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However, branched DNA can occur if a third strand of DNA is introduced and contains adjoining regions able to hybridize with the frayed regions of the pre-existing double-strand. Although the simplest example of branched DNA involves only three strands of DNA, complexes involving additional strands and multiple branches are also possible. [ 69 ]
These enzymes, along with accessory proteins, form a macromolecular machine which ensures accurate duplication of DNA sequences. Complementary base pairing takes place, forming a new double-stranded DNA molecule. This is known as semi-conservative replication since one strand of the new DNA molecule is from the 'parent' strand.
Nucleic acids consist of a chain of linked units called nucleotides. Each nucleotide consists of three subunits: a phosphate group and a sugar (ribose in the case of RNA, deoxyribose in DNA) make up the backbone of the nucleic acid strand, and attached to the sugar is one of a set of nucleobases.
In DNA double helix, the two strands of DNA are held together by hydrogen bonds. The nucleotides on one strand base pairs with the nucleotide on the other strand. The secondary structure is responsible for the shape that the nucleic acid assumes. The bases in the DNA are classified as purines and pyrimidines. The purines are adenine and guanine ...
The process of DNA replication is semiconservative; that is, the copy of the genome inherited by each daughter cell contains one original and one newly synthesized strand of DNA. [ 51 ] : 5.2 The rate of DNA replication in living cells was first measured as the rate of phage T4 DNA elongation in phage-infected E. coli and found to be ...
The 3′-end (three prime end) of a strand is so named due to it terminating at the hydroxyl group of the third carbon in the sugar-ring, and is known as the tail end. The 3′-hydroxyl is necessary in the synthesis of new nucleic acid molecules as it is ligated (joined) to the 5′-phosphate of a separate nucleotide, allowing the formation of ...
DNA is read by DNA polymerase in the 3′ to 5′ direction, meaning the new strand is synthesized in the 5' to 3' direction. Since the leading and lagging strand templates are oriented in opposite directions at the replication fork, a major issue is how to achieve synthesis of new lagging strand DNA, whose direction of synthesis is opposite to ...
Circular molecules of DNA, such as plasmids and typical mitochondrial genomes, consist of two strands of DNA called the heavy strand (or H-strand) and the light strand (or L-strand). The two strands have different masses due to different proportions of heavier nucleotides .