DNA sequencing

"Thinking Machine supercomputers and gene sequencers break down the strand in minutes..."

- Mr. DNA

The process of determining the precise order of nucleotides within a DNA molecule is called.

John Hammond used 24 automatic s to sequence the dinosaur DNA.

Distortion of the code
The processes of CpG methylation and cytosine deaminization must also be considered. A common regulatory device in eukaryotic DNA is the process of CpG methylation, where cytosine immediately preceding a guanine on the same strand is methylated. This acts as a molecular flag to control gene expression. Over time cytosine deamination can occur, in which a cytosine amine group is hydrolysed (replaced with a carbonyl oxygen). An unmethylated cytosine will read as uracil in any technique that relies on Watson-Crick base pairing. If the cytosine has been methylated then the product of deamination will be thymine, which again will be read as thymine. This issue can be addressed in a number of ways. If the DNA sample taken contains more than one copy of the DNA, a mixed signal of thymine and cytosine will suggest the occurrence of cytosine deamination. If the entire sample has suffered cytosine deamination at that point in the sequence, CpG tend to be found in "islands" rich in CpG, so TpG-rich islands or TpG/CpG rich islands would suggest cytosine deamination.