Genome sequencing

genomics

1. GENOME SEQUENCING Subhananthini Jeyamurugan, 18py17, M.Sc., microbiology. Ayya nadar Janaki ammal college, Sivakasi.

2. GENOME SEQUENCING : GENOME : The complete set of genes of an organism. SEQUENCING : Arrangement of nucleotide base pairs.

3. HUMAN GENOME PROJECT(HGP ): It is a project to map and sequence the 3 billion nucleotides contained in the genome and to identify all the genes present in it.

4. The HGP was officially launched in US in 1990,15 years effort sponsored by the NATIONAL INSTITUTES OF HEALTH AND DEPARTMENT OF ENERGY . Sequencing centers in china france, germany , japan and UK.

5. HIERARCHIAL SHOT GUN SEQUENCING: The HUMAN GENOME PROJECT used hierarchial shot gun assembly to sequence the human genome.

6. REQUIREMENTS : DNA(from blood sample). Restriction endonucleases.(EcoR1) BAC(Bacterial artificial chromosome.) Eschierichia coli

7. BAC (Bacterial Artificial Chromosome ): Artificial chromosome it is a vector that can carry larger DNA fragments.(300Kb) BAC also a vector to artificially carry DNA into the cell of a bacterium Escherichia coli to make a BAC clone .

8. STEPS INVOLVED IN HIERARCHIAL SEQUENCING: DNA isolated from blood sample from unknown person. Digested with restriction endonucleases(BAMH1,ECOR1) pieces between 100kb-200kb length were inserted in BAC. The recombinant BAC collection is known as BAC library . BAC library stored in freezer condition. Whenever it was needed that was used.

9. BAC inserting method: Each BAC insert had to be assigned to a specific location in human genome. one way to accomplish this task is to match unique landmark in the human genome with the same landmark in an insert. there are 2 landmark: protein coding gene. Recombinant DNA technology.

10. LANDMARK: Any short piece of DNA with a unique sequence and a known chromosomal location can serve as a landmark. thousands of such Short (200-500bp) unique sequence called sequence tagged sites(STS).

11. BAC Insert method: BAC inserts were also ordered by restriction fingerprint analysis as follows. BAC inserts were digested with a restriction endonucleas and the resulting fragments separated by gel electrophoresis. If electrophoretic patterns produced by different BAC clones had bands in common then the inserts were likely to contain overlapping fragments.

12. DNA from each selected BAC clones was purified, subjected to shotgun sequencing and contigs assembled. A single capillary DNA sequencer handled about 40000 fragments in a day(1990). In 1999 the sequencing center at MIT sequenced and processed about 1,20,000 fragments per day most routine work was done robotically.

13. HUMAN GENOME : A. The human genome has a total of 3164.7 million nucleotide bases. B. The total number of genes is estimated to be 30,000. C. The functions of over 50% of discovered genes are not known. D. The average gene consists of 3000 bases. However, the largest gene is dystrophin made of 2.4 million bases.

14. E. A large portion of the human genome is made of repeated sequences. F. Chromosome 1 has the maximum number of genes (2968) and the Y has the least (231).

15. The Human Genome Project Advantages: Predict and prevent diseases:  By knowing which genes predispose people to particular conditions, doctors will be able to predict which people are likely to suffer from a particular disease and  offer a preventive course of action, which may involve medical treatment or lifestyle changes. Furthermore, cures could be found for genetic diseases like cystic fibrosis or sickle cell anaemia. .

16. Improved medicine: Personalized medicines can be developed based on the way our individual bodies react to the disease and the treatments, which will be more effective because the medicines will be tailored for our specific medical needs.

17. Accurate diagnoses : Doctors can develop more accurate diagnostic techniques for certain conditions which are difficult to diagnose at an early stage Improve forensic science : Genetic fingerprinting helps to match a suspect to the biological material found at a crime scene. In the future it could be possible to figure out what a suspect looks like from DNA found at a crime scene e.g. their eye, hair and skin colour .

18. Disadvantages : Increased stress: People could be diagnosed with illnesses that they are suspectible to develop in the future and spend their life worrying about it even before they get it. Geneism : People with genetic problems could be under pressure not to have children as a threat of passing on their faulty genes onto the next generation.

19. Benefits: The potential benefit of a comprehensive sequencing effort was highlighted by the isolation of disease-linked genes such as Huntington's disease, Cystic Fibrosis, and the most common breast-cancer-associated gene, BRCA1. But most common human diseases are genomic - "polygenic" diseases caused by multiple genes spread diffusely throughout the human genome. Cancer and mental illnesses are examples of genomic diseases.

20. Thank you…