Why in news? Nucleic acids are naturally occurring chemical compounds that serve as the primary information-carrying molecules in cells. They play an especially important role in directing protein synthesis. The two main classes of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
Increasing variants of the covid-19 virus and their consequences on humans.
What is DNA?
- Genetic carrier -Deoxyribonucleic acid (DNA) is the molecule that carries genetic information for the development and functioning of an organism.
- Two strands -DNA is made of two linked strands that wind around each other to resemble a twisted ladder a shape known as a double helix.
- Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups
- The two strands are connected by chemical bonds called bases.
- Four bases -Adenine (A), cytosine (C), guanine (G) or thymine (T).
- Proofreading -The enzymes responsible for copying DNA, collectively known as DNA polymerases, possess error-correction property, known as ‘proofreading’.
What is RNA?
- Ribonucleic acid (RNA) is a nucleic acid present in all living cells that has structural similarities to DNA
- RNA is most often single-stranded
- An RNA molecule has a backbone made of alternating phosphate groups and the sugar ribose
- Attached to each sugar is one of four bases: adenine (A), uracil (U), cytosine (C) or guanine (G)
- Different types of RNA in cells are messenger RNA (mRNA), ribosomal RNA (rRNA) and transfer RNA (tRNA).
- Some RNAs are involved in regulating gene expression.
- RNA polymerases do not possess the ability to proofread
What is the difference between DNA and RNA viruses?
| DNA Virus | RNA Virus |
| The DNA virus include the members of the pox family (smallpox and chickenpox) and Hepatitis B. | The RNA virus include COVID-19, AIDS, polio, influenza, dengue, chikungunya, Ebola, Zika. |
| DNA viruses contain DNA as their genetic material | RNA viruses contain RNA as their genetic material |
| Double-stranded DNA viruses are more common than single-stranded DNA viruses | Single-stranded RNA viruses are more common than double-stranded RNA viruses. |
| Viral DNA is replicated inside the nucleus of the host cell | Viral RNA is first transcribed and then is replicated in the cytoplasm |
| DNA viruses are stable due to the lower mutation rate. | RNA viruses are unstable due to the higher mutation rate |
| DNA viruses shows an accurate replication. | RNA viruses shows an error-prone replication |
Why most viruses are RNA based?
- Most viruses are RNA based because
- They can encode their replication machinery
- High mutation rates
- Error-prone nature of their polymerases
- Acquire multiple adaptations
- Can exist in multiple variant forms simultaneously in each host
What are the consequences of RNA viruses?
- Survival advantage -Few odd variants possesses a survival advantage against a vaccine or a drug.
- Such variants will undergo further natural selection and the virus will continue to proliferate.
- Short generation time – In a very short period after infection the host’s virus population becomes enormous.
- Affects immune system -High viral output together with the diversity overwhelms the immune system.
- Zoonosis –The viruses can jump across species resulting in zoonosis.
- Spread easily among newer hosts -Because the high error rate and the short generation time enable the virus to adapt to newer conditions much faster.
A zoonosis (zoonotic disease) is an infectious disease that is transmitted between species from animals to humans (or from humans to animals).
