DNA

Bases in DNA

...

bacteriophage

A virus that infects bacteria

base pairing rules

A with T: the purine adenine (A) always pairs with the pyrimidine thymine (T) C with G: the pyrimidine cytosine (C) always pairs with the purine guanine (G)

DNA polymerase

An enzyme that catalyzes the elongation of new DNA at a replication fork by the addition of nucleotides to the existing chain.

Nitrogenous base

An organic base that contains nitrogen, such as a purine or pyrimidine; a subunit of a nucleotide in DNA and RNA

Strand makeup of the two DNA molecule made during reproduction

DNA is an example of a macromolecule, i.e. a large molecule with a special shape, which is built up from many smaller parts called sub-units . If you could magnify part of a nucleus, you would see the DNA molecule looking like a twisted rope ladder - a double helix. The two strands forming the sides of the ladder give it a strong yet flexible structure, which does not vary along its length. Stretched between these are the "rungs" of the ladder, the parts of the DNA molecule which vary, and so the differences carry genetic information. These parts are made up of sections called bases, which fit together in pairs. Single section of DNA The 4 bases (so called because on their own they react with acids) are also usually known by their initials, as shown alongside: A (adenine), paired with T (thymine) and C (cytosine) paired with G (guanine).

Nucleotide

In a nucleic-acid chain, a subunit that consists of a sugar, a phosphate, and a nitrogenous base

Monomer of DNA

Nucleotides are the monomer of DNA. They are made of a 5-carbon sugar (deoxyribose), a phosphate group, and a nitrogenous base bound to the sugar. The four different types of nucleotides are adenine (A), thymine (T), guanine (G) and cytosine (C). Deoxyribose makes up the backbone of the DNA double helix when two molecules of DNA bind together. The nitrogenous bases bind specifically between the two DNA molecules to form the structure of DNA. Adenine and thymine bind together, and guanine and cytosine bind together. The specific binding is because of the chemical and physical properties of the monomers. It allows DNA to have the double-helix shape.

double helix

Shape of DNA

Makeup of a nucleotide in DNA

The nucleotide in DNA consists of a sugar (deoxyribose), one of four bases (cytosine (C), thymine (T), adenine (A), guanine (G)), and a phosphate. Cytosine and thymine are pyrimidine bases, while adenine and guanine are purine bases. The sugar and the base together are called a nucleoside.