17) Genomics/ Sequencing Flashcards
What is the study of genetics? What is the study of genomics?
Genetics: Study of how a few genes determine phenotype
Genomics: Study of how lots of genes, and their architecture determine phenotype
What were some of the old methods of genome research?
1) Physical mapping and cytogenetics (Wilson and Steven)= Finding: Genes are on chromosomes, links phenotype to genetic unit
2) Genetic maps (Morgan)=
Finding: Genes don’t cluster by function in eukaryotes
Used visible traits and behaviours as phenotypes, no association of functionally related genes in Eukaryotic genomes BUT limited as could only be used in humans using disease or various simple physical traits
3) Molecular biology
New techniques in 1930s such as X-ray Crystallography
Used to explain in terms of molecules rather than organisms, organs or cells
Freed genetic mapping from having to use visible phenotypic mutants
Now: Phenotypes could be changes in molecules
Also revealed presence of introns + found DNA structure
4) Genome sequencing:
1) Sanger: Chain termination
2) Maxam-Gilbert sequencing
Both techniques worked by producing ‘nested fragments’ that were labelled then separated on gels
But couldn’t sequence entire genomes
What were the aims of the Human Genome Project? What did they do?
1) Create physical map of human genome
2) Genetic map of human genome
3) Nucleotide sequence of human genome
4) Free public access to all data generated
Moved away from EtBr strains and towards fluorescent dyes= All 4 sets of nested fragments (one for each base) could be run together on one lane of a gel
Laser scanned the dye and recorded the fluorescence and switched from gels to capillaries= Longer and more accurate separation
What is NGS?
Next Generation Sequencing
Able to sequence anything, including ancient but also cDNA
Switches to sequencing by synthesis
Allows: DNA to keep extending rather than stopping to read fragments= Really speeds it up
What are some of the findings of the Human Genome Project?
1) Gene distribution is not homogenous= Not the same everywhere as gene rich areas tend to be in euchromatin 2) Only 20,500 genes
3) Pseudogenes= Dead genes
4) Lots of transposable elements
