In the work of plant’s genetics and
breeding, genetic marker is an important tool. The main way to understand the
genes of these markers and their close linkage control characters of genes is
to analyze the separate types of genetic marker in the hybridize generations.
The ideal genetic marker mainly has four characters: 1. better polymorphism. 2. It shows comdominace, and distinguishes
homozygous genes or heterozygous genes.3. It has no effect to the main
agronomic character. 4. It has a few costs and very convenient to observe and
record. The current genetic markers have mainly four types, morphological
markers, cytology markers,
biochemistry markers and element markers. Morphological markers are the
outside characters of the plants, such as stem height, shape of plant ears,
grain color. It is simple and directly seeing, but it lacks in quantity and polymorphism, and can be easily affected by
the environment. What’s more, many morphological markers have bad
effects on important agronomic characters. Cytology markers are mainly chromosomal karyotype(satellite, centromere and so on) and
banding(C,N,G); Biochemistry markers mainly concludes isozyme and seed
starage protein, and it is economic and convenient. But they two have so
limited quantities that cannot meet the needs of genetic and breeding.Element markers are
based on the DNA level, and it has 3 different characters as follows: 1. It
shows with the form of DNA and not affected by the environment. It can be
examined in different periods of the plant’s growth and different
organizations. 2. It has a big quantity and scatter over the whole genome. 3.
It has a high level of polymorphism. 4. It has no
effect on the expression of goal characters and has no inevitable link to the
bad characters. 5. Many element markers shows dominance and comdominace in inheredity, with which can distinguish
homozygous genes and heterozygous genes.
