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DNA

>> Parts of this equation/concept include:

A -	Determining Complimentary Chains
B -	Determining mRNA Chains

The two chains of DNA are held together by hydrogen bonding between the nitrogen base part of the nucleotide. The interaction between bases is specific—the adenine base hydrogen bonds to the thymine base, and the cytosine base hydrogen bonds to the guanine base. The complimentary chain consists of the opposite base. The first letter of the name of the base is used to represent that nucleotide segment.

>> Example 1

What sequence is complimentary to CCTAGTCATT? Write the new sequence as if it were base-pairing with this sequence.

Solution:

Replace each C with its complement G and C with G. Also replace T with A and A with T. Thus the complementary sequence is

GGATCAGTAA

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DNA is copied to mRNA through the process of transcription. During transcription, the DNA double helix "unzips," and one chain is copied. The system of copying a DNA sequence to an mRNA sequence is the same as the system of copying one DNA seqnence to another DNA sequence, except that in RNA uracil is substituted for thymine to base pair with adenine.

>> Example 2

What mRNA sequence forms from the DNA sequence CTTAAGCGTC? Write the mRNA sequence as if it were base-pairing with the DNA sequence.

Solution:

Replace C with G, T with A, A with U, and G with C. Therefore, the mRNA sequence is GAAUUCGCAG.

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