Looking for classes? Ksquare Career Institute, Bengaluru →
What are those structures that appear as 'beads-on-string' in the chromosomes when viewed under electron microscope?
A
Base pairs
B
Genes
C
Nucleotides
D
Nucleosomes
Detailed Solution
In eukaryotes the negatively charged DNA is wrapped around a positively charged histone octamer (two molecules each of H2A, H2B, H3 and H4) to form a nucleosome.
A typical nucleosome contains about 200 bp of DNA helix.
Nucleosomes are the repeating units of chromatin; under the electron microscope they are seen as 'beads-on-string'.
The beads are the nucleosomes and the string is the linker DNA joining them.
Base pairs, nucleotides and genes are far too small or are not discrete structures visible in this way.
Hence the structures are nucleosomes.
A typical nucleosome contains about 200 bp of DNA helix.
Nucleosomes are the repeating units of chromatin; under the electron microscope they are seen as 'beads-on-string'.
The beads are the nucleosomes and the string is the linker DNA joining them.
Base pairs, nucleotides and genes are far too small or are not discrete structures visible in this way.
Hence the structures are nucleosomes.