The Genetic Code

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The Genetic Code: The sequence of DNA bases determines the sequence of amino acids which determines the proteins made.

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Recap of DNA Bases:

The four nitrogen-containing bases in DNA are:

Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T)

Base Pairing Rules:

Adenine (A) always pairs with Thymine (T).
Cytosine (C) always pairs with Guanine (G).

Hydrogen Bonds:

A and T are joined by 2 hydrogen bonds.
C and G are joined by 3 hydrogen bonds.

What is the Genetic Code?

Genes are made up of long sequences of DNA bases.
A gene causes a specific sequence of amino acids to be arranged to form a protein.
The genetic code ensures that the correct amino acids are assembled in the correct order to form the protein.

How the Genetic Code Works:

The code operates as a sequence of 3 DNA bases, called a triplet or codon.
Each triplet codes for a specific amino acid.
Example:
- The triplet CAA codes for the amino acid valine.
- The triplet CGA codes for the amino acid alanine.
Many triplets together form a gene.

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Analogy: The Genetic Code and Language

The 4 DNA bases (A, T, C, G) are like the letters of the alphabet.
Each triplet (codon) forms a word.
A sequence of triplets forms a gene, which is like a paragraph giving instructions for how to make a protein.
All the genes in a cell (the genome) form the book of life for that cell.

Non-Coding DNA

Up to 97% of DNA in human cells does not code for the production of proteins. This is called non-coding DNA.
Non-coding DNA was once called 'junk' DNA because its purpose was unknown.
Scientists now know that non-coding DNA plays important roles, such as regulating the expression of genes (acting like a switch to turn genes 'on' or 'off').

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