Glossary Plant Breeding

Germinal Mutations. Mutations occurring in the cells that are destined to develop into
gametes.
Germplasm Theory (Weismann 1834-1914). An accepted theory of evolution that
disproved pangenesis theory of inheritance. The theory states that multicellular
organisms give rise to two types of tissues: somatoplasm and germplasm. Only
germplasm enters into reproductive processes and continuity of germplasm between
all descendant generations account for the many observed similarities that are
inherited. Somatoplasm, on the other hand, consists of tissues that are essential for the
functioning of the organisms but that lack the property of entering into sexual
reproduction.
Gene Interaction. Modification of gene action by a non-allelic gene(s). it may be the
collaboration of several different genes in the production of one phenotypic character
(or related group of characters).
Gene Map. A linear designation of mutant sites within a gene, based on the various
frequencies of interallelic (intragenic) recombination.
Gene Mutation. A point mutation that results from changes within the structure of a
gene.
Gene Pair. The two copies of a particular gene present in a diploid cell (one in each
chromosome set).
Gene Pool. The sum total of genes that occur in the reproductive gametes of a population.
It can be considered as a gametic pool from which samples are drawn at random to
form the zygotes of the next generation.
Gene Rearrangement. The process of programmed changes in the DNA structure of the
somatic cells, leading to changes in gene number or in the structural and functional
properties of the rearranged gene.
Gene Replacement. The insertion of a genetically engineered transgene in place of a
resident gene that is often achieved by a double crossover.
Gene Tagging. Mapping of genes of economic importance close to known markers. Thus
a (molecular) marker very closely linked to a gene of interest can act as a tag. This tag
(molecular marker) can be used for indirect selection of the target gene in the
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