Continuing our journey towards understanding DNA, we will focus today on genes and genetics in general. I will try to answer this question: What is the purpose of genes? I believe the best way to understand a concept is by deconstructing the misconception about them. As such, today we will learn about genes by viewing 5 misconceptions about genetics.
Before we go into the misconception, some background on genetics is needed, especially on genes. In short, a gene is an instruction on how to make a protein. The best analogy to understand genes is the barcode analogy: When you want to buy an item in a store, there is a barcode you need to scan to get the price. You can’t understand the barcode just by looking at it though, it needs to be scanned first. Once scanned, you can see the price, and then pay. Similarly, DNA is unreadable by the protein-making machinery (also called ribosomes). However, some proteins will scan specific genes and create a more readable version of the gene, called messenger ribonucleic acid, or mRNA for short. The making of mRNA from DNA is called DNA transcription. Ribosomes can then read mRNA and produce the protein of interest, in a process called translation. [source / source / source]
Next, I want to talk about proteins. While this is a word very often used in the context of nutrition, its role in the body is not very well defined. In general, everything that we think happens in our body is due to a protein. They are responsible for every thing that keeps us alive. One of the most famous protein is hemoglobin, which is a protein in blood cells whose function is to transport oxygen. Insulin is also a more known protein, and it is a hormone that is important for the regulation of sugar. Most proteins follow the same template: They have one or more specific function that they perform over and over until replaced. There are thousands of different protein, each with specific roles essential for our body function. In short, proteins are essential for survival, and the DNA is simply the recipe book for making proteins. Now that you know more about genes, we will talk about the misconceptions about genetics. [source / source / source]
Misconception 1: X gene will get you sick
This misconception is seen the most in media. For example, one of the most talked about is the BRCA1 gene. We often see article saying that people with the BRCA1 gene will have breast cancer. This is false, simply because everyone has the same gene. However, people have different variations of the genes, called alleles. Over time, mutations in the DNA happen, creating slightly different forms of the same genes. These alleles are then transmitted and are now an integral part of the DNA of many people. While most alleles for a gene are similar in function, some can increase the cause of diseases. This is the case of the BRCA1 gene: having a specific allele for this gene increases the risk of breast cancer. [source / source / source / source]
Misconception 2: genes are the only cause of some traits
Since we consider DNA the cause of our existence, people have the tendency to think that genes are the only reason for who we are. However, this is false, else we would look very similar to chimpanzee, as we share about 96% of our DNA with them. In reality, there is a lot that goes into the formation of humans. A lot is genetic yes, for example different expression of genes at different locations, but environment plays a huge role as well. One example that is rarely talked about is epigenetics. Epigenetics are DNA modification without mutations. Simply put, some genes are « tagged », and each tag will tell the cell to stop expressing this gene or to express it a lot more. Many epigenetic modifications are due to environmental cues such as exposure to certain food for example. Epigenetics are one of the many ways we separate ourselves with chimpanzees. [source / source / source]
Misconception 3: All mutations are dangerous
Most people, upon hearing the word mutation, will fear for diseases or other problems. This is a legitimate concern: some mutations will be the cause of diseases, like diabetes Type I or some forms of Alzheimer’s. However, most mutations are actually benign. Simply put, a mutation is a mistake in the DNA sequence that was made when the DNA was replicating itself. Most mutations simply causes different alleles that are fully functioning. Some mutations are actually helpful. For example, there is a mutation called CCR5-delta32 that modifies the structure of the protein CCR5, which is important for cellular movement. But more importantly, CCR5 is the protein used by the virus HIV to enter cell, potentially causing AIDS. Well the CCR5-delta32 mutations makes people immune to HIV/AIDS, since the virus cannot interact with CCR5. This beneficial mutation is under a lot of studies to find a potential vaccine against HIV/AIDS. In short, most mutations do not do anything, but they are also the cause of very beneficial changes and they are the start of evolution, as they allow us to have new traits that may be useful to us. [source / source / source]
Misconception 4: one gene = one trait
A lot of people will think you have one gene for hair color, or one gene for the formation of the brain. However that is false, since many traits are created by multiple genes. These traits are called polygenic. Example of polygenic traits include height, hair color, weight, etc. Some traits are indeed monogenic though, meaning caused by one gene. One example is the ability to roll your tongue or not. [source / source / source]
Misconception 5: 50% from father 50% from mother
This argument is a common one among the pro-life movement: a baby is made up of 50% of their mother and 50% of their father. Well this is not true. The 50/50 inheritance pattern only apply to what is called the genomic DNA. This DNA is the DNA we have been talking about since the beginning: the DNA that creates most of the proteins. However, there is another DNA subset that is solely transmitted from the mother: mitochondrial DNA, or mitDNA. The paternal mitDNA is destroyed and only the maternal one is kept. Recently, some researcher have found paternal transmission of mitDNA, but this is a rare case most likely caused by a mutation preventing the destruction of the DNA. Regardless, the mother also transmits other parts, such as important proteins, energy, and building blocks for the cells. As such, an embryo is made up of 95% of their mother, and 5% of their father. [source / source]
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