The Principle of Segregation
These results can be explained using the principle of segregation.
- The traits variation observed was controlled by genes. These genes somehow store information in the cells of living things to direct the expression of traits. Genes can be changed to alternative forms called alleles.
- Genes are found in pairs in somatic cells that make up the plant.
- The paired genes separate during gamete formation. One gene from each pair goes into a gamete.
- The gametes fuse at random during sexual reproduction, producing the next generation (seed in this case).
Segregation describes the behavior of something that Dr. Specht could not see as he observed plants in the field. He cannot prove this is happening with his experimental data but he can test the validity of the principle in explaining his results. That is what we will try to do.
Dr. Specht started with a true breeding line that was homozygous at all of its gene pairs. There was no genetic variation among progeny in this line. The mutagen created an alternative allele at a gene pair controlling leaf traits and an allele at a gene pair that controls the growth of the plant. Once a gene is altered and a new allele created, the new allele will be stable and pass on this altered information from cell to cell and parent to offspring.