structure. Vacuoles organises itself into a storage/ sequestration compartment. Example: Vacuoles store, most of the sucrose of the cell. i.
Sugar in Sugar beet and Sugar cane. ii. Malic acid in Apple. iii.
Acids in Citrus fruits. iv. Flavonoid pigment cyanidin rutinoside in the petals of Antirrhinum . .
. Nucleus Nucleus is an important unit of cell which controls all activities of the cell. Nucleus holds the hereditary information. It is the largest among all cell organelles.
It may be spherical, cuboidal, ellipsoidal or discoidal. It is surrounded by a double membrane structure called nuclear envelope , which has and kinetochore. Both the chromatids are united at centromere, whose number varies. The monocentric chromosome has one centromere and the polycentric chromosome has many centromeres.
Centromere contains a complex system of protein fibres called kinetochore . Kinetochore is the region of chromosome which is attached to the spindle fibre during mitosis. Besides primary there are few secondary constrictions, are present. Nucleoli develop from these secondary constrictions are called nucleolar organizers .
Secondary constrictions contain the genes for ribosomal RNA which induce the formation of nucleoli and are called nucleolar organizer regions (Figure . ). A satellite or SAT Chromosome is a short chromosomal segment or rounded body separated from main chromosome by a relatively elongated secondary constriction. It is a morphological entity in certain chromosomes.
Telomere is the terminal part of chromosome. It offers stability to the chromosome. DNA of the telomere has specific sequence of nucleotides. Telomere in all eukaryotes are composed of many repeats of short DNA sequences ( ’TTAGGG3’ sequence in Neurospora crassa and human beings).
Maintenance of telomeres appears to be an important factor in determining the life span and reproductive capacity of During cell division chromatin is condensed into an organized form called chromosome . The portion an eukaryotic chromosome which is transcribed into mRNA contains active genes that are nottightly condensed during interphase is called Euchromatin . The portion of an eukaryotic chromosome that is not transcribed into mRNA which remains condensed during interphase and stains intensely is called