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Basic Biology - Molecules of life - RNA
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 RNA like DNA is constructed from nucleotides
RNA has various functions in a cell, e.g., mRNA and tRNA are functionally different types of RNA which are required for the two main steps in protein synthesis, transcription and translation, see diagram.
Structurally RNA differs from DNA. Instead of the pyrimidine thymine (T), it has an alternative uracil (U), which is not found in DNA. Because of this minor difference RNA do not form a double helix, instead usually they are single stranded, but may have complex spatial structure due to complementary links between the parts of the same strand (as for instance in tRNA).
RNA can bind complementary to a single strand of a DNA molecule,
even though T is replaced by U, so molecules like this
C-G-A-T-T-G-C-A-A-C-G-A-T-G-C DNA
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G-C-U-A-A-C-G-U-U-G-C-U-A-C-G RNA
are possible and in fact play an important role in life processes and in biotechnology.
There is a hypothesis that the first life on earth may have been RNA based. RNA can encode genetic information, is replicable, forms complex 3D structures and can also act as a catalyst for certain chemical reactions related to splicing
Next we will look at how genes encode proteins >>>
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