Everything You Need to Know About Your Genes
Learn these 6 basic things and you’ll be well on your way to feeling pretty comfortable about your DNA and genes.
These days everyone wants to know all about their genes and what they might learn about themselves if they knew their DNA (genomic) sequence.
Do I have any bad genes that could make me sick? Do I carry any bad genes that I might pass on to my child that will make them sick? How come my hair is black and my Mom’s is brown? Why am I so much taller than my Mom and Dad? Who am I related to? What is my ancestry? And the list goes on and on….
What I want to do in this article is to give you just enough information about your genes so that you‘re fairly comfortable when someone starts talking about genes, genetics and genomes.
I’ll talk about what genes are, where they are found, what a genetic trait is and how genes work to produce the traits we associate with them. I’ll also look at how genes mutate and how that can result in a disease.
So let’s get some basics on what are genes are composed of, where our genes are and are not and what we might learn from all this.
Here’s the 6 things you most commonly need to know about your genes.
1. What are Genes?
Once upon a time we didn’t even know there was such a thing as a gene. All we knew was that if we bred plants or animals and selected for traits that we preferred, over many generations these efforts would often reward us with the kind of plant or animal we were hoping for.
Or if my Mom and my Dad had blonde hair, it was a good bet that their children would also have blonde hair.
Then, in modern times, we discovered DNA and that it contained thousands of specific regions that actually coded for and specified different traits.
In 2001 the first draft of the human genome was compiled and published and was a major milestone in understanding our DNA and our genes. Subsequent analysis put the number of genes in humans at 20-25,000 give or take a few.
Which led to the next question.
2. Where are my genes located?
Almost all of your 20,000 or so genes are located on the 46 chromosomes (23 from Mom and 23 from Dad) that are in the nucleus of every cell in your body (with the exception of your red blood cells, which do not contain nuclei). There are 37 additional genes that are located on one single circular chromosome in our mitochondria, organelles that are also found in every cell in your body.
3. What is a genetic trait?
We all know many of the physical traits that we can see easily such as how tall a person is, what colour their eyes or hair is, what colour their skin is, what shape their nose is etc. These are all specified to some degree by your genes.
4. Are all traits set in stone?
This is another area where there is a lot of confusion. There are several reasons for this. The first reason is that some genes are more “potent” than others. We call these genes dominant, and their less potent partners, recessive. Everyone who took a biology course in high school knows about Gregor Mendel’s breeding experiments that he conducted from 1856 to 1863 with peas. In peas, purple flowers are always dominant over white flowers and smooth peas always win out over wrinkled. After looking at 7 different traits, he established rules of heredity that came to be known as the laws of Mendelian inheritance. For simple traits, these laws worked quite well.
There are genes that can be modified by different genes and so are neither fully dominant nor fully recessive.
And then there are genes that have lots of copies, not just one. And these copies can all modify each other.
So some traits are very simple, and some are highly complex.
And then some genes can be mutated.
5. What are mutations?
As we mentioned above, our genes are specific sections of DNA found on our chromosomes. The DNA is a long chain and is made up of 4 different biochemical molecules, abbreviated as A, T, G & C, that make up the actual sequence of the DNA. An example of a bit of DNA that has had its 4 molecules sequenced and identified as shown below in the image from a popular sequencing method.
A mutation occurs when the order of the A, T, G & C molecules differ from the usual expected sequence. So if the sequence in the figure above was the expected one and instead, yours started with GAC then the C might be a mutation that replaced the original T that is in the 3rd place. I say might be because there is often substantial variation at certain positions in a given gene’s sequence and until you sequence many people’s DNA you don’t know the range of common variations that are not considered to be mutations.
We normally think of mutations as negative alterations. In horror movies, it’s always the mutants that takeover Earth and we have to save ourselves from them! But in reality, there are also positive mutations that lead to better outcomes for an organism.
For that reason, I personally don’t like to use the term mutation unless it refers to a change that has a detrimental effect. I prefer to use the term alteration.
How many kinds of alterations are there?
There are a variety of different kinds of alterations that range from changes of single molecules like we saw above, to changes in whole groups of these 4 molecules. Some alterations have no effect and others have profound effects.
This is a huge topic to fully cover in this article. Just know that there are 3 categories of mutations or alterations.
- Those that have no effect and are referred to as neutral alterations,
- Those that have a positive effect
- Those that have a negative or detrimental effect on the organism.
Ok, I’ve got a gene that is altered. Am I going to get sick?
Not necessarily. Remember some alterations are neutral and have no effect, some are actually beneficial and make us stronger in some way. It’s only the negative ones that can result in disease.
6. How can genes produce diseases?
There are several ways that genes can produce diseases. The most common is to have a mutated copy or copies which produce a protein that doesn’t function properly or the protein isn’t even made in the first place. Sickle Cell Anemia is a classic example of this.
Hemoglobin is found in your red blood cells and its function is to carry oxygen to the various tissues in your body. Normal hemoglobin works just fine to carry oxygen to your bodies cells but, if there is a mutation in this gene, then it doesn’t carry oxygen nearly as efficiently. It also has an abnormal tendency to form long chains of itself that cause the red blood cells to take on a crescent or sickle shape instead of their normal round shape. They don’t survive as long (normal red blood cells usually live for about 120 days while sickled cells only last 10–20 days) and can cause many problems.
Another possibility is sometimes a gene or part of a chromosome is duplicated and then you have extra copies of a gene or several genes. An example of this is trisomy 21. Trisomy means 3 copies. So there is an extra copy or piece of chromosome 21 (we normally only have 2 copies of each chromosome, one from Mom and one from Dad). This trisomy usually results in Down syndrome.
We could go on and give examples about other alterations in genes and other conditions that can arise but I think you get the general idea. When there is a alteration that has negative consequences, we can get sick and in some cases, even die because of it.
And that pretty much covers the basics of what you need to know about your genes.
Look, there are whole books about genes so we can’t go into too much detail here!
7. Should I get my DNA sequenced?
Here’s an “extra credit” piece that could also be the source of another whole article.
And it’s a common question these days.
For the sake of brevity, let me ask you this.
What do you want to know?
Do you just want to see if you can find a few relatives and ancestors on a genealogy site? Then yeah, go ahead and do it.
But suppose you had a mutated gene that could result in you coming down with a disease that happens later in life such as Huntington’s disease. Would you want to know about that? Would you be comfortable knowing you had that mutation?
Some people are and some people aren’t.
Or do you want to know if there is a possibility that you passed on any detrimental genes to your children? Again, some folks want to know and some don’t. If you knew, how would you tell your child? Would you get an abortion?
And what about gene therapy?
These are very difficult questions and I don’t want to address them in this article.
I think I’ve given you pretty much all the basics that you need to understand your genes and how they work.
So let’s call it quits for now.
If you’d like me to go into more detail in future articles, please let me know in the comments below. I’d love to hear from you 😄
Until next time,
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