DNA Sequencing
- DNA sequencing allows for the nucleotide base sequence of an organism's genetic material to be identified and recorded
- Most methods for sequencing DNA involve the use of chain-terminating dideoxynucleotides
- The dideoxy chain-termination method was developed by Frederick Sanger in 1977
- The chain-termination method uses modified nucleotides called dideoxynucleotides
- Dideoxynucleotides have a slightly different structure to standard nucleotides
- They lack the 3’-hydroxyl group so cannot form a covalent bond with the next nucleotide to be incorporated by DNA polymerase
- Dideoxynucleotides prevent elongation of the nucleotide chain, which therefore terminates
- Advances in technology have enabled the development of rapid high-throughput sequencing methods which allow scientists to sequence the genomes of organisms rapidly
- Most sequencing methods used are now automated rather than requiring manual interpretation
- The data obtained from sequencing can be entered into computers with specialized programmes that compare the base sequences of different organisms
Exam Tip
The fine details of the various techniques of DNA sequencing are not required for the AP Exam
