Question

Study the diagram given below and answer the questions that follows:

(a) Identify the structure shown in the above figure.
(b) Identify the labels P and Q.
(c) Write the nature of histone proteins.
(d) Distinguish between Euchromatin and Heterochromatin.

Hint:

Nucleosomes help compact DNA and regulate gene expression. Euchromatin is loosely packed and active, whereas heterochromatin is tightly packed and inactive.

Answer 1

Step 1 (a): The structure shown in the figure is a **nucleosome**, the fundamental unit of chromatin packaging in eukaryotes. 

Step 2 (b): 
Label P – DNA strand 
Label Q – Histone core (octamer of histone proteins) 

Step 3 (c): Histone proteins are **basic** in nature due to the abundance of positively charged amino acids (like lysine and arginine) which bind to the negatively charged DNA. 

Step 4 (d):

Property	Euchromatin	Heterochromatin
Staining and Packing	Lightly stained, loosely packed DNA	Densely stained, tightly packed DNA
Transcription Activity	Transcriptionally active	Transcriptionally inactive
Amount during Interphase	Found in greater amount during interphase	Found in lesser amount during interphase