Fill in the blanks:

(i) Chromatin fibre is made up of DNA and ………………………….

(ii) The chromatids are attached to each other at ………………………….

(iii) DNA replicates in the ..………………………………... of the cell cycle.

(iv) Who first discovered the structure of DNA? ………………………….

(i) Histone

The chromatin material is comprised of DNA and histones. DNA comprising of 40% and a certain type of protein called histone, the rest 60%.

(ii) Centromere

Each chromosome consists of two chromatids which are attached to each other at some point called centromere. Chromosomes are attached to spindle fibres at the centromere.

(iii) S phase

S phase or synthesis phase is the second stage of cell cycle. In this phase DNA synthesis takes place.

(iv) James Watson and Francis Crick

The structure of DNA was first discovered by Watson and Crick in 1953. They were awarded Nobel prize for this in 1962.