Question

The association of histone ${ H }_{ 1 }$ with a nucleoside indicate
(a) The DNA double helix is exposed
(b) Transcription is occurring
(c) DNA replication is occurring
(d) The DNA is condensed into a chromatin fiber

Answer 1

Hint: The association of histone ${ H }_{ 1 }$ indicates the complete formation of nucleosomes. Histone bears a positive moiety which binds the negatively charged DNA.

Complete answer:
In the eukaryotic chromosome, a single DNA molecule of enormous length is present. The DNA is associated with a large range of protein molecules referred to as chromatin. The association of histone ${ H }_{ 1 }$ with a nucleoside indicates that the DNA is condensed into a chromatin fiber.
Histones, a basic protein interact with negatively charged DNA, as a result, the DNA winds around the histone core (consists of four different histones).
The core particles that are linked by DNA are associated with only one type of histone ${ H }_{ 1 }$. As a result, the chromatin looks like a bead in a string and these beads are nucleosomes. Here a large strand of DNA is converted into a beaded flexible fiber.
Further compaction occurs and finally, the condensation of these fibers into metaphase chromosomes occurs where DNA looks like a loop.
So, the correct answer is, “the DNA is condensed into a chromatin fiber.”

Note: -Histones were discovered in 1884 by Albrecht Kossel.
-“histone” is taken from the German word “Histon”
-${ H }_{ 3 }$ and ${ H }_{ 4 }$ histones have long tails produced from the nucleosome. At several places, they can be modified covalently.