By Christine Rappleye
The genes inside cells have the codes which determine what a person looks like, what they will pass on to their posterity and what they received from their parents.
It is DNA, deoxyribonucleic acid.
Cells are the basic unit in a living systems, such as human beings. Within the cell''s nucleus are DNA strands which control the activities of the cell, and therefore the system.
The Basics
A genome is the complete set of DNA in an organism. Other than mature red blood cells, all human cells contain a complete genome.
Human DNA contains in two parallel strands which spiral around forming a double helix connected by nitrogen-containing chemicals called bases. There are four bases in DNA: adenine (A), thymine (T), cytosine (C), and guanine (G). Two bases bond together forming base pair rungs across the double helix. These pairs are combined together by weak bonds.
Each base has a complementary match that it only pairs with. Adenine only combines with thymine, and cytosine only combines with guanine.
Each strand contains a series of nucleotides, which are one base, one phosphate and one sugar. These nucleotides string together to form compatible halves of the DNA helix.
The order of the bases is denoted by the letter of the base, i.e. ATTGCAAGCG. This DNA squence dictates the exact instructions needed to create the organism''s traits.
There are more than 3 million base pairs in a genome. If untangled, the genome would stretch out five feet but would be only 50 trillionths of an inch wide.
Building blocks
When a cell splits into two cells, the whole genome is duplicated. In humans, the duplication is in the nucleus. The DNA strands unwind, the weak bonds between the base pairs break and the strands separate. The bases then fuse with its complementary base pair, thus creating a new strand. Each new cell receives an old strand of DNA coupled with a new strand of DNA. The genome is exactly reproduced and the cells continue to function.
When the reproduction isn''t exact, errors or mutations occur. These mutations are what cause the coding to be off and create differences that could result in genetic diseases.
Section by Section
The human genome''s DNA is arranged into 24 chromosomes. A specific sequences of bases that encode to create proteins are genes. These proteins govern all of life'' functions. The human genome has about 30,000 to 40,000 genes.
The genes make up the chromosomes. There are two sets of chromosomes, one from each parent.
Changes, however slight, in the DNA sequence create mutations that are responsible for many inherited diseases, predispose people for cancer, and other diseases.
Coding the Genome
Cracking the code to the human genome sequence will unlock information to start preventing genetic diseases. Every person''s DNA is unique to them and through genetic coding, a person can be identified through their genes.
Source: http://www.ornl.gov/hgmis/