What are genes? How are proteins made? What is a mutation?

What are genes? Genes are splices of our DNA. We inherit our DNA from our parents, roughly one half from each parent. The same DNA exists in each cell of our body inside the nucleus of the cell. In its most condensed form the DNA exists in tightly coiled structures called Chromosomes. The human DNA is made up from 23 pairs of chromosomes. In each pair of chromosomes one chromosome is inherited from each parent. One such pair of chromosomes is referred to as the sex chromosomes. One sex chromosome is inherited from each parent. A sex chromosome is either a X chromosome or a Y chromosome. In females both sex chromosomes are X chromosomes and in males one chromosome is X and the other is Y. So females are XX and males are XY. The sex chromosomes along with the 22 other pairs of chromosomes make up the DNA. They largely determine how our cells make proteins and enzymes that are essential to the various biochemical reactions that are constantly taking place within our cells. 

How are proteins produced in our cells? Genes, that is DNA fragments, are first transcribed into RNA, and then translated into amino acid chains called proteins. The translation into proteins takes place in cell structures called ribosomes. The proteins are then packaged and used within the cells or they leave the cell by a process called exocytosis. The proteins travel in the blood and are received into other cells by processes such as endocytosis and transport across cell membranes. The process by which genes become proteins is usually referred to as gene expression. Not all gene fragments are expressed into proteins. The mechanism which determines which genes are turned on or off for gene expression is called gene regulation. Certain points in the DNA are marked primarily by a process called DNA methylation. The methylation is then used as a guide for gene regulation. Gene regulation is determined by a variety of environmental things such as diet, drugs, sunlight,  stress as well as internal factors such as hormones and metabolism. 

To summarize the main function of genes is to make proteins and these proteins participate in almost all biochemical processes in our body from cell function to organ function, organ systems, endocrine system and immune system. 

What is a mutation? A mutation happens when a small portion of a gene changes in a random manner. A mutation that happens when a sperm cell or an egg cell is formed is called a hereditary mutation and can be passed along to the progeny. Other mutations are called acquired or somatic mutations that arise from environmental factors such as exposure to radiation or an error in the cell division (DNA replication) process. These are not passed along to the next generation. Somatic mutations are not transmittable to other cells in the body but only to those cells that arise from replication or division of the cell with the mutated DNA. Most mutations are harmless but certain mutations can cause a malfunction in protein generation and could lead to diseases such as cancer.