NEETZoologyMolecular Basis of Inheritance
A segment of eukaryotic DNA is 2000 base pairs long. If this entire segment is packaged into nucleosomes, what will be the number of nucleosomes formed and the total number of histone protein molecules (including H1 histones) associated with this segment?
Options
- A10 nucleosomes and 80 histone molecules
- B10 nucleosomes and 90 histone molecules
- C20 nucleosomes and 180 histone molecules
- D10 nucleosomes and 10 histone molecules
Correct answer
B. 10 nucleosomes and 90 histone molecules
Step-by-step solution
A typical nucleosome contains 200 base pairs (bp) of DNA helix. Number of nucleosomes = Total base pairs / Base pairs per nucleosome = 2000 / 200 = 10 nucleosomes. Each nucleosome consists of a histone octamer (8 histone molecules) and is associated with one H1 linker histone. Thus, the total number of histone molecules per nucleosome is 8 + 1 = 9. Total number of histone molecules = Number of nucleosomes Histones per nucleosome = 10 9 = 90 histone molecules. Therefore, 10 nucleosomes and 90 histone molecules will