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Some of the important functions of Nucleus are as follows:
J. Hammerling in 1934 demonstrated that the nucleus controls the functions of the cells and ultimately the characters of the individuals by conducting experiments on Acetabularia, a unicellular marine alga.
Acetabularia has a stem between 3 and 5 cm long and a cap 1 cm in diameter. The nucleus is located in the basal or rhizoid end of the cell.
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In Acetabularia, nucleus can be removed simply by cutting off the rhizoid.
The resulting enucleated cells are active in photosynthesis and can survive for many weeks.
Image Courtesy : upload.wikimedia.org/37/Wilson1900Fig2.jpg
Each Acetabularia species has a particular cap morphology. If a nucleus from A. crenulata is implanted into an enucleated A. mediterranea from which the cap has also been removed, the resulting cell will eventually develop a cap of the A. crenulata type. If two nucleate cells of different species are grafted together, a hybrid having a cap of intermediate morphology is formed. This result clearly demonstrates that the shape of the cap is determined by the nucleus.
Although dependent on the nucleus, cytoplasm has some degree of functional autonomy. The information required to form the cap passes to the cytoplasm before cap formation, where it can be stored in an inactive form. A. crenulata does not form a cap in the darkness, it only form an elongated stem. If such a stem is enucleated and then exposed to light, a cap will develop.
Therefore, cap formation triggered by light is not dependent on new nuclear activity, and all the necessary information is present in the cytoplasm but is not converted to the final active form until a light stimulus is present. This cap formation can be prevented by inhibitors of protein synthesis.
The information for cap production is very stable. Enucleated stalks maintained in the dark for weeks are still able to produce a cap upon illumination. This experimental result is probably due to the presence of stable mRNA molecules stored in the cytoplasm.
