Amino acid responsible for formation of histone- nucleic acid complex -

Ans. is 'd' i.e., Lysine Nucleosomeso Nucleosomes are primary structural units of chromatin. It consists of DNA bound to protein histones, i.e. core of protein histones wrapped with DNA.o Histones are basic proteins rich in lysine and argininine. These positively charged amino acids interact with negatively charged phosphate group of DNA.o There are five types of histones HI, H2A, H2B, H3 and H4. Two molecules of each H2A, H2B, H3 and H4 associate one another to form histone octomer. Around histone octomer a segment of the DNA helix is wound nearly twice forming nucleosome core.o A nucleosome associated with histone H1 is called chromatosome.o A series of nucleosome ("beads on a string") form a polynucleosome or chromatin. The DNA connecting two nucleosomes is called linker (or spacer) DNA. To linker DNA, H1 histone is attached to stabilize the complex. Non-histone proteins are also attached to linker DNA. These repeating units of nucleosomes, connected with linker DNA, form chromatin fiber.A polynucleosome (chromatin)o This winding of DNA around histones produce net shortening of DNA so that it can be accommodated in the nucleus. Further shortening is brought about by further coiling of chromatin fiber to produce solenoid structure with six nucleosome per turn. The Solenoids are further folded and condensed to form chromosomes.