Q1 of 33 Page 10

What are nucleosomes?

Nucleosome is the repeating subunits of the chromatin fibre. Each nucleosome is a ball-shaped structure which consists of a core particle of histone proteins wrapped by DNA strand. The core particle is composed of two molecules each of four different histones. A molecule of the fifth histone, called H1, attaches to the DNA near the bead.

A Nucleosome is 10 nm in diameter. A single human chromosome may have about a million nucleosomes.



More from this chapter

All 33 →
2

What are the rungs of the “DNA ladder” made of?

 3

Correct the following statements if there is any mistake.

(a) The four nitrogenous bases in the DNA are Guanine, Thiamine, Adrenaline, and Cytosine.


(b) Genes are specific sequences of bases on a chromosome.


(c) A nucleotide is composed of a sulphate, a sugar (pentose) and a nitrogenous base.


(d) Nucleosome is group of cysteine molecules surrounded by DNA strands.


(e) If there are 46 chromosomes in a cell, there will be 23 chromatin fibers inside the nucleus during interphase.

 2

What are genes?

 1

Given below is a schematic diagram of a portion of DNA.


(a)How many strands are shown in the diagram?


(b) How many nucleotides have been shown in each strand?


(c) Name the parts numbered 1, 2, 3, 4 and 5 respectively.


(d) Name the DNA unit constituted by the parts 1, 2 and 3 collectively.