What are those structures that appear as 'beads-on-string' in the chromosomes when viewed under electron microscope?
Nucleotides
Nucleosomes
Base pairs
Base pairs
B.
Nucleosomes
Nucleosome is sub-microscopic sub-unit of chromatin which is formed by wrapping of DNA over a core of histone proteins. The term was coined by Oudet et. al, (1975). It is oblate structure with a length of 10 nm and a thickness of 5-5.7 nm. Its core is called nu-body. The latter is formed of four pairs of histone molecules - H2A, H2B, H3 and H4. DNA makes 1.75 turns over the octamer to form a nucleosome. Two adjacent nucleosomes are connected by a short segment of unbound DNA called linker DNA. A fifth type of histone called H1 is attached over the linker DNA. Nucleosomes appear as 'beads-on-string' in the chromosomes under electron microscope.
Silencing of mRNA has been used in producing transgenic plants resistant to
bollworms
nematodes
White rusts
White rusts
The process of RNA interference has been used in the development of plants resistant to
fungi
viruses
insects
insects
Which one of the following also acts as a catalyst in a bacterial cell?
sn RNA
hn RNA
23 S rRNA
23 S rRNA
The unequivocal proof of DNA as the genetic material came from the studies on a
bacterium
fungus
viroid
viroid
