21.2 DNA sequencing and analysis

• What is a genome?

  genes or genetic material present in a cell or organism
• Give two reasons why new DNA sequencing techniques have improved upon old methods

  Quicker, cheaper
• In order to use the Sanger sequencing method, apart from the DNA sample to be sequenced, what are the four other chemicals needed?

  Taq DNA polymerase, a primer, normal nucleotides, chain terminator nucleotides (ddNTPs)
• How is a terminator base different from a normal nucleotide?

  Has a hydrogen instead of hydroxyl group on C3 of the deoxyribose sugar
• Why would the addition of the terminator base stop further extension of the DNA strand in DNA sequencing?

  Terminator bases do not have hydroxyl group on C3 of deoxyribose, therefore cannot form phosphodiester bonds with the next nucleotide
• How are the terminator bases altered in order for the sequence of nucleotide to be seen or detected?

  Has a coloured fluorescent tag - 4 different colours for different bases
• What is the first step in sequencing a whole genome?

  Cut the genome into smaller fragments (and clone into BACs to make a clone library)
• How are the DNA fragments separated and read in DNA sequencing?

  Gel electrophoresis in minute capillary tubes --> separate DNA fragments by size --> They can be read when passing through a laser that reads the colour as they pass through
• Briefly describe how next-generation sequencing works.

  Automated, high-throughput sequencing process: millions of DNA fragments are attached onto a surface and sequenced as clusters at the same time