Glossary Plant Breeding

Unineme Theory. A theory that states that each chromatid represents a single linear
DNA molecule with its associated proteins.
Uniparental Inheritance. A kind of inheritance in which the transmission of certain
phenotypes occurs from one parental type to all the progeny. Such inheritance is
generally produced by organelle genes (mit-genes, plastomes).
Uniparental. Having only a single parent – parthenogenetic.
Unisexual. Of organisms having separate sexes (dioecious) and producing only one kind
of gametes. Such organisms are thus dimorphic.
Unit Character. A character difference which is transmitted as a unit in heredity; a
character difference controlled by one pair of alleles.
Unit Membrane (Robertson 1959). The basic unit of the membrane system of any cell.
The plasma membrane represents a single unit membrane. All other membranous
structures of the cell are also unit membrane.
Univalent. An unpaired chromosome in meiosis; also called an asynaptic chromosome.
Univalents either lack a homologue or result from asynapsis (due to asynaptic genes
or influence of environmental factors). Bivalents, trivalents, quadrivalents, etc. are
associations of 2, 3, 4, etc. homologous chromosomes held together by chiasmata.
Unpredictable Legume. A legume yield potential of which cannot be assessed visually
owing to underground formation of economic products. Peanut sometimes is called
unpredictable legume; however, there are other legumes also (yam bean, for example)
which form underground economic parts.
Unstable Mutation. A mutation having high frequency of reversion. Such mutation may
be caused by the insertion of a controlling element, whose subsequent exit produces a
reversion.
UPOV (1961). Union Pour La Protection Des Obtention Vegetables. It is an acronym
derived from the fresh translation of above words meaning “International Union for
the Protection of New Varieties of Plants”. The objective of the UPOV convention
(also called Paris convention, 1961) was to allow the breeder to acquire the sole right
to commercialise the newly developed variety and/or multiply and commercialise
under license. Many countries in the developed world have adhered to the UPOV
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