What is DNA? What is RNA? In this post, we are providing notes on DNA, RNA, Virus and Bacteria. These are important topics and questions from these topics are frequently asked in the government recruitment exams in India. One-liner type questions are asked from these topics and are beneficial for Railways and other competitive exams.
What is DNA - Deoxyribo Nucleic Acid (DNA) :

• DNA stands for Deoxyribonucleic Acid, it was discovered by Frederic Mischer.


• DNA is a double-stranded molecule made up of an elongated chain of sub-units called nucleotides.


• DNA is mainly found in the nucleus and in small amount it is also found in mitochondria an chloroplast.


• Chemically a nucleotide has three components.
(1) Nitrogenous base (2) Pentose Sugar (3) Phosphate group.

• Nitrogenous base is of two type i.e.Purine & Pyrimidines.


• Purines contain two nitrogen base i.e. Adenine and Guanine.


• Pyrimidine nitrogen bases are Thymine and Cytosine, thus there are four kinds of nucleotide present in DNA i.e. Adenine, Guanine, Thymine, Cytosine.

What is DNA - Structure of DNA :

• Watson and Crick give the structural model of DN


• DNA molecule is consists of two polynucleotide strand, forming a double helix structure.


• Each strand has a backbone of sugar and phosphate, nitrogen base is attached to the sugar.


• Two strands are joined together by hydrogen bonds between the bases.


• Adenine pairs with thymine whereas guanine pairs with cytosine.


• Adenine and thymine are complementary to each other and cytosine is complementary to guanine.

What is DNA - Functions of DNA:

• DNA is genetic material and contains genetic information in coded form.


• DNA has two main function replication and expression.

What is RNA - Ribonucleic Acid (RNA) :

• RNA stands for Ribonucleic acid.


• RNA is single-stranded nucleic acid made up of phosphate, a ribose sugar and nitrogen base uracil, adenine, guanine and cytosine.


• It is found in the nucleus as well as cytoplasm.


• Its main function is to synthesise the protein.

RNA is of three kinds.
1.Messenger RNA (mRNA): It brings the message from DNA found in the nucleus to cytoplasm in the coded form.
2.Ribosomal RNA (rRNA): Present in ribosome which is the site of protein synthesis.
3.Transfer RNA (t RNA): It is the carrier of amino acid and transfers it to the ribosome.
What is a Virus?:

• Virus was discovered by Russian Scientist Iavanosky during the test of Mosaic disease in Tobacco.


• Virus acts as a link between the living and non-living.


• Virus is dead but when it comes in contact with the living cell it gets activated.


• ‘The virus in which RNA is found as the genetic material is called Retrovirus.

Virus is of three types:
1. Plant Virus: RNA is present as its nucleic acid
2. Animal Cell: DNA and sometimes RNA is found in it.
3. Bacteriophage: They kill the bacteria e.g. T-2 phage.
What is a Bacteria?:

• Bacteria was discovered by Antony von Lecuwenhoek and its study is known as bacteriology.


• Bacteria is of different types on the basis of shape:

1. Bacillus: This is a rod like or cylindrical.
2. Round or Cocus: These are round and smallest bacteria.
3. Comma shape or vibrio
4. Spirillum: Spring or Screw shaped. Anabaena and Nostoc cyanobacteria xed the atmospheric nitrogen into the soil.