Science Fair Project Encyclopedia
A nucleic acid is a complex, high-molecular-weight biochemical macromolecule composed of nucleotide chains that convey genetic information. The most common nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleic acids are found in all living cells and viruses.
Highly simplified diagram of a double-stranded nucleic acid. Yellow circles represent phosphate; green circles represent pentose; red circles represent nitrogenous bases. Solid lines represent covalent bonds; dashed lines represent hydrogen bonds.
Nucleic acid, so called because of its prevalence in cellular nuclei, is the generic name of family of biopolymers. The monomers are called nucleotides, and each consists of three components: a nitrogenous heterocyclic base (either a purine or a pyrimidine), a pentose sugar, and a phosphate group. Different nucleic acid types differ in the specific sugar found in their chain (e.g. DNA or deoxyribonucleic acid contains 2-deoxyriboses). Also, the nitrogenous bases possible in the two nucleic acids are different: adenine, cytosine, and guanine are possible in both RNA and DNA, while thymine is possible only in DNA and uracil is possible only in RNA.
The sugars and phosphates in nucleic acids are connected to each other in an alternating chain through shared oxygens (forming a phosphodiester functional group). Using the conventional nomenclature, the carbons to which the phosphate groups are attached are the 3' and the 5' carbons. The bases extend from a glycosidic linkage to the 1' carbon of the pentose ring.
Nucleic acids may be single-stranded or double-stranded. A double-stranded nucleic acid consists of two single-stranded nucleic acids hydrogen-bonded together. RNA is usually single-stranded, but any given strand is likely to fold back upon itself to form double-helical regions. DNA is usually double-stranded, though some viruses have single-stranded DNA as their genome.
Hydrophobic interaction of nucleic acids is poorly understood.
Nucleic acids are insoluble in ethanol and insoluble in TCA.insoluble in cold water, hot water, dil HCl. Soluble in dil NaOH, alcohol and HCl
There are various common sources of DNA and RNA:
- Calf thymus DNA provides large linear DNA. It contains many breaks.
- T4 phage DNA is circular and can be isolated intact.
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