Chromosome Theory of Inheritance
The experiment of Theodore Boveri and other scientists are central to the development of chromosome theory of inheritance. It is necessary to understand these experiments and the line of reasoning of the scientists to fully appreciate how the chromosome theory of inheritance was developed.
Theodore Boveri’s Experiment
He performed his experiment using sea urchin eggs. Usually double fertilization does not occur in animals unlike in flowering plants where double fertilization animals, a membrane is formed covering the egg to prevent other sperms from entering the fertilized egg.
This is called monospermy. However, an egg may sometimes be fertilized by two sperms, this is called dispermy. With experiments on double fertilization of sea urchin eggs, Boveri contributed significantly to the development of Chromosome Theory of Inheritance.
He found eggs that had been fertilized by two spermatozoa. Since each sperm introduced a centrosome into the egg, and each centrosome divided in anticipation of the first cleavage division, the initial metaphases and anaphases were often characterized by a tetraster, which is a spindle with four poles.
Since the dividing nucleus was triploid, the distribution of the chromosomes to four poles in anaphase was irregular. Boveri isolated many of the first-division blastomeres from these dispermic eggs and demonstrated that most were abnormal in development, but that all were not alike in their abnormalities.
He concluded that abnormal development resulted from the irregular distribution of chromosomes brought on by the multipolar division. Each chromosome must consequently have possessed a certain individual quality that expressed itself in development.
Edmund Beecher Wilson’s Principle of Chromosome Theory of Inheritance
Four principles were laid down by Wilson as the foundation of the chromosome Theory of Inheritance:
The exact lengthwise division of the chromosomes at mitosis allows for the equal distribution of linearly arranged particles to the daughter cells.
The assumed material existence of the chromosomes in the nucleus between mitoses gives the genetic continuity necessary for the organs of heredity.
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The fact that the nucleus goes where things are happening shows its governing position in the work of the cell.
The quality of the chromosomes of the fusing germ cells corresponds to the equality of male and female in heredity.
These arguments had long been known but were still widely disputed or misunderstand at this time.
In summary, the major conclusion derived from chromosome theory of inheritance is that genes are arranged in a linear fashion on chromosomes.
Sutton and Boveri were credited with initiating the chromosome theory of inheritance, the idea that the genetic material in living organisms are contained in the chromosomes.
Work by others like Thomas H. Morgan, Alfred H. Sturtevant, calvin Bridges and other workers established beyond a reasonable doubt that Sutton’s and Boveri’s hypothesis was correct.
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