Molecular Biology Techniques

Modern molecular biology techniques can be used in a variety of ways, including:

  • Sequencing:  Determining the base sequence of a gene of interest for use in screening or drug development
  • DNA profiling:  Comparing the DNA sequences of individuals for use in identification (such as for forensic investigations or paternity testing)
  • Gene Transfer:  Recombining DNA from different sources to create transgenic organisms with new traits / characteristics
  • Screening:  Gene probes can be used to identify mutant alleles that cause disease conditions, enabling more effective treatment

All four of these techniques require large amounts of DNA, which can be amplified using the polymerase chain reaction

DNA Amplification  (PCR)

PCR is a way of producing large quantites of a specific target sequence of DNA

It is useful when only a small amount of DNA is avaliable for testing 

  • E.g. crime scene samples of blood, semen, tissue, hair, etc.

PCR occurs in a thermal cycler and involves a repeat procedure of 3 steps:

1.  Denaturation:  DNA sample is heated to separate it into two strands

2.  Annealing:  DNA primers attach to opposite ends of the target sequence

3.  Elongation:  A heat-tolerant DNA polymerase (Taq) copies the strands 

One cycle of PCR yields two identical copies of the DNA sequence

  • A standard reaction of 30 cycles would yield 1,073,741,826 copies of DNA (230)

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