Science Module B5- Growth And Development

DNA Structure

How many dna bases are there? What are the letter codes for the bases and which letter code do they pair to?

(http://www.biojobblog.com/uploads/image/dna_500.jpg)

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· Each nucleotide contains a small molecule called a base. DNA has 4 different bases: ADENINE (A), CYTOSINE (C), GUANINE (G), THYMINE (T).

· The 2 strands are held together by the bases, which always pair up in the same way-its always A&T, C&G. This is simply called base pairing.

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How Does DNA Control The Production Of Proteins In A Cell?

(http://www.myproteinnutrition.com/images/amino_acid_protein_1.jpg)

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Cells make proteins by joining amino acids together in a particular order.
Its the order of the bases in a gene that tells the cell in what order to put the amino acids together.
Each set of three bases (called a triplet) codes for ONE amino acid.
DNA also determines which genes are switched on or off- and so which protein the cell produces. For Example: Keratin, which in turn determines what type of cell it is (skin cell).

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