Changes

[[Image:799.gif|right|thumb|300px]]

[[Image:799.gif|right|thumb|300px]]

'''Deoxyribonucleic acid''' (DNA) is a chemical inside [[cell]]s which carries the hereditary information. It is a molecular [[polymer]] formed of [[nucleotide|deoxyribonucleotides]]. Most organisms use DNA as their hereditary material. [[Offspring]] of [[Human reproduction|sexual reproduction]] [[Organism|organisms]] contain DNA from both parents.

'''Deoxyribonucleic acid''' (DNA) is a chemical inside [[cell]]s which carries the hereditary information. It is a molecular [[polymer]] formed of [[nucleotide|deoxyribonucleotides]]. Most organisms use DNA as their hereditary material. [[Offspring]] of [[Human reproduction|sexual reproduction]] [[organism]]s contain DNA from both parents.

==Structure==

==Structure==

Small lengths of DNA called [[gene]]s serve as the instructions for the body to carry out its functions and give rise to the physical traits of the organism.<ref>"Eye-color genes, through the proteins they encode, direct the amount and placement of melanin in the iris." [http://www.hhmi.org/cgi-bin/askascientist/highlight.pl?kw=&file=answers%2Fgenetics%2Fans_044.html Ask A Scientist - Genes and eye color]</ref> DNA is packaged into [[chromosomes]]. Each individual human being has 23 pairs of [[chromosome]]s, where one set is inherited from his/her mother and the other set is inherited from his/her father. 22 of these chromosomes are referred to as [[autosome]]s, while the remaining chromosomes are the sex chromosomes.  Males possess a single X chromosome and a single Y chromosome; whereas females possess a pair of X chromosomes.  In total, it is estimated that there are roughly 20300 protein-coding genes in the human genome. Due to mRNA splicing, it is estimated that these genes encode for over 1 million different protein products.

Small lengths of DNA called [[gene]]s serve as the instructions for the body to carry out its functions and give rise to the physical traits of the organism.<ref>"Eye-color genes, through the proteins they encode, direct the amount and placement of melanin in the iris." [http://www.hhmi.org/cgi-bin/askascientist/highlight.pl?kw=&file=answers%2Fgenetics%2Fans_044.html Ask A Scientist - Genes and eye color]</ref> DNA is packaged into [[chromosomes]]. Each individual human being has 23 pairs of [[chromosome]]s, where one set is inherited from his/her mother and the other set is inherited from his/her father. 22 of these chromosomes are referred to as [[autosome]]s, while the remaining chromosomes are the sex chromosomes.  Males possess a single X chromosome and a single Y chromosome; whereas females possess a pair of X chromosomes.  In total, it is estimated that there are roughly 20300 protein-coding genes in the human genome. Due to mRNA splicing, it is estimated that these genes encode for over 1 million different protein products.

DNA also contains sequences that regulate how and when genes are used by the cell and sequences for important RNA that is not translated into protein (parts of [[ribosome]], etc).  

DNA also contains sequences that regulate how and when genes are used by the cell and sequences for important RNA that is not translated into protein (parts of [[ribosome]], etc.).  

The "language" in that protein structure is described in DNA is called the [[genetic code]]. Genetic code is the same for all organisms, from human to plants and yeasts (few known exceptions are rare and just tiny deviations). The universality of the genetic code is difficult to explain from the evolutionary point of view. This universality makes possible to move the genes from one organism into another, where after the possible modifications (as a rule, regulatory sequences must be adjusted and introns removed) they often still work. For instance, human insulin is currently produced by modified yeasts or bacteria. Wider usage of the genetically modified organisms brings the known risks and ethical problems.

The "language" in that protein structure is described in DNA is called the [[genetic code]]. Genetic code is the same for all organisms, from human to plants and yeasts (few known exceptions are rare and just tiny deviations). The universality of the genetic code is difficult to explain from the evolutionary point of view. This universality makes possible to move the genes from one organism into another, where after the possible modifications (as a rule, regulatory sequences must be adjusted and introns removed) they often still work. For instance, human insulin is currently produced by modified yeasts or bacteria. Wider usage of the genetically modified organisms brings the known risks and ethical problems.