Question

Relate the following assays to DNA annealing:

• PCR

• DNA sequencing

• Southern blotting

• microarray analysis

Answer 1

PCR polymerase chain reaction is to make copies of a section of DNA. First developed in 1980s by Karry Mullis. It is a common tool in biological and research fields. There are three main steps for PCR :

Denaturing, Annealing, extending

In Annealing stage reaction is cooled to 50-65 degree Celsius. This enables primer to attach to the single stranded template DNA by hydrogen bonding.

DNA sequencing : by PCR DNA can be sequenced by millions or billions times. DNA sequencing is the process of determining the sequence of nucleotides in a piece of DNA . To obtain multiple DNA copies pcr is used. If DNA sample is too small we should make multiple copies as our interest. Therefore, PCR amplification gave some additional advantages. For the investigation of crime scene crime samples are used to amplify the DNA before DNA sequencing. Reannealing of primers gives short chains to long chains of DNA.

Souther blotting:it is a method developed by E. M Southern for detection of DNA that has been electrophoretically separated immobilised by blotting on nitrocellulose or other type of nylon membrane followed by hybridization with labelled nucleic aci probes.

Microarray analysis:it is a simple concept dot blot + northern blotting. It is a method that containing microchips arrays of probes for the large-scale interrogation of gene expression.it also used to study the extent which certain genes are turned on or of in cells or tissues. Today DNA microarray are used for diagnostic tests. To identify disease DNA microarray are used.