Glossary Plant Breeding

Chimera. A plant (rarely an animal) composed of genetically distinct tissues owing to
mutation, somatic segregation or grafting. According to their structure, chimera may
be sectorial (different tissues growing side by side and occupying distinct sectors of
varying size), periclinal (one tissue placed centrally and the second grows around it as
the covering layer), and mericlinal (actually an interrupted periclinal chimera).
Chimeric Genes. Genes generated through rearrangement and shuffling of other genes
having their own coding and regulatory domains.
Chlorophyll. An asymmetrical molecule with porphyrin hydrophilic head composed of
four pyrrole rings forming a complex with an Mg atom. The molecule has also a long
hydrophobic phytol chain attached to one of the rings. There are several types of
chlorophyll (a, b, c, d, and e). Types a and b are found in chloroplasts of higher
plants.
Chloroplast. A chlorophyll-containing organelle (plastid) in plants, serving as the site of
photosynthesis. Besides chlorophyll, it also contains carotenoid pigments. It seems to
arise from pre-existing chloroplasts. It has its own DNA, and is considered semiautonomous.
Chondroid. A cell organelle in bacteria, which is functionally equivalent to the
mitochondrion of higher organisms.
Chromatid. One of two thread-like structures formed by the longitudinal division of a
chromosome during prophase, and known as daughter chromosome during anaphase.
Chromatid Conversion. A type of gene conversion that is inferred from the existence of
identical sister-spore pairs in a fungal octad that shows a non-Mendelian allele ratio.
Chromatid Interference. A situation wherein the occurrence of a crossover between any
two non-sister chromatids affects the probability of those chromatids being involved
in other crossovers in the same meiosis.
Chromatid Segregation. See double reduction.
Chromatophore. Any particle isolated from photosynthetic bacteria, which contains
photosynthetic pigments. Chromatophores are scattered throughout the cytoplasm of
such bacteria.
Chromogene. Any gene localised in chromosomes as opposed to cytogene.
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