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2. Nucleoplasm. semifluid, granular ground substance, known as nuclear sap or nucleoplasm. It is mai a, Teac oar ae RNA), proteins, enzymes, and minerals ay, , Nate clic seas first described by Fontana (1781) and the term nucleolus, was coined by Bowman (1840), , spherical structure, not enclosed by a membrane, {, # ean around the nucleolar organizer region or secondary constriction of the chromosomes,, A cell may have one or more nucleoli but its number remams constant for a particular species, For example, i human {, cells,there are five pairs of (13, 14, 15 and 21, 22 pairs of chromosomes) or nucleolar organizer., + The nucleolus is the site for mbosomal RNA (rRNA) synthesis, , 4. Chromatin network., , * Within the nucleoplasm, a network of twisted thread like structure called chromatin network is present., , + ttwas named by W. Flemming (1879) 4, * These thread like structure later termed as chromosomes by Waldeye (1888), , * Chromatin is a complex of DNA and Histones, , * When the chromosomes are stained at prophase two regions become distinct., , () Heterochromatin. It is that regions of chromosome that remain condensed and show positive dark staining., They are genetically inert and late replicating, , (ii) Eurchromatin. It is a lightly stained or non-condensed region, rich in DNA and is genetically active., , , , , , , , , , | No | Euchromatin 5 | Heterochromatin, , ji it ts an uncoiled genetic material during interphase. ‘tis a coiled or dense genetic material during interphase., 2 | Itis stained less with Feulgan stain. It is a stained darker with Feulgan stain,, , 3 _| It has less amount of DNA. Ithas more amount of DNA. |, 4 | His early replicating in the cell cycle. It is late replicating in the cell cycle. |, , , , , , Chromatin and Chromosome, + Chromatins are thread-like structures forming a network within the nucleus of the non-dividing cell. {, * During cell division it condenses into chromosomes, , TYPES OF CHROMOSOME, , Depending upon the position of centromere, the chromosomes may, be, , , , Metacentric. The centromere lies in the middle of the, , ae so that the two arms are almost coual, , ond ie t so that thes two arms become unequal,, 3 Acrocentric If the centromere is more near to one end than, the other. so that one arm is very‘long and the other one is, extremely small, it is called acrocentric chromosome, 4 Telocentric The centromere is terminal in position, so that, the chromosome has one arm only., , , , LONG al, TELOCENTRIC, , ACROCENTRIC, , SUB-METACENTRIC, , METACENTRIC, , Secondary Constriction, The non staining constriction found on few chromosomes at a constant location other than ceutromere (primary const, called as secondary constriction. The part of chromosome beyond the secondary constriction is called as Satellite, Striction) is, , ET mee | Mes ee ~) balowe Dey bea.