Notes on DNA, RNA and Chromosomes

DNA, RNA and Chromosomes, Notes for RRB NTPC, RRC and SSC exams

DNA, RNA and Chromosomes, Notes for RRB NTPC, RRC and SSC exams
Biology is the the most important subject in the recent RRB, SSC or any other exams. The trand of question from science continuesly rising.To avail the opertunity we provide this article on DNA, RNA and Chromosomes that will surly help you in the exam.
To better understand this article you should read my article on Cell : The Unit of Life

DNA (Deoxyribonucleic Acid)

  • DNA is a molecule that carries genetic instruction for growth, devlopment, etc. of an organism.
  • It is a polynucleotide, composed of monomer units called nucleotides. This nucleotides are made up of one of four nitrogenous, Adenine (A), Guanine (G), Cytosine (C) and Thymine (T).

RNA (Ribonucleic Acid)

  • It is made up of a long chain of nucleotides essential in coding, decoding and regulation of genes.
  • It contains uracil as a nitrogenous base instead of thymine.
  • RNA is of three types : mRNA (Messanger RNA), tRNA (Transfer RNA) and rRNA(ribosomal RNA).


DNA, RNA and Chromosomes, Notes for RRB NTPC, RRC and SSC exams
  • Chromosomes are the heighly condensed coiled Chromatin fibers.
  • It is discovered by Walther Flemming in 1882.
  • Double Helical structure of DNA discovered by Watson and Crick and awarded Nobel Prize in 1962.
  • Adenine pairs with Thymine with two H-Bonds.
  • Guanine pairs with Cytosine with three H-Bonds.


Genes are specified sequence of nucleotides on a chromosomes, that encode particular protein which express in the form of some particular feature of the body.

Number of chromosomes found in Humans cells

Kind of cellChromosomes
In male
In female
1Body Cell46 (23 pairs) = 2n46 (23 pairs) = 2n
2Sex Cell23 = n23 = n

About Author

Photo of author
Hai, I am Avinash Prasad from Kolkata. I have7 years working experience in teaching field. cleared many Government Jobs exams - WBPTET, SBI Clerk, WBPSC Clerk, SSC CGL 2017, SSC CHSL, SSC MTS, Railway ALP & Technicians and RRB NTPC.

Leave a Comment