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Frontiers of genetic
Question | Answer |
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How is the genome sequencing performed? | use bases that terminate polymerisation because they lack a 3' OH. |
How does Fluorescent dideoxy-NTPs work? | label 4 dideoxynucleotides with 4 different coloured fluorescent dyes amd run them in 1-D capillary. Have camera watching colour chnage. |
How does next generation sequencing work? | get genome, shot gun sequence, fragmentation, sequence at same time, millions of short sequences, use technologies such as illumina on a chip. |
Define exome sequencing: | only exons or protein-coding genes are sequences. Quicker and cheaper, isolation methods are based on libraries of 100,000s of oligonucleotide sequences that allow exon DNA to be isolated. |
What is TCGA? | The cancer genome atlas. Comprehensive database of key genomic changes in types of cancer based on tissue samples of 11,000 patients. |
What is ENCODE? | Encyclopedia of DNA Elements project, aim to identify all functional elements in human genome, not just sequence. |
What does the FDA now allow 23andme to do? | 2017 - approves selling tests for genetic ridk for 10 diseases e.g. Alzheimer's, Parkinson's etc. 2018 - approves tests for 3 allele of BRCA genes (well known risk gene for cancers e.g. breast, ovarian, prostate). |
What did scientists discover about Nicholas Volker? | He had a severe case of Crohn's disease, Doc used exome sequencing. 16,000 single nucleotide variants compared with reference sequence. 70 homozygous variants that affected protein sequence...eventually 1 variant left - mutation in XIAP. |
What is a XIAP mutation? | X-linked Inhibitor of Apoptosis - G-->A. Cysteine --> Tyrosine. Variant wasn't found in search of 2000 human control sequences or in orthologous genes from other species. |
How was Nicholas treated? | hematopoietic progenitor cell transplant - his own hematopoietic stem cells were destroyed with chemo and then replaced by an infusion of cord blood - to reestablish his immune system. |
Define gene therapy: | use of recombinant DNA to treat a disease or disorder by altering the genetic makeup of the patient's cells. |
What are some considerations to take into account for gene therapy? | - mechanism for introducing DNA - viral vs non-viral approaches. - targetting location - random position in the genome; known locus with appropriate expression; the locus of the gene itself. |
What is a new treatment for haemophiliacs? | Adenovirus-Associated Virus for gene therapy. Single infusion of AAVFIX virus. Expression of FIX at 2 to 11% of normal levels was observed in all haemophiliacs. 4/6 discontinued prophylaxis and remained free of spontaneous hemorrhage. |
What are advantages of gene therapy? | doesn't produce a big immune response; can infect dividing and non-dividing cells; DNA can persist in cell for a long time, but doesn't insert randomly into genome (and cause mutations). Disadvantage: gene size limited to ~5kb. |