Nucleic acid structure

Nucleic acid structure refers to the structure of nucleic acids, such as DNA and RNA. These structures are essential for the storage and expression of genetic information in living organisms. Nucleic acids are composed of nucleotides, which are the building blocks of DNA and RNA.

Primary structure

The primary structure of nucleic acids is the linear sequence of nucleotides. Each nucleotide consists of a phosphate group, a sugar (deoxyribose in DNA and ribose in RNA), and a nucleobase. The sequence of these nucleotides encodes genetic information.

Secondary structure

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The four nucleobases of DNA: adenine, cytosine, guanine, and thymine.

The secondary structure of nucleic acids refers to the local interactions between nucleotides, such as base pairing. In DNA, the most common secondary structure is the double helix, where two strands are held together by hydrogen bonds between complementary bases (adenine with thymine, and guanine with cytosine).

RNA secondary structure

RNA secondary structure is more varied and can include hairpin loops, bulges, and internal loops. These structures are important for the function of RNA molecules.

Tertiary structure

The tertiary structure of nucleic acids refers to the three-dimensional shape formed by the folding of the secondary structure. This includes the overall shape of the DNA double helix and the complex folding of RNA molecules.

Predicted secondary structure of an RNA molecule.

Quaternary structure

Quaternary structure involves the higher-order organization of nucleic acids, such as the packaging of DNA into chromatin in eukaryotic cells. This level of structure is crucial for the regulation of gene expression and DNA replication.

File:DNA to Chromatin Formation.jpg

DNA is packaged into chromatin in eukaryotic cells.

DNA conformations

DNA can adopt several conformations, including A-DNA, B-DNA, and Z-DNA. These conformations differ in their helical structure and are influenced by environmental conditions such as humidity and ionic strength.

Side view of A-DNA, B-DNA, and Z-DNA conformations.

Holliday junctions

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A Holliday junction, a key intermediate in genetic recombination.

Holliday junctions are a type of DNA structure that occurs during the process of genetic recombination. They are formed when two double-stranded DNA molecules exchange strands, creating a cross-shaped structure.

Related pages

• DNA
• RNA
• Nucleotide
• Base pairing
• Chromatin
• Genetic recombination