Formally known as Deoxyribonucleic acid, DNA is the code within biological cells that captures the instructions on how to make different proteins that govern the cells function and form. They consist of long, linear strands of base-pairs consisting of only 4 basic building block molecules. These molecules, in pairs or triples, define larger proteins that, when strung together, create genes and other material that define particular functions. Most of the DNA resides in chromosome strands.
Every human cell has a nucleus with 46 chromosomes. Each chromosome has a type label of either 1 to 22 or X or Y. The numeric labeled chromosomes are called autosomes and conveniently shortened to atDNA on this site. The sex or Allosome chromosomes are X and Y and indicated with shortened names of xDNA and yDNA, respectively, on this site. Almost all cells have a pair of closely matching, numeric-labeled chromosomes and two Allosome chromosomes and this is termed the diploid. There are approximately 6.4 billion base pairs in these 46 chromosomes of the diploid. When only talking about the sex cells, which just have a single copy of each autosome and only either an X or Y, then this is termed the haploid. Just the collection of the unique chromosomes (that includes X and Y is also termed the genome.
Often overlooked, there is DNA in the cell body, outside the nucleus, as well. These mitochondria structures also contain a ring DNA molecule very similar to the nuclear-residing chromosomes. Mitochondria are important not only for their function in the cell but also in that only the egg copy survives the reproduction process as the sperm copy is destroyed. Thus mitochondria are always passed on only from the mother who produces the egg to her children. We shorten the mitochondria reference to mtDNA in this site.
All DNA is built in the well-known "double helix" structure. This is not to be confused with the fact that each nucleus of the cell has a pair of numbered chromosome. That is to say, for example, there are two similar (but not identical) copies of chromosome 22 in every cell and each chromosome 22 is built as a double-helix structure. When the "double helix" is straightened out (unwound from the tight, multi-layer knot it exists in naturally, it can be viewed as a ladder with the base pairs forming the rungs. If the rungs are broken down the middle, each rail of the ladder contains a single sequence of the basic building molecules. These strands that combine to form a double-helix are different but containing the same coded information. One is often defined as the forward strand and the other the reverse strand so a reference of the start for the DNA can be made.
Every human cell has a nucleus with 46 chromosomes. Each chromosome has a type label of either 1 to 22 or X or Y. The numeric labeled chromosomes are called autosomes and conveniently shortened to atDNA on this site. The sex or Allosome chromosomes are X and Y and indicated with shortened names of xDNA and yDNA, respectively, on this site. Almost all cells have a pair of closely matching, numeric-labeled chromosomes and two Allosome chromosomes and this is termed the diploid. There are approximately 6.4 billion base pairs in these 46 chromosomes of the diploid. When only talking about the sex cells, which just have a single copy of each autosome and only either an X or Y, then this is termed the haploid. Just the collection of the unique chromosomes (that includes X and Y is also termed the genome.
Often overlooked, there is DNA in the cell body, outside the nucleus, as well. These mitochondria structures also contain a ring DNA molecule very similar to the nuclear-residing chromosomes. Mitochondria are important not only for their function in the cell but also in that only the egg copy survives the reproduction process as the sperm copy is destroyed. Thus mitochondria are always passed on only from the mother who produces the egg to her children. We shorten the mitochondria reference to mtDNA in this site.
All DNA is built in the well-known "double helix" structure. This is not to be confused with the fact that each nucleus of the cell has a pair of numbered chromosome. That is to say, for example, there are two similar (but not identical) copies of chromosome 22 in every cell and each chromosome 22 is built as a double-helix structure. When the "double helix" is straightened out (unwound from the tight, multi-layer knot it exists in naturally, it can be viewed as a ladder with the base pairs forming the rungs. If the rungs are broken down the middle, each rail of the ladder contains a single sequence of the basic building molecules. These strands that combine to form a double-helix are different but containing the same coded information. One is often defined as the forward strand and the other the reverse strand so a reference of the start for the DNA can be made.