Higher Biology Genomic Sequencing Mr G R Davidson

Genomics All the genes in an organism are collectively known as the genome. Genomics is the study of genomes. New technology has allowed us to determine the sequence of nucleotides in an organism’s DNA. Tuesday, 18 September 2018 G R Davidson

Genomics It is done by comparing data and statistical analysis and is known as bioinformatics. An enzyme called restriction endonuclease can be used to recognise very specific short DNA sequences called restriction sites. The enzyme then ‘cuts’ the DNA at precisely these points. Tuesday, 18 September 2018 G R Davidson

Genomics Different restriction enzymes are responsible for cutting the DNA at different nucleotide sequences. If we know the DNA sequence the enzyme uses, we can then use a number of different enzymes to cut up the DNA into fragments. Tuesday, 18 September 2018 G R Davidson

Genomics This information can then be analysed by computer and the complete sequence can be worked out. The human genome project was set up to discover the sequence of the human genome and this was successfully completed in 2003. As well as humans, other species important to humans were also prioritised, e.g. crop plants, crop pests, disease-causing organisms, etc.. Tuesday, 18 September 2018 G R Davidson

Genomics Some of these organisms may contain gene sequences the same as humans which can then be researched a lot easier. A person’s individual genome could also be used to personalise treatment or medicines. This is called pharmacogenetics. Tuesday, 18 September 2018 G R Davidson

Phylogenetics Phylogenetics is the study of how organisms are related in evolutionary terms. Genomic sequence data is used to construct phylogenetic trees. Tuesday, 18 September 2018 G R Davidson

Phylogenetics Organisms closely related have genomes very similar to each other. Gradually, over long periods of time, mutations occur which causes the two species to diverge. The more of these means the species are more distantly related. Tuesday, 18 September 2018 G R Davidson

Phylogenetic Tree J K The current species L Common ancestor M N Timescale in millions of years BP (before present) Tuesday, 18 September 2018 G R Davidson

Phylogenetics Because of these mutations, groups become genetically different. Therefore, the more mutations there are, the more distant the relationship is likely to be. This principle is known as the molecular clock. Tuesday, 18 September 2018 G R Davidson

Phylogenetics This has been used to identify 3 distinct groups of living things that originated from a common ancestor. Bacteria Archaea (prokaryotes which can survive in extreme conditions such as deep sea, thermal springs, etc.. Eukaryotes (animals, plants & fungi) Tuesday, 18 September 2018 G R Davidson

Phylogenetics Bacteria Archaea Common ancestor Eukaryotes Tuesday, 18 September 2018 G R Davidson

Phylogenetics Fossil dating has also been used along with genome sequencing to produce a timeline of evolution, e.g. Life on Earth Approx. 4,000,000,000 years ago TIME Evolution of cells Approx. 3,000,000,000 years ago Eukaryotes evolved Approx. 1,800,000,000 years ago Multicellular organisms evolved Approx. 1,200,000,000 years ago Animals evolved Approx. 550,000,000 years ago Vertebrates evolved Approx. 480,000,000 years ago Land plants evolved Approx. 435,000,000 years ago Tuesday, 18 September 2018 G R Davidson

Personal Genomics We now have the ability to sequence an individual’s genome and analyse it. This could be used to determine the risk factor involved in a person developing certain conditions or illnesses. This is where pharmacogenetics comes in. Tuesday, 18 September 2018 G R Davidson

Personal Genomics This process does raise one or two ethical issues. Who should have access to this information and why. Genetic discrimination could arise. These are issues which need to be addressed before this procedure becomes cheap enough to be carried out on a regular basis. Tuesday, 18 September 2018 G R Davidson