Why do people look different?

Author: Layal Bou Abdo, MSN

Illustrator: Angeline Boswell

04/15/2020

Did your child ever ask you why people look different? Even though we have the same organs from the inside, from the outside, no one looks, the same.

“Mum, what makes us look different?”

“Our hair colour can be blond, black, gray, white, or brown.

Our eye colour can be black, brown, hazel, green or blue

Our skin colour can be fair, medium or dark

Our general outside appearance, our features, the shape of our eyes, nose and eyebrows all make us look different

The nature of our hair can be wavy, straight or curly

Our height can be different

Even our behaviour and personality can be different

…. And many more aspects that make us look unique.”

 That’s why people look different!

Your child has a moment of silence, …. a sigh…. Then here comes the BIG why!

“Ok mum, but why? Why I am tiny and short?”

It’s all written in your DNA….

The way a person looks is a combination of mum and dad. Skin colour, for example, is a mix of like how blue and yellow make green.

Parents pass their look from the DNA; so, a child has half of his DNA from mom and a half from dad.

But what is DNA?

DNA or Deoxyribonucleic Acid is like the instruction manual to make all parts of your body. Think of when you buy building blocks and, you are about to build an airplane. You have the instruction manual, different shapes of blocks and the airplane as the results of all the blocks built together in a certain way.  The airplane is you (your body); the instruction manual is your DNA. You can find DNA in almost every cell in your body – even the cells that constitute your toes, heart, face, etc.

How does it look like?

The DNA looks like a beautiful spiral ladder: it is a busy polymerase (an enzyme that synthesizes long chains of polymers or nucleic acids).  Each DNA molecule makes up a single chromosome. In total, we have 46 chromosomes (23 from mom and 23 from Dad) in our body. Thus, it’s the instructions for the body and these instructions are spelled out with 4 letters: ACGT, called Nucleotides. Those letters are linked together to help form the genes.

Meet our Nucleotides: adenine (A), cytosine (C), guanine (G), and thymine (T). As we mentioned before, a DNA molecule consists of two chains twisting around each other like a spiral ladder, held together by a bond between the bases.  So, adenine pairs with thymine, and cytosine pairs with guanine. The sequence of bases in a part of a DNA molecule called a gene carries the instructions needed to make the eyes green and the hair curly. In particular, there are over twenty thousand genes in the 46 chromosomes.

But how do they work?

Well because the DNA is super important it needs to stay safe inside the Nucleus; like a clubhouse in our cells. Therefore, the polymerase copies the genes and sends a copy outside of the nucleus to the builder, the ribosome. This copy is called RNA or Ribonucleic Acid. Thus, RNA is a temporary copy of some of the DNA. Yet, it is special because it actually replaces Thymine with a bonus nucleotide called Uracil (U). Why? Because U is easier for the cell to use for making proteins.

To explain, the “genetic code” is the term we use for the way that the four bases of DNA -the A, C, G, and Ts- are linked together. Afterwards, the ribosome reads the order of the nucleotides on the RNA strand, the genetic code and tells us what kind of protein they form. The proteins are therefore, the building blocks for the entire body. They make everything from skin, to genes, to hair, to organs.

Let’s focus more on the proteins!

In the genetic code, every three nucleotides or triplets, code for a single amino acid. In fact, hundreds or sometimes thousands of amino acids make the proteins, so the code that would make one protein could have thousands of triplets in it. The proteins then, come together to form a cell. Furthermore, the cells come together to form the body organs. There are millions of proteins created from the DNA that are unique to each person. One small change in the amino acids and the ribosome will read a different kind of protein. Consequently, if we slightly change the instruction manual of our building blocks, we will have a slightly different airplane. There is endless of sequences that your body can make out of the nucleotides and that’s how people look different!

To make things simple:

–    Trillions of little tiny cells make up a human

–    Inside those cells, there are 46 chromosomes

–    While looking closely at those chromosomes, you will see a spiral ladder called DNA; everyone’s DNA is a little different.

–    Genes are sections of the DNA. They hold instructions (the genetic code) to build all parts of the body

–    Those instructions are written using different patterns and sequences of only 4 letters As, Cs, Gs and Ts, the nucleotides

–    Copies of the DNA, called RNA, are made and sent out to the ribosomes

–    The ribosomes read those instructions to form proteins.

–    Lastly, proteins form all the body parts making all people look different!

Fun Fact

Did you know that no two people have the same DNA? Even identical twins; they share similar genes but not an identical DNA.

Did you know that DNA and RNA are also found bacterias and viruses?

We are certain your kid asks you health (human & animal) questions that genuinely leave you stumped! Leave a comment below and we are happy to answer “why” in future blogs.

Copyright © 2020 Little Medical School Ottawa