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Pseudogenes are nonfunctional segments of DNA that resemble functional genes.Pseudogenes can be formed from both protein-coding genes and non-coding genes. In the case of protein-coding genes, most pseudogenes arise as superfluous copies of functional genes, either directly by gene duplication or indirectly by reverse transcription of an mRNA transcript.
The nonfunctional DNA in bacterial genomes is mostly located in the intergenic fraction of non-coding DNA but in eukaryotic genomes it may also be found within introns. There are many examples of functional DNA elements in non-coding DNA, and it is erroneous to equate non-coding DNA with junk DNA.
Junk DNA (non-functional DNA) is a DNA sequence that has no known biological function. [ 1 ] [ 2 ] Most organisms have some junk DNA in their genomes —mostly pseudogenes and fragments of transposons and viruses—but it is possible that some organisms have substantial amounts of junk DNA.
The onion test is a way of assessing the validity of an argument for a functional role for junk DNA.It relates to the paradox that would emerge if the majority of eukaryotic non-coding DNA were assumed to be functional and the difficulty of reconciling that assumption with the diversity in genome sizes among species. [1]
For example, the standard protocols for DNA fingerprinting involve PCR analysis of panels of more than a dozen VNTRs. RFLP is still used in marker-assisted selection. Terminal restriction fragment length polymorphism (TRFLP or sometimes T-RFLP) is a technique initially developed for characterizing bacterial communities in mixed-species samples.
A restriction fragment is a DNA fragment resulting from the cutting of a DNA strand by a restriction enzyme (restriction endonucleases), a process called restriction. [1] Each restriction enzyme is highly specific, recognising a particular short DNA sequence, or restriction site, and cutting both DNA strands at specific points within this site.
Example of an approximately 40,000 probe spotted oligo microarray with enlarged inset to show detail. Microarray analysis techniques are used in interpreting the data generated from experiments on DNA (Gene chip analysis), RNA, and protein microarrays, which allow researchers to investigate the expression state of a large number of genes – in many cases, an organism's entire genome – in a ...
Since DNA is interpreted in groups of three nucleotides (codons), a DNA strand has three distinct reading frames. [15] The double helix of a DNA molecule has two anti-parallel strands; with the two strands having three reading frames each, there are six possible frame translations. [15] Example of a six-frame translation.