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Q.
In eukaryotes basic structural unit made of histone and DNA:
Delhi UMET/DPMTDelhi UMET/DPMT 2006
Solution:
In eukaryotes DNA is tightly bound to histones which form a DNA protein particles called nucleosome. Each nucleosome contains $2$ copies of each $ H_{2}A,\,\,H_{2}B,\,\,H_{3} $ and $ H_{4} $ histone protein bounded on $146 \,BP$ of DNA. Each nucleosome bead is linked to next nucleosome bead by linker DNA. The chromosomes are the nuclear components of special organization, individuality and function. They are capable of self reproduction and play a vital role in heredity, mutation, variation and evolutionary development of species. Nudeolus was originally discovered by Fontana $(1781)$ and the present name is given by Bowman $(1840)$. It is naked, roughly rounded structure attached to chromatin at nucleolar organizer region. Lysosomes are small vesicles containing hydrolytic enzymes. They contain about $40$ acid hydrolases for digestion of various materials.