DNA is a molecule found in all organisms, consisting of nucleotides joined together to form a polynucleotide. The sequence of nucleotides determines the genetic code, which determines the proteins formed in a cell, ultimately controlling its structure and function. DNA consists of two complementary strands joined by hydrogen bonds, forming an alpha double helix structure.
Deoxyribonucleic acid, or DNA, is the molecule that contains the genetic material of all organisms. It is found in most viruses, all bacteria, and all plant and animal cells. DNA is found within the nucleus, or control center, of the cell. It can also be found within the mitochondria and chloroplasts, in those cells that have them, such as plants.
A deoxyribonucleic acid molecule consists of a long chain of nucleotides. Nucleotide molecules are formed when a five-carbon sugar molecule, a pentose sugar, joins a phosphate group and an organic base. Within a DNA molecule, the sugar is deoxyribose and the organic bases can be adenine, thymine, cytosine or guanine.
DNA molecules are macromolecules. They consist of many subunits which are similar or identical to each other. The subunits, the nucleotides, are joined end to end, similar to a string of pearls. Deoxyribonucleic acid is a polynucleotide, but is usually referred to as a nucleic acid.
Individual nucleotides are joined between the phosphate group of one and the sugar molecule of another. A condensation reaction takes place to bring the two nucleotides together and also produces water. The sugar and phosphate group are the same throughout the length of the chain, but any of the four bases can be attached to the sugar.
A DNA molecule consists of two complementary strands of nucleotides joined together by hydrogen bonds between the bases. Each base can only bond with one other base. Specifically, adenine always pairs with thymine and cytosine always pairs with guanine. Between adenine and thymine there are two hydrogen bonds and between cytosine and guanine there are three bonds. The two nucleotide strands wrap around each other to form an alpha double helix structure.
The specific sequence of nucleotides along the deoxyribonucleic acid molecule is what determines the genetic code of each cell. Genes are made up of lengths of nucleotides along a DNA molecule. They are sequences of nucleotide triplets along the deoxyribonucleic acid molecule. These triplets determine which amino acids will be used to make proteins. Specific base triplets code for different amino acids.
The genetic code of the DNA molecule determines which proteins are to be formed in a cell. Different chemical reactions take place within different cells depending on the cell type and its function. These chemical reactions are controlled by enzymes, which are proteins. Thus DNA determines the structure and function of a cell based on the fact that the sequence of nucleotides specifies which proteins are to be formed and when.
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