Biotechnology and its Applications

In some cases, recombinant DNA can have deleterious effects even if it is not expressed. 

Enhancers are sites on the DNA helix that are bound to by activators in order to loop the DNA bringing a specific promoter to the initiation complex. Enhancers are much more common in eukaryotes than prokaryotes.

RT-PCR measures the absolute abundance of total or nuclear RNA levels, which may however differ from transcription rates.

The desired DNA fragment is inserted into a vector, usually a plasmid, for transfer to the receiving chromosome. Plasmids are circular DNA molecules found in the cytoplasm of bacteria that bond with the desired DNA fragment with the help of the joining enzyme, DNA ligase, to create the resulting recombinant DNA.

Sequencing by hybridization is a non-enzymatic method that uses a DNA microarray. A single pool of DNA whose sequence is to be determined, is fluorescently labeled and hybridized to an array containing known sequences. Strong hybridization signals from a given spot on the array identify its sequence in the DNA being sequenced.

Alternative splicing can be analysed with a splicing array or with a tiling array. Epistatic interactions can be investigated by synthetic genetic array analysis.

SNP array is a type of DNA microarray which is used to detect polymorphisms within a population. A single nucleotide polymorphism (SNP), a variation at a single site in DNA, is the most frequent type of variation in the genome.

Probe-target hybridization is usually detected and quantified by detection of fluorophore, silver, or chemiluminescence-labeled targets to determine relative abundance of nucleic acid sequences in the target.

Microsatellites within introns also influence phenotype. For example, a GAA triplet expansion in the first intron of the X25 gene appears to interfere with transcription, and causes Friedreich Ataxia (Bidichandani 1998).

Satellite DNA are organized as large clusters upto 100 million base pairs in the heterochromatic region of chromosomes near centromeres & telomeres, these are also found abundantly on Y chromosomes.

Many noncoding DNA sequences have important biological functions as indicated by comparative genomics studies that report some regions of noncoding DNA that are highly conserved, sometimes on time-scales representing hundreds of millions of years, implying that these noncoding regions are under strong evolutionary pressure and positive selection. 

If a chromosome segment gets inserted in interstitial position of a non-homologous chromosome, it is known as shift translocation. In humans, it is invariably associated with myelogenous leukemia.

Restriction enzymes are made up of proteins. The main purpose of restriction enzymes is to make new copies of DNA and analyze it. Agarose gel electrophoresis is the main technique which makes use of the restriction enzymes. When the solution containing DNA molecules and restriction enzymes is placed in the gel, an electric current is passed through it which cuts the DNA into fine small fragments.  

Polony sequencing is an inexpensive but highly accurate multiplex sequencing technique that can be used to read millions of immobilized DNA sequences in parallel.

An inducible gene is a gene whose expression is either responsive to environmental change or dependent on the position in the cell cycle.