Bioinformatics glossary - N

N-terminus
It is the start of a amino acid chain terminated by an amine group (-NH2).

Naked DNA
Pure, isolated DNA devoid of any proteins that may bind to it.

NCEs (New Chemical Entity)
Compounds identified as potential drugs that are sent from research and development into clinical trials to determine their suitability.

Necrosis
Localized and premature death of cells in an organ or tissue due to disease or injury.

Nested PCR
The second round amplification of an already PCR-amplified sequence using a new pair of primers which are internal to the original primers. Typically done when a single PCR reaction generates insufficient amounts of product.

Neural net
A neural net is an interconnected assembly of simple processing elements, units or nodes, whose functionality is loosely based on the animal brain. The processing ability of the network is stored in the inter-unit connection strengths, or weights, obtained by a process of adaptation to, or learning from, a set of training patterns. Neural nets are used in bioinformatics to map data and make predictions, such as taking a multiple alignment of a protein family as a training set in order to identify novel members of the family from their sequence data alone.

Needleman-Wunsch algorithm
This global sequence alignment method – the first to apply dynamic programming techniques to biological sequence analysis – explores all possible alignments and choose the best one (the optimal global alignment). It does this by reading in a scoring matrix and a gap penalty (penalties) that contains values for every possible residue or nucleotide match and summing the matches taken from the scoring matrix.

Neighbour Joining method
Neighbour joining is a bottom-up (agglomerative) clustering method for the creation of phylogenetic trees, created by Naruya Saitou and Masatoshi Nei. It is usually used for trees based on DNA or protein sequence data, and the algorithm requires knowledge of the distance between each pair of taxa (e.g., species or sequences) to form the tree.

Next generation sequencing
Next generation sequencing or high-throughput sequencing technologies parallelise the sequencing process, producing thousands or millions of sequences at once.

NCBI-Blast2
BLAST stands for Basic Local Alignment Search Tool.The emphasis of this tool is to find regions of sequence similarity, which will yield functional and evolutionary clues about the structure and function of your novel sequence.

Nonsense mutation
A point mutation in which a codon specific for an amino-acid is converted into a nonsense codon.

Northern blotting
A technique to identify RNA molecules by hybridization that is analogous to Southern blotting (see Southern blotting).

Nuclease
Any enzyme that can cleave the phosphodiester bonds of nucleic acid backbones.

Nucleoside
A five-carbon sugar covalently attached to a nitrogen base.

Nucleotide
A nucleic acid unit composed of a five carbon sugar joined to a phosphate group and a nitrogen base.

Nutrigenomics
The study of the interaction between diet, genes and environment and how they affect human health.