Question

Chromosome is made up of
(a) DNA +pectin
(b) RNA + amino acid
(c) DNA + histone
(d) Only histone

Answer 1

Hint: It is a thread-like structure which is located in the nucleus of eukaryotic cells. Chromosomes require basic protein for the packaging and formed chromatin fibers by condensation.

Complete answer:
A chromosome made up of DNA and histones. In humans, the length of the DNA of a diploid somatic cell is ${ 6.6\times 10 }^{ 9 }\quad bp\quad \times \quad { 0.34\times 10 }^{ -9 }m\quad =\quad 2.2\quad meters$. This length of DNA is much longer than the dimension of the nucleus which is nearly ${ 10 }^{ -6 }m$. Likewise, the dimension of the prokaryotic cell is 1µm but the length of prokaryotic DNA is approximately 1.36 mm that has to be placed inside the cell. With the help of packaging or compaction, this long sized DNA is accommodated in the smaller area through packaging or compaction. The packaging occurs by the folding and attachment of DNA with the histone proteins in eukaryotes and non-histone proteins in prokaryotes.

Additional Information:
1. Chromosomes may be simple or complex in structure in which a polynucleotide chain is held with some proteins.
2. DNA acts as genetic material in most of the organisms, while RNA mostly functions as a messenger, although it is the genetic material of few viruses.
3. In prokaryotes, the chromosome is a simpler structure, DNA not being scattered throughout the cell, although they do not have a well-defined nucleus.
4. In eukaryotes, the chromosome is complex, DNA being surrounded by a unit of eight positively charged basic protein molecules called histone octamers.
5. DNA takes one and 3/4th turn around a histone octamer, which contains 146 base pairs; remaining 1/4th DNA forms the connection between two histone complexes known as hanging DNA, which contains 54 base pairs.
6. This structure of negatively charged DNA surrounded by positively charged histone octamer is called a nucleosome, which is a threadlike, colored body seen in the nucleus.
7. Six histone complexes condense to form 1 ring of the solenoid.
8. Solenoid rings further constrict to form chromatin fibers.
9. The nucleosome is the basic unit of chromatin, which looks like a 'beads-on-string' structure under an Electron Microscope.
10. Nucleosomes in chromatin are packaged to form chromatin fibers that are further collected to form chromosomes during metaphase of cell division.

So, the correct answer is, “ DNA + histone.”

Note:
1. Histone protein mainly contains amino acids, lysine, and arginine.
2. There are five types of histone proteins -H1, H2A, H2B, H3, and H4.
3. Out of these except H1, all other forms the histone octamer while H1 works as an anchor and stabilizes the nucleosome.