Dna

abbreviation of deoxyribonucleic acid organic chemical of complex molecular structure that is found in all prokaryotic and eukaryotic cells and in many viruses. DNA codes genetic information for the transmission of inherited traits.

Art:Figure 1: Portion of polynucleotide chain of deoxyribonucleic acid (DNA). The inset shows the ...

* Figure 1: Portion of polynucleotide chain of deoxyribonucleic acid (DNA). The inset shows the ...

Art:Figure 2: The bases of one helical strand in DNA are paired with complementary bases of the other ...

* Figure 2: The bases of one helical strand in DNA are paired with complementary bases of the other ...

The chemical DNA was first discovered in 1869, but its role in genetic inheritance was not demonstrated until 1943. In 1953, James Watson and Francis Crick determined that the structure of DNA is a double-helix polymer, a spiral consisting of two DNA strands wound around each other. Each strand is composed of a long chain of monomer nucleotides. The nucleotide of DNA consists of a deoxyribose sugar molecule to which is attached a phosphate group and one of four nitrogenous bases: two purines (adenine and guanine) and two pyrimidines (cytosine and thymine). The nucleotides are joined together by covalent bonds between the phosphate of one nucleotide and the sugar of the next, forming a phosphate-sugar backbone from which the nitrogenous bases protrude. (See Figure 1.) One strand is held to another by hydrogen bonds between the bases; the sequencing of this bonding is specific--i.e., adenine bonds only with thymine, and cytosine only with guanine. (See Figure 2.)

The configuration of the DNA molecule is highly stable, allowing it to act as a template for the replication of new DNA molecules, as well as for the production (transcription) of the related RNA (ribonucleic acid) molecule. A segment of DNA that codes for the cell's synthesis of a specific protein is called a gene.

Art:Figure 3: A possible method