n order to study this pathogen, you are tasked with determining the genome sequence of the organism. The DNA is easy to extract, and initial analysis suggests that the genome is approximately 5 Mb in length. Which two sequencing technologies would you use to sequence the genome? Describe in your answer the molecular mechanisms of both your chosen technologies and provide ONE advantage and ONE disadvantage of each technology. (5 marks)

To sequence the genome of the organism, two sequencing technologies that could be used are Sanger Sequencing and Next-Generation Sequencing (NGS).

1. Sanger Sequencing: This method, also known as chain termination sequencing, involves the use of dideoxynucleotides (ddNTPs) in addition to the normal nucleotides found in DNA. These ddNTPs act as chain terminators, as they lack the 3'-OH group required for forming the phosphodiester bond for chain elongation. The terminated sequences are then separated by size using capillary electrophoresis, and the sequence is read from the smallest to the largest fragment.

   Advantage: Sanger sequencing is highly accurate over longer reads (up to 1000 base pairs), which makes it ideal for sequencing smaller genomes or for validating the results of NGS.

   Disadvantage: It is time-consuming and expensive, especially for larger genomes.

2. Next-Generation Sequencing (NGS): This is a high-throughput method that allows for the simultaneous sequencing of millions of fragments. There are several types of NGS, but a common method is sequencing by synthesis. This involves the synthesis of a complementary strand to the template strand, with each incorporated nucleotide being identified by its attached fluorescent label. The signal is detected each time a nucleotide is incorporated.

   Advantage: NGS can generate a large amount of data quickly and is therefore more cost-effective for sequencing larger genomes.

   Disadvantage: It has a higher error rate than Sanger sequencing and shorter read lengths, which can make the assembly of the genome more challenging.

Both methods would be useful for sequencing the 5 Mb genome, with Sanger sequencing being used to validate the results of the NGS.