What are DNA, Genes & Chromosomes? Let's talk simply!

Have you ever wondered what made you the way you are? How is your hair color, eye color, height, your body shape, all of this determined? The answer lies in these things we're going to talk about today, DNA , genes, and chromosomes . Although they may sound like a bit of scientific jargon, these are very simple things to understand. Let's take a look.

What is DNA (Deoxyribonucleic acid)? Simply put…

Think of your entire body as a big instruction book. That book tells you how every part of your body should work, how you should look, and how you should look. That set of instructions is called `DNA (Deoxyribonucleic acid).` It is in every cell in your body. Simply put, DNA is the blueprint of who you are.

What is DNA made of?

DNA also has its own language to write this instruction book. That language has four letters. They are:

• Adenine (A)
• Cytosine (Cytosine – C)
• Thiamine (Thymine – T)
• Guanine (Guanine – G)

These four chemical bases are what make up the “words” in your instruction book, arranged in a certain order. Just like our Sinhala letters are put together to make words. Imagine, there are about 3 billion of these bases in the human body! 99% of them are the same for every person. That remaining 1% is what makes you different from others, your own unique person. Isn’t it amazing?

DNA is constantly making copies of itself. That is, it makes copies of your body's instruction manual, like handwritten copies. It uses the words that are formed by combining those bases.

So what are genes?

Genes are, in essence, like the building blocks of your body . Some genes give instructions for making proteins. The function of proteins is to tell your body what physical characteristics you want to have. For example, things like the color of your hair and the color of your eyes. Some genes encode something called `RNA (Ribonucleic acid),` which carries out other functions.

How do we get genes?

You can't buy these genes from the gene store. You get them from your mother and your father. To be precise, you get one copy of your genes from your mother's egg and one copy from your father's sperm . Once you have a pair of genes, those genes divide, make copies of themselves, and work until they fill your entire instruction book. Imagine, there are between 20,000 and 25,000 genes in your body!

Now let's see what chromosomes are.

Chromosomes are thread-like structures. They are located in the center of cells, in the nucleus. Chromosomes contain DNA and proteins. They come in different sizes. They are made up of special proteins called `Histones` that make them compact and spaced out inside the nucleus. Just think, without those histones, our chromosomes would be as tall as we are! Chromosomes are the exact instructions your cells receive that make you special and unique.

How many chromosomes do humans have?

Normally, a healthy person should have 23 pairs of chromosomes (46 in total). These chromosomes are divided into 22 numbered pairs (called `autosomes`) and a pair of sex chromosomes (the `X` and `Y` chromosomes). You get one pair from your mother and one from your father.

However, very rarely, mistakes can occur when cells divide and make copies. When this happens, some people may have an extra chromosome in a pair (a condition called `Trisomy`) or one chromosome in a pair may be missing (a condition called `Monosomy`).

What is the relationship between DNA, genes, and chromosomes? How do they work?

These three elements - DNA, genes, and chromosomes - come together and work together to create the person you are.

• Chromosomes are what carry DNA inside cells.
• DNA is responsible for building and maintaining your human structure.
• Genes are parts of your DNA that give you your unique physical characteristics and make you different from others.

Simply put, when all of this comes together, your body receives a complete set of instructions that determine how your cells should behave.

Where is DNA located? How can it be seen?

DNA is in every cell in your body. Most of it is in the nucleus (center) of each cell. There is also some DNA in the mitochondria (the small organelles inside cells that produce energy).

As for the appearance of DNA, it is made up of the four chemical bases mentioned earlier: adenine (A), cytosine (C), thymine (T), and guanine (G). These base pairs come together in pairs; A always pairs with T, and C always pairs with G. These base pairs, together with a sugar molecule and a phosphate molecule (called a `nucleotide`), form a spiral staircase-like shape (also called a `double helix`). The base pairs are like the rungs of a staircase, and the sugar and phosphate are like the handrails.

How do chromosomes look?

Chromosomes have a thread-like structure. Chromosomal proteins (the aforementioned `histones`) wrap around DNA, like a thread wrapping around a spool of thread, compressing the DNA into small pieces to fit inside cells. Imagine, if the chromosomes didn't wrap around DNA like that, your DNA would be about 6 feet long from end to end!

What are Genetic Conditions?

A genetic condition is a disease caused by an abnormal gene. A genetic mutation is a gene that is not copied correctly during cell division. That is, its sequence or shape is different from other genes in the body. If you have a genetic mutation, your body may not be able to grow and function normally.

Sometimes you can inherit this gene mutation from your parents. Sometimes you can also develop the gene mutation in your body by chance, without anyone in your family having had the mutation or genetic condition before. There are thousands of genetic conditions like this.

How do genetic mutations occur?

Genetic mutations occur when your cells divide and make new cells. When cells divide, they are like hand-writing the original version of your body's instruction manual. There is a lot of room for mistakes in this process. It's like skipping a page or a chapter when you're reading a book. If you make a mistake (a genetic mutation), your instruction manual can give your body the wrong instructions. Sometimes the mutation doesn't change the way your body works. But sometimes the mutation can prevent you from functioning normally. It all depends on what kind of thing that gene is coding for.

Are there tests that can check the health status of my genes?

Yes, there are many genetic tests. These use a sample of your blood, skin, hair, or, if you are pregnant, amniotic fluid. These tests can identify changes in your genes, chromosomes, or proteins. These tests can pinpoint specific genetic conditions and mutated genes. Also, if you are hoping to have a child, these tests can help you find out the risk of having a child with a genetic condition.

How can I improve the health of my DNA?

To improve the health of your DNA, you need to take good care of your body. Because your DNA is responsible for how you grow and function. You can improve your overall health by:

• Eat a well- balanced diet .
• Exercise.
• Maintain a healthy weight.
• Avoid smoking and using tobacco products.

What is a Homologous Chromosome?

A homologous chromosome is a pair of chromosomes, one from the mother and one from the father. Both must have the same genetic information, in the same places. Chromosomes can also be nonhomologous. This means that the genetic information they contain is different, or is in different places.

Finally, what to remember (Take-Home Message)

Your DNA, genes, and chromosomes are some of the most important parts that make you who you are. Although they are too small to be seen with the naked eye, the role they play is amazing and very big. So, it is up to you to follow a healthy lifestyle and keep your DNA, genes, and chromosomes working well. If you love yourself, think about these little friends inside your body. Only if they are well can you be well.