Space and time began about 13.7 billion years ago but it consisted almost exclusively of hydrogen until some stars grew sufficiently massive to create the heavier elements in gigantic explosions called supernovae.
The Sun formed about 4.6 billion...
Note that the carbon atoms are at the corners of the hexagon and pentagon and are not shown on the following diagrams.
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guanine
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thymine
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uracil
Nucleotides, the building blocks of nucleic acids, are composed of three molecules: at least one phosphate group, a five carbon sugar ( ribose or deoxyribose) and a nitrogenous nucleobase such as adenine. The whole structure shown is a nucleotide known as deoxyadenosine monophosphate.
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deoxyadenosine monophosphate.
A base pair is a unit consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix, and contribute to the folded structure of both DNA and RNA. Adenine and thymine (or uracil in RNA) are invariably paired as are guanine and cytosine. Each end of the base pair in the diagram is attached to a deoxyribose molecule that is part of the a DNA chain.
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DNA maintains a regular helical structure that dependents on its nucleotide sequence. The nature of this based-paired structure provides data redundancy and a backup copy of all genetic information encoded within double-stranded DNA. The diagram shows two base pairs connected to DNA chains (top and bottom)The haploid human genome (23 chromosomes) is estimated to be about 3.2 billion nucleobase pairs long and to contain 20,000–25,000 distinct protein-coding genes.
