Question

By which chromosomes are made of?
A. DNA and RNA
B. DNA and proteins
C. DNA only
D. Proteins only

Answer 1

Hint: A chromosome is a thread-like structure present in the nucleus. A human has 23 pairs of chromosomes. In an offspring, one set of the chromosome is maternal and another is paternal. It is made up of the genetic material along with histones.

Complete answer:
A chromosome consists of DNA and protein. Major proteins in chromatin are histone proteins. These are meant for the packaging of DNA into the compact small nucleus. Long DNA must fit into a small cell and a small nucleus of the cell hence, the packaging of DNA occurs. Histone provides structural support to chromosomes, long DNA wraps around the histone protein and forms the compact structure. Histones are positively charged proteins that strongly bind to the negatively charged DNA molecule. Nucleosomes are the structural unit of chromatin. A single nucleosome consists of a base pair of DNA sequences. Nucleosomes are arranged like beads on a string, they fold themselves again and again and form dense chromosomes. Two turns of DNA wrap around histone proteins from the nucleosome, this Octamer of histone includes H2A, H2B, H3, and variants of histones. Histone protein acts as a linker protein between two nucleosomes and it binds to linker DNA. RNA is Ribonucleic acid is essential for coding, expression and regulation of genes.

So, the correct answer is option B.

Note: A human cell has six feet long DNA packed into the nucleus with a diameter less than a human hair. By reducing the positive charge on a histone protein, binding with DNA is reduced and this is useful in the process of transcription. During the process of replication, histone dissociates and along with DNA these proteins also get replicated.