Have you ever asked yourself what exactly determines who you are? Why are you in the way that you are? Every single feature of your face, every detail of your body, every process that takes place in your body, including your mind, is determined by your genetic information. Everything is encoded and kept in the nucleus of each cell in your body.
The genetic information is stored in structures called chromosomes. Each chromosome contains of one DNA molecule and proteins. The deoxyribonucleic acid is in fact polymer. That is a large molecule that is made out of smaller, repeating molecules called monomers. The monomers of DNA are called nucleotides. Nucleotides are the same except the type of nucleobases. There are four types of nucleobases, therefore DNA is made out of four different nucleotides – Adenine (A), Guanine (G), Thymine (T) and Cytosine (C).
Every DNA molecule contains two strands, that run in opposite directions and are connected to each other by binding the nucleobases from the opposite nucleotides. Always A from one strand binds with T from the opposite strand and G from one strand binds with C from the opposite one. This is the way how genetic information is stored. The sequence of those nucleotids makes up the whole diversity of proteins and therefore of organisms. Yes, it is only four different nucleotides, but they are billions on one DNA molecule and the human genome has 46 chromosomes ( 23 different chromosomes that form pairs).
Perhaps you are asking how all of this has to do with the way you look and you think. Here is the answer. DNA has structural and functional parts called genes. Each gene has the information for a specific protein ( there are special techniques in different cells how from one simple gene similar but still distinguishing from each other proteins could be produced). So each gene has a specific nucleotides sequence, which is first transcribed into special molecules called RNA. The type of RNA that carries the information for synthesizing a protein is called messenger RNA or mRNA. The messenger RNA is then translated into a protein. This happens by the ribosomes which are special organels in the cells. The sequence of three nucleotides from mRNA codes one amino acid from the protein ( proteins are polymers made out of amino acids). For example, the sequence AGA stands for the amino acid Arginine.
This is how different proteins are produced in the cell. Proteins are the polymers that determine the structure and functions of each cells, tissues, organs. It is considered that the difference between people is due to the difference in the proteins that build them up.