Studying Whole Genomes

It's missing notes on Electrophoresis and DNA probes.  I'll put them is ASAP.

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  • Created by: Arianne
  • Created on: 01-02-13 11:25

Understanding and Manipulating DNA

Uses of DNA

  • DNA profiling (genetic fingerprinting)
  • Genomic sequencing and comparative genome mapping
  • Genetic engineering
  • Gene therapy

All DNA contains sections called genes, which code for polypeptides and protiens.  Coding DNA only forma 1.5% of DNA in humans.  Much DNA is non-coding, formerly known as junk, but is now known to have regulatory functions.

Genomics - the study of genomes - wants to map the whole genome of organisms; comparing genes and DNA sequences to understand the relationship between genes and health, behaviour and evolutionary roles between organisms.

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Sequencing Genomes - the basics.

The sequencing reaction can only operate on a length of DNA of around 750 base pairs.  The genome must be broken up and sequenced in sections.

  • Genomes are mapped to identify where on the chromasome they have come from; information that is already known is used (eg using microsatellites).
  • Samples of the genome are sheared (mechanically broken) into sections of around 100,000 base pairs.  Sometimes known as the "shotgun" approach.
  • The sections are then placed into seperate Bacterial Artificial Chromosomes (BACs) and transferred to E. coli cells.
  • This produces many copies of the sections, forming clone libraries.
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Sequencing BAC Sections

In order to sequence BACs:

  • cells containing specific BACs are cultured.  DNA is extracted and restriction enzymes  are used to cut it into smalled fragments.
  • Fragments are separated using electrophoresis.
  • Each fragment is processed using an automated process.
  • Computer programmes compare overlapping regions from the cuts made by different restriction enzymes in order to reassemble the whole sequence.
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