DNA, which stands for deoxyribonucleic acid, is a molecule that supplies the hereditary instructions that tell living creatures how to develop, live and reproduce. DNA can be found inside every cell and is passed down from parents to their offspring.
DNA is made up of molecules called nucleotides. Each nucleotide contains three components: a phosphate group, which is one phosphorus atom bonded to four oxygen atoms; a sugar molecule; and a nitrogen base. The four types of nitrogen bases are adenine (A), thymine (T), guanine (G) and cytosine (C), and together, these serve as the “letters” that make up the genetic code of our DNA.
Nucleotides are attached along with her to form a few much time strands one to spiral to help make a pattern entitled a dual helix. If you feel of double-helix design because the a hierarchy, the brand new phosphate and you can sugar molecules is the edges, because legs pairs may be the rungs. The bases on a single string couple to the bases to your several other strand: Adenine pairs with thymine (A-T), and guanine sets which have cytosine (G-C).
Human DNA is made up of around 3 billion base pairs, and more than 99% of those bases are the same in all people, according to the U.S. National Library away from Medicine (NLM).
Similar to the way that letters in the alphabet can be arranged to form words, the order of nitrogen bases in a DNA sequence forms family genes, which, in the language of the cell, tell cells how to make necessary protein. The shorthand for this process is that genes “encode” proteins.
But DNA is not the direct template for protein production. To make a protein, the cell makes a copy of the gene, using not DNA but ribonucleic acid, or RNA. RNA shares a similar structure to DNA, except it contains only one strand, rather than two – so it looks like just one half of a ladder. In addition, while RNA has three of the four nitrogen bases in common with DNA, it uses a base called uracil rather than thymine to pair with adenine.
As a cell prepares to build a new protein, its DNA unzips to expose one strand of the gene with the instructions to build said protein. Then, an enzyme zooms in and constructs a new RNA molecule whose sequence mirrors that of the unzipped gene. This RNA copy, called messenger RNA (mRNA), tells the cell’s protein-making machinery which proteins to string together into a protein, according to “Biochemistry” (W. H. Freeman and Company, 2002).
DNA molecules are long – so long, in fact, that they can’t fit into cells without the right packaging. To fit inside cells, DNA is coiled tightly to form structures called chromosomes. Each chromosome contains a single DNA molecule, wrapped tightly around spool-like proteins called histones, which provide chromosomes their structure. Humans have 23 pairs of chromosomes, which are found inside each cell’s nucleus, the control center of the cell.
Most chromosomes look like microscopic Xs; that said, humans and most other mammals carry a pair of sex chromosomes that can be either X or Y-shaped, according to Federal People Genome Look Institute. But there is some natural variation in the number of sex chromosomes people carry – sometimes, there may be extra sex chromosomes, or one might be missing, so other patterns, such as X, XXX, XXY and XXYY, can also occur, See stated.
DNA was first observed by Swiss biochemist Friedrich Miescher in 1869, according to a paper published in 2005 in the journal Developmental Biology. Miescher used biochemical methods to isolate DNA – which he then called nuclein – from white blood cells and sperm, and determined that it was very different from protein. (The term “nucleic acid” derives from “nuclein.”)