* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Higher Biology Unit 1: DNA and the Genome 5
Maurice Wilkins wikipedia , lookup
Comparative genomic hybridization wikipedia , lookup
Exome sequencing wikipedia , lookup
Gel electrophoresis of nucleic acids wikipedia , lookup
DNA barcoding wikipedia , lookup
DNA sequencing wikipedia , lookup
History of molecular evolution wikipedia , lookup
Molecular cloning wikipedia , lookup
Molecular ecology wikipedia , lookup
Cre-Lox recombination wikipedia , lookup
Bisulfite sequencing wikipedia , lookup
Community fingerprinting wikipedia , lookup
Deoxyribozyme wikipedia , lookup
Nucleic acid analogue wikipedia , lookup
Whole genome sequencing wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Non-coding DNA wikipedia , lookup
Higher Biology Unit 1: DNA and the Genome 5. Genomic sequencing Notes Genomic sequencing Determining the sequence of the nucleotide base molecules all the way along an organism's DNA and then relating the information about the genes to their functions. Genomic sequencing involves the Genome shotgun approach which uses restriction endonucleases Restriction endonuclease: a type of enzyme that recognises a specific short sequence of DNA nucleotides called a restriction site on a DNA strand. It ‘cuts’ the DNA at this exact site all the way along the DNA strand at different point Take each fragment produced and sequence it to establish the order of its bases. Many of the fragments may overlap. Bioinformatics: The fusion of molecular biology, statistical analysis and computer technology. Has allowed genomics to make major scientific advances. Phylogenetics This is the study of evolutionary relatedness among different organisms. Uses information found from comparison of genome sequence data to deduce phylogenies (sequences of events involved in eth group’s evolution) and to construct phylogenetic trees. The evolutionary distance between the two groups can be found by counting the number of differences per unit length of DNA sequence between the two genomes. These distances can then be used to construct a phylogenetic tree. This shows the probable evolution of related groups of organisms and their phylogenetic patterns of divergence. Divergence Over time a group of closely related living things acquires its own set of mutations (such as nucleotide substitutions) which gradually alter its genome. This group may give rise to two groups that become more and more different from one another and eventually diverge. One they have diverged each group’s genome may undergo changes which are distinct to that group's genome. Therefore the more different the base sequences of two genomes are found to be, the more distantly related the two groups to which they belong and vice versa. Molecular clocks When genetic sequences for two related groups of organisms are compared, the number of nucleotide substitutions by which they differ is regarded as being proportional to the length of time that has elapsed since the groups diverged, i.e. since they shared a common ancestor. Therefore a molecule of nucleic acid (or a protein coded for by the nucleic acid) can be regarded as a molecular clock. A molecular clock can be given an actual time scale by plotting a graph the number of molecular differences it has evolved against a time scale based on fossil records. Molecular clocks are used as tools to try to date the origins of groups of living things and to determine the sequence in which they evolved. When a stretch of DNA does indeed behave like a molecular clock, it becomes a powerful tool for estimating the dates of lineage-splitting events. For example, imagine that a length of DNA found in two species differs by four bases (as shown below) and we know that this entire length of DNA changes at a rate of approximately one base per 25 million years. That means that the two DNA versions differ by 100 million years of evolution and that their common ancestor lived 50 million years ago. Since each lineage experienced its own evolution, the two species must have descended from a common ancestor that lived at least 50 million years ago. Personal genomics The branch of genomics involved in sequencing an individual's genome and analysing it using bioinformatics tools. In the near future it may be possible to sequence a person’s entire genome early in life and store that information for future consultation by doctors when required. Personalised medicine (pharmogenetics) 1 in 10 drugs (including the blood thinner warfarin) varies in effect depending on differences such as SNPs in the person's DNA profile. In future it may be possible to prescribe the most suitable drug and the correct dosage as indicated by personal genomic sequencing, reducing side effect and the increasing the effectiveness of the drug. It may also be possible to scan an individual's genome for predisposition to a disease and predict risk early enough to allow suitable action to be taken (for example, through appropriate drug treatment combined with a healthy lifestyle). Three domains of living things This evidence supports the idea that living things are made up of three domains. the bacteria (prokaryotes) the archaea (mostly prokaryotes that inhabit extreme environments such as hot springs and slat lakes) the eukaryotes (fungi, plants and animals)