Colour coding for molecular structures





Nucleic acid bases:purines and pyrimidines

Nucleotides and nucleosides






Nucleic Acids


What is the difference between DNA, chromosomes, genes etc ?

All genetic material is made of DNA, which is a very long molecule so that it must be "packed" properly so that it fits into the nucleus. There are special proteins called histones that are responsible for just that. The basic aminoacids in the histones bind to the negative phosphate groups in DNA, i order to reduce their mutual repulsions. This allows the 5 billions of base pairs that make up human DNA to fit into a nucleus that has a diameter of 10 microns.

The resulting structure is called chromatin, which turns into chromosomes (from the Greek: chromos-colour; soma-body) just before cell division. They receive this name because they are easily stained using appropriate dyes, so that they can be seen on the optical microscope. That means that each chromosome is a separate DNA molecule.

Genes are pieces of DNA that code for a specific trait.

Humans have 46 DNA molecules (chromosomes).

Nucleic acids, DNA em RNA, are polymers of nucleotides, e.g., they are macromolecules (very large molecules) made of small repeating units (nucleotides).

What are nucleotides?

Nucleotides are the units out of which nucleic acids are constructed.

They consist of of a base, a sugar, and a phosphate residue.



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