Uses of Genome Sequencing (SL IB Biology)

Genome sequencing

• DNA sequencing allows for the base sequence of an organism's genome to be identified and recorded
• Sequencing methods are continuously advancing to become faster and cheaper
  • Advances in technology have allowed scientists to rapidly sequence the genomes of organisms
  • Most sequencing methods used are now automated
• Newer methods of genome sequencing are known as next-generation sequencing (NGS) techniques
• The data obtained from sequencing can be entered into computers with specialised programmes that can analyse the information for purposes such as:
  • Determining evolutionary relationships
  • Personalised medicine

Genome sequencing & evolutionary relationships

• Phylogenetics is the classification of species based on their evolutionary origins and relationships
  • This means that organisms are grouped together on the basis of shared common ancestry rather than, e.g. similarities in appearance
• Advances in sequencing technology have allowed scientists to understand the true phylogeny of taxa
  • Note that this technology is especially useful for comparison with an extinct species (using ancient DNA) or when distinguishing between species that are very physically similar
• Three types of sequence data are used to investigate evolutionary relationships
  • DNA
  • mRNA
  • Amino acids (of a protein)
• For all types of sequence data it can be said that the more similar the sequences, the more closely related the species are
  • Two groups of organisms with very similar sequences will have separated into separate species more recently than two groups with less similarity in their sequences
  • Species that have been separated for longer have had a greater amount of time to accumulate mutations and changes to their DNA, mRNA and amino acid sequences
• Scientists will choose specific proteins or sections of the genome for comparison between organisms
  • Looking at multiple proteins or multiple regions of the genome will allow for a more accurate estimate of evolutionary relatedness
  • Note the protein used needs to be present in a wide range of organisms and show sufficient variation between species
    • Cytochrome c is often used as it is an integral protein in aerobic respiration, which occurs in many organisms
• Sequence analysis and comparison can be used to create phylogenetic trees that show the evolutionary relationships between species

Primate phylogenetic tree diagram

Genome sequence data can be used to produce phylogenetic trees that accurately show the relationships between species

Genome sequencing & personalised medicine

• Information gathered from genome sequencing projects like the Human Genome Project can be used to develop genomic medicine, which uses information about the genes to design medical treatments
  • The Human Genome Project involved the sequencing of the entire human genome
• The information gained during the Human Genome Project is stored in databases, within which genes that code for certain proteins can be found and analysed
• Knowing the sequence and structure of proteins involved in disease allows the development of drugs that target specific proteins
  • E.g. if an enzyme is involved with disease, a drug that acts as an enzyme inhibitor can be developed
  • Targeted treatments can mean fewer unpleasant side-effects for patients
• By combining information about the genome with other clinical and diagnostic information, patterns can be identified that can help to determine an individual's risk of developing disease
  • Genetic screening allows individuals with a high chance of developing specific diseases to be identified and means that preventative measures can be taken, e.g.
    • Certain genetic mutations are known to increase the risk of an individual developing breast cancer, so those who know that they have such a mutation can have surgery in advance to reduce their risk
    • An individual may be able to make certain life choices regarding diet and lifestyle based on knowledge of their genetic risk of cancers and heart disease
• Doctors can also use an individual's genome to work out how well they might respond to specific treatments, allowing treatments to be selected on the basis of an individual's genotype