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- N
- (1) In DNA or RNA, an unknown nucleotide. (2) In proteins, asparagine.
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- natural selection (selection)
- Differential reproduction of different members of a species due to the variability in fitness among individuals or genotypes, leading to changes in allele frequencies over time.
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- NCBI
- National Center for Biotechnological Information.
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- negative selection (see purifying selection)
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- neighbor-joining
- An algorithm for constructing phylogenetic trees using distance data.
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- neutral theory (neutral-mutation theory or neutral-mutation hypothesis)
- The proposal that evolution at the molecular level is primarily determined by mutational input and random genetic drift, rather than by natural selection.
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- NNI
- Nearest Neighbor Interchange.
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- node
- The graphical representation in a phylogenetic tree of an extant or ancestral operational taxonomic unit.
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- nondegenerate site
- A nucleotide site in the coding region at which all substitutions are nonsynonymous.
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- nondisjunction
- The failure of homologous chromosomes to separate during meiosis.
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- nonfunctionalization (silencing)
- The turning of a functional gene into a pseudogene following the occurrence of an incapacitating mutation.
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- nongenic DNA
- The portion of the genome that does not contain genes.
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- nonsense codon (see termination codon)
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- nonsense strand
- The transcribed strand of a gene, the sequence of which is complementary to the RNA transcript.
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- nonsynonymous substitution (missense substitution)
- A substitution that alters a codon to that for another amino acid.
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- N-terminal (see amino terminal)
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- nucleotide (base)
- A molecule composed of a nitrogen base, a sugar, and a phosphate group. Any of the basic building blocks of nucleic acids.
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- nucleotide diversity
- A measure of polymorphism applied to nucleic acid sequences. The mean number of nucleotide differences per site between any two randomly chosen sequences from a population.
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- nucleotide substitution
- A mutation in which one nucleotide is substituted for another. In evolution, the substitution of a nucleotide by another nucleotide that becomes fixed in a population.
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- nucleotypic
- Referring to a function of a DNA sequence other than as a carrier of genetic information (e.g., serving as a skeleton for the nucleus).
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- nucleus (plural, nuclei)
- A membrane-enclosed organelle containing the chromosomes in eukaryotes.
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