Question

Under an electron microscope, chromatin fibers appear like beads in a string. The beads are
A. Chromosomes
B. Nucleosomes
C. Solenoids
D. Chromonemas

Answer 1

Chromatin fibers are arranged in such a way that it forms a long DNA part of the molecule. They are packaged into thin and stringy fibers. They form a compact form which is heterochromatin or less compact form which is euchromatin.

Complete Answer:
- Chromatin fiber is found in the nucleus of the eukaryotic cells. It is made up of proteins and DNA. Through this combination, thread or string like structure chromosomes are formed. This Chromatin fibers helps in repair of the DNA, replication of DNA or cell division. It has beads like a structure called Nucleosomes. The nucleosome is the fundamental subunit of chromatin.
- We know that, Chromosomes is also the longest DNA molecule in an organism which is located inside the nucleus of animal and plant cells. The chromosomes are made up of protein and a single molecule of DNA. With the help of a light microscope, chromosomes can be easily seen. Under the electron microscope, it looks like a bead in string.
- From the above information, we can conclude that Nucleosomes which are the basic packing unit of DNA built from proteins around which DNA is coiled that appear in chromatin fibers like beads in string under an electron microscope.

Thus, the correct answer is option B.

Note: The main difference between chromatin and chromosome is that chromatin consists of the unravelled condensed structure of DNA for the purpose of packaging into the nucleus whereas chromosome consists of the highest condensed structure of the DNA double helix for the proper separation of the genetic material.