Question

The histones facilitate the coiling of DNA molecule to form

• A. Polynucleotide
• B. Chromatin fibre
• C. Polypeptide
• D. Polysachharide

Answer 1

The correct option is B Chromatin fibre

Histones are the special type of low molecular weight, positively charged proteins which are rich in basic amino acids like lysine and arginine. There are five types of histone proteins, HI, H2A, H2B, H3, and H4. Four of them (H2A, H2B, H3, and H4) occur in a pair to produce histone octamer called the core of nucleosome. The positively charged end of these histones proteins are towards outside, to attract and hold firmly the negatively charged strand of DNA. About 166 bp of DNA is wrapped over the nucleosome body.

The DNA connecting the two adjacent nucleosomes is called linker DNA. It bears H1 histone protein which connects one core particle with the other. This completes the structure a negatively charged DNA wrapped around the positively charged histone octamer called nucleosome. The nucleosome and linker DNA are together referred to as chromatosome. The nucleosomal organisation has approximately 10 nm thickness which gets condensed and coil to form a solenoid of 30 nm diameter. The coiling undergoes further coiling to produce a chromatin fibre of 30-80 nm, then a chromatid of 700 nm.

Hence the histones facilitate the coiling of DNA molecule to form Chromatin fibre. So, the correct answer is 'Chromatin'.