NEETZoologyMolecular Basis of Inheritance
In a hypothetical eukaryotic cell, a mutation causes all the lysine and arginine residues in histones to be replaced by glutamic acid and aspartic acid. What will be the immediate functional consequence of this mutation on chromatin packaging?
Options
- AThe histones will bind DNA even more tightly due to increased hydrogen bonding.
- BThe histone octamer will acquire a net positive charge and condense DNA irreversibly.
- CThe packaging will remain unaffected as the octamer structure is maintained.
- DThe histones will repel the negatively charged DNA, preventing the formation of nucleosomes.
Correct answer
D. The histones will repel the negatively charged DNA, preventing the formation of nucleosomes.
Step-by-step solution
In a normal eukaryotic cell, histones are rich in the basic amino acids lysine and arginine. These amino acids carry positively charged side chains, which are essential for binding the negatively charged DNA molecule to form nucleosomes. Glutamic acid and aspartic acid are acidic amino acids that carry negatively charged side chains at physiological pH. If lysine and arginine are replaced by glutamic acid and aspartic acid, the histone octamer will acquire a net negative charge. Since the DNA backbone is also negat