Glossary Plant Breeding

evolutionary genetics into descent with modification; often referred to as the Modern
Evolutionary Synthesis.
Neolithic Age. Cultural period beginning ~12,000 years ago; appearance of technically
advanced stone tools.
Neurospora. A pink mould that is commonly found growing on old food.
Neutral Mutation. A mutation that has no effect on the biological fitness of its carriers.
It is also defined as a kind of mutation that has no phenotypic effect. It may be so
because the altered codon specifies functionally equivalent amino acid in the
polypeptide [e.g., AAA (lysine) to AGA (arginine); both are basic amino acids].
Neutral Polymorphism. A kind of polymorphism which is sustained owing to neutral
effects of alleles on survival and reproduction of genotypes.
NHI. Nitrogen Harvest Index. It refers to partitioning of nitrogen between grain and the
remaining plant-parts. In semi-dwarf wheat, the new varieties have a greatly improved
NHI.
Niche. A group of multidimensional environmental factors of an ecosystem to which a
population fits. According to Mayr (1963), it deals with the outward projection of
needs and the specific way of utilizing the environmental factors by the individuals of
the population.
Nicking. Nuclease action to sever the sugar-phosphate backbone in one DNA strand at
one specific site.
nif Genes. A cluster of genes orchestrated to produce the enzyme nitrogenase. More than
22 such genes are known. Out of these, only three (H, D, and K) are structural; some
are regulatory (A, L, etc.), and the rest may assist in making the expressed product
fully functional.
Nitrocellulose Filter. A type of filter used to hold DNA for hybridisation.
Nitrogen bases. Types of molecules that form important parts of nucleic acids. These are
composed of nitrogen containing ring structures. The two strands of a DNA double
are linked with each other through hydrogen bond established between
complementary bases.
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