determine personal health risks and strengths.

The results from these tests can help you understand which genetic variants you have, and what the potential consequences for those variants are. In many cases, taking advantage of this knowledge, following some precautionary measures, health risks may be mitigated. This is the next step in preventive and personalized medicine, and signals a new generation of health care.

How do scientists know how to understand genes?

Like all other research, DNA research uses the scientific method. Genetic science is a newer discipline and research is evolving rapidly with the advancement of testing and sequencing technology. For this reason, single stand-alone research results should be considered carefully.

The most compelling information comes when there are multiple studies showing the same impact of specific genetic variants on diseases or other health conditions.

About Rootine

Co-founded by molecular biologist and genetic scientist, Dr. Daniel Wallerstorfer, PhD, Rootine creates science-backed daily vitamins formulated precisely for each individual's needs based on their DNA, blood level, and lifestyle data. Rootine also offers at-home DNA nutrient testing and in-depth reporting. Rootine tests specific inherited genetic variations that impact nutrient requirements. Dr. Wallerstorfer has been at the forefront of nutrigenetic research (how genes impact nutrition) for 10+ years.