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How does DNA code for proteins?

What is DNA? DNA is the chemical used to store genetic information (inherited traits and characteristics) in the body.  The shape of DNA is a double helix (two complementary chains, interwoven).  Every chain has four seperate components; 'bases' or 'nucleotides'.  The bases are Adenine (A), Thyamine (T), Cytosine (C) and Guanine (G).  Certain bases on one chain can only pair with certain bases on the other chain: A can only pair with T (A-T), C only with G (C-G).  The order in which these base pairs are linked together determines the DNA sequence.  Sequencing enables massive amounts of information to be stored simply in a small space.

Proteins? They are structures made from amino acids that are key to functioning in all cells in the body.

How do you get from DNA to proteins? Unique sequences of DNA are called genes.  Genes can be read to form proteins.  This is done by two main processes; transcription and translation.  

What is transcription? It is the synthesis of RNA from a DNA sequence.

What is RNA? RNA is a chemical used to transfer genetic material inside a cell.  It is a very similar compound to DNA; it has just one base different (Uracil instead of Thyamine).  Like Thyamine in a DNA strand, Uracil can only pair with Adenine (A-U) in a RNA strand.  There are many types of RNA.  Messenger RNA (mRNA) and Transfer RNA (tRNA) are used to help make proteins.  RNA is synthesised in the nucleus of the cell.

How does transcription work? One of the DNA strands is used as a template (remember two strands bound together to form a double helix).  The strands of DNA are unzipped during transcritpion and then zipped back up again afterwards.  RNA uses the DNA template to match its bases corresponding to the DNA ones, to form a mRNA chain.  (You could think of transcription like in music, where you transcribe a piece/sound of music into a notation on page, or in linguistics where you take sign language and write it down in text).

And translation? This is the process in which a mRNA  strand is read in order to form a sequence of amino acids (a polypeptide chain).  The mRNA strand is transported out of the nucleus and into the cytoplasm of the cell. Translation in the cytoplasm prevents damage to the DNA in the nucleus. The process occurs with the help of a ribosome.

How exactly does it work? A certain three bases of a mRNA chain forms a 'codon'.  To code for an amino acid, the codon must be read by tRNA.  Three complementary tRNA bases is called an 'anti-codon'. Codons match with anti-codons. Certain anti-codons have certain amino acids attached to them.  For example UAC has tyrosine.  So when multiple mRNA codons complement with multiple tRNA anti-codons, the amino acids attached can bind together to form an amino acid sequence.  The ribosome facilitates this process. (You could think of translation like studying a foreign language, translating French into English).

How do you form a protein? A chain of amino acids or 'polypeptide chain' can be further shaped and packaged in the rough endoplasmic reticulum of a cell to form a protein.

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