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Why do our genes influence our health?

27.NOV.2023

Written by Anna Sanniti

Reviewed by Wendi Gill, CGC

We have roughly 20,000 genes that are spread across 23 chromosomes. We have two copies of each gene, one inherited from our mother, and the other from our father. An analogy we have used before is that each chromosome is a book in the library (the library being the genome) and each gene is a chapter in one of these books. Each chapter, or gene, provides different instructions for a process or physical characteristic in our bodies. In this article, we will discuss:

  • How a gene provides these instructions to the cell

  • What effect a genetic mutation has on proteins

  • What effect mutated proteins have on the body

How does a gene provide instructions to the cell?

Remember that a gene is a segment of DNA that codes for a protein. It is made up of a sequence of four bases: adenine (A), cytosine (C), guanine (G), and thymine (T) that form base pairs – A always pairs with T, and C always pairs with G. The sequence of these base pairs, also known as the genetic code, creates the instructions for building proteins. Proteins are molecules that carry out important jobs in our bodies, such as: 

  • digesting our food

  • creating new cells

  • supporting our immune system

  • building our hormones

  • repairing any damage to our DNA 

When the genetic code of a gene is needed, the DNA helix is unzipped and the code is copied into a molecule called messenger RNA, or mRNA. This is a very similar molecule to DNA, except it has a single strand instead of a double-helix, and thymine (T) is replaced with a similar base called uracil (U). This process is called transcription[1].

This mRNA molecule can now be used as a code to create a protein. Every 3 letters, called a codon, will code for a single building block of a protein called an amino acid. For example, GCA is the codon for an amino acid called alanine. There are 20 different amino acids in total that can be used to build proteins, each coded for using different combinations of 3 letters. This process will gradually build up a protein chain in a process called translation. There are also specific codons for starting to build a protein (AUG) and stopping (UAA, UAG, and UGA).

What effects does a genetic mutation have on proteins? 

A genetic mutation, for example, a change from “A” to “G” in the genetic code, will alter the associated codon. This may change the specific amino acid incorporated into the protein, which can change the shape of the protein and how it works in the body. Sometimes, a mutation will cause a stop codon to appear earlier than it should. This will cause the translation of a protein to stop early, meaning that the protein will not be fully formed, and will not work correctly.

What effects do mutated proteins have on the body?

A protein that contains different amino acids or is not fully formed due to an early stop codon, will behave differently. This is because the size and shape of a protein are very important for the job that the protein has in the body. For example, say an individual has a mutation in one copy of their BRCA1 gene that causes the protein to prematurely stop being made. The normal version of the gene will create a normal protein that can prevent the development of certain cancers by repairing DNA. The mutated version of the gene creates an abnormal protein, and this means that the protein created cannot work to repair DNA as effectively[3]. There are many examples of proteins not working as effectively following a genetic mutation, affecting many processes such as building and protecting muscle cells, creating blood cells, and carrying cholesterol into cells.

Let’s recap

  • The sequence of base pairs in a gene creates the instructions for building proteins. Proteins are molecules that carry out important jobs in our bodies.

  • When a gene is needed, the DNA helix is unzipped and the code is copied into a molecule called messenger RNA, or mRNA.

  • This mRNA molecule can now be used as a code to create a protein. Every 3 letters, called a codon, will code for a single building block of a protein called an amino acid. This process will gradually build up a protein chain. There is also a codon for starting to build a protein and stopping.

  • A genetic mutation will alter the associated codon and may change the specific amino acid incorporated into the protein.

  • Sometimes, a mutation will cause a stop codon to appear earlier than it should.

  • A protein that contains different amino acids or is not fully formed due to an early stop codon, will behave differently. This is because the size and shape of a protein are very important for the job that the protein has in the body. This can affect our health.

We encourage you to share all results with your healthcare providers. They can provide guidance based on your situation. Let them know if you have any concerns or questions.

References

1. National Human Genome Research Institute Educational Resources. Transcription. Online: genome.gov 2. National Human Genome Research Institute Educational Resources. Translation. Online: genome.gov 3. EPMA Journal. Founder BRCA1/2 mutations in Europe: implications for hereditary breast-ovarian cancer prevention and control. Online: springer.com