Cells to Chromosomes

A Galaxy Within Ourself

Before you move on to learn the wonders of life, you have to learn the basics. You can't learn about the awe-inspiring DNA double helix before you learn about what contains it. Here, you will learn the fundamentals of genetic science. In other words, you will learn about the breathtaking legacy of the cell.

Every human body is made of billions of cells. Within each cell, there is a nucleus. This is where the secret to life lies. The center of the cell, or nucleus, contains the machinery necessary to produce protein, which is the basic building block of living tissue. Protein comes in every shape, size, and form you can imagine, on a microscopic scale, of course. The smallest building block of protein is amino acid. There are twenty amino acids that are assembled in various sequences to produce the different proteins that are used to make nerve, muscle, and bone. The recipe for building these proteins is written in a code contained within the chromosomes on strands of deoxyribonucleic acids, or DNA, which you will learn about in the appropriately titled section, "DNA".

Chromosomes are individual collections of lengths of DNA. Every cell in your body from your kidney to your toe carries exactly the same set of chromosomes, each made of the same specific chemical structure. Human cells have twenty-three pairs of chromosomes (forty-six in all), while gorillas have twenty-four, and mice have twenty. The chromosomal structure of every species is different, and the specific DNA sequence within those chromosomes is unique from person to person, gorilla to gorilla, and mouse to mouse. You inherit one set of the twenty-three from your mother and the other set from your father. Your father had an X chromosome and a Y chromosome, which made him a man, and your mother had two X's, making her a woman.

These chromosomes determine your sex, just like all other chromosomes in your body determine some trait about you. The chromosomes are copied each time a cell divides and each new cell receives an identical copy of them (except when a cell performs "Meiosis").

Now we get down to the code itself, the blueprint for life. Deoxyribonucleic acid is a long, coiled molecule constructed of four nucleotides in a specific sequence. The nucleotides are adenine, thymine , guanine, and cytosine (or A, T, C, and G). They are arranged in varying sequences that ultimately code for proteins. This surprisingly simple sequence allows for nearly limitless possibilities.

Introduction
Cells to Chromosomes
DNA
RNA
Genetic Cycle