RNA Virus Vs DNA Virus

In the previous post, we learned about the classification of viruses. In this, let us look into the differences between DNA and RNA viruses.

RNA Virus	DNA Virus
Genetic material - RNA	Genetic material - DNA
Most of them are single-stranded	Most of them are double-stranded
Unstable compared to DNA viruses, high mutation rate	Stable, less mutation rate
RNA replication - in the cytoplasm of host cell	DNA replication - in the nucleus of the host cell
In Baltimore classification, Class III, IV, V, and VI are RNA viruses	In Baltimore classification, Class I, II and VII are DNA viruses
E.g.: Coronavirus, Picornavirus, Reovirus	E.g.: Adenovirus, Herpesvirus, Poxvirus
Diseases caused by RNA viruses: HCV, Ebola, SARS, HIV	Diseases caused by DNA viruses: Smallpox, Herpes, Human Papillomavirus infection

References :

• F, I. (2018, November 7). DNA and RNA Viruses. Difference Between. http://www.differencebetween.net/science/health/difference-between-dna-and-rna-viruses/.
• Lakna, B. (2017, December 6). Difference Between DNA and RNA Viruses | Definition, Classes, Biosynthesis, Similarities. Pediaa.Com. https://pediaa.com/difference-between-dna-and-rna-viruses/.
• Shaffer, C., PhD. (2019a, February 26). The Baltimore Classification System. News-Medical.Net. https://www.news-medical.net/life-sciences/The-Baltimore-Classification-System.aspx

Classification of Viruses

    The XE variant of Covid-19 has started spreading among people and it is a highly transmissible virus!!! Yes guys, it is Covid-19 pandemic period. Let us see about more viruses. Keep reading and keep sharing!

    What comes to our thought  when we hear the word "virus"? Yes, of course it is Covid-19! Since we have been living in Covid-19 pandemic period, for most of us virus means Covid-19. But there are many other viruses too. Generally, they are known as submicroscopic organisms, means they are not visible through microscope. They are present everywhere, and they are very tiny organisms with DNA or RNA as genetic material enclosed by a protein coat called capsid. Some of them will have envelope which is derived from the host cell. They are generally considered as non-living organisms due to the fact that viruses need a host cell and its components for its replication. Let us have a look on the types of viruses.

Viruses can be classified based on their,

1. Morphology (Based on shape and size)
2. Chemical composition and mode of replication (Based on nucleic acid type)

Morphology based classification

1. Helical Viruses - Tobacco Mosaic Virus
2. Polyhedral Viruses - Adenovirus
3. Spherical Viruses - Coronavirus
4. Complex Viruses - Bacteriophage

Chemical composition and Mode of replication

1. RNA Viruses - Coronavirus, Retrovirus
2. DNA Viruses - Adenovirus, Herpesvirus

    Viruses that have RNA as genetic material is called RNA viruses. They have elevated mutation rate due to the error rate of enzymes involved in RNA replication. RNA virus genome may be of single stranded (ss) or double stranded (ds) RNA. In the case of ssRNA, the RNA can be either sense strand which can function as mRNA or an antisense strand which cannot function as mRNA.

    Viruses that have DNA as genetic material is called DNA viruses. The subtypes are linear dsDNA, circular dsDNA, linear ssDNA and circular ssDNA. The examples of DNA and RNA viruses are mentioned in the below table.

RNA Viruses
Type of Nucleic acid	Examples
ssRNA (sense strand)	Picornavirus, Coronavirus
ssRNA (antisense strand)	Arenavirus, Orthomyxovirus
dsRNA	Reovirus
DNA Viruses
Linear dsDNA	Adenovirus, Poxvirus
Circular dsDNA	Papovavirus
Linear ssDNA	Parvovirus
Circular ssDNA	Circovirus

What is Baltimore System of Classification?

    Viruses do not have complete system for protein production. They are dependent on host cell translational machinery for the protein synthesis. So, the Baltimore system classifies the viruses into 7 groups based on the replication method and type of genetic material present. About 30 years ago, this classification was devised by David Baltimore, a virologist. In this, he assigned the mRNA at the core and the pathways to mRNA from DNA or RNA denotes different classes of viruses. The 7 types of viruses are summarized in the below table.

Baltimore Classification of Viruses
Group	Type of viruses	Examples	mRNA synthesis
Group I	dsDNA viruses	Herpes virus, Adenovirus	mRNA transcription directly from DNA template
Group II	ssDNA viruses	Parvovirus, Circovirus	ssDNA is converted to dsDNA. Then, mRNA transcription
Group III	dsRNA viruses	Reovirus, Birnavirus	mRNA is transcribed from RNA genome
Group IV	ssRNA viruses (positive-sense RNA)	Coronavirus, Picornavirus	Genetic material function as mRNA
Group V	ssRNA viruses (negative-sense RNA)	Paramyxovirus, Orthomyxovirus	mRNA is transcribed from RNA genome
Group VI	Positive-sense ssRNA reverse transcriptase viruses	HIV, Metavirus	Reverse transcription of RNA to DNA, DNA is incorporated into host cell, then subsequent mRNA transcription
Group VII	dsDNA reverse transcriptase viruses	Hepatitis B virus	Viral DNA replication through RNA intermediate, this RNA may serve as template to produce mRNA or may serve as mRNA

References :

• Shaffer, C., PhD. (2019, February 26). The Baltimore Classification System. News-Medical.Net. https://www.news-medical.net/life-sciences/The-Baltimore-Classification-System.aspx.
• Lumen Learning. (n.d.). Virus Classification | Biology for Majors II. https://courses.lumenlearning.com/wm-biology2/chapter/virus-classification.
• Gelderblom HR. Structure and Classification of Viruses. In: Baron S, editor. Medical Microbiology. 4th edition. Galveston (TX): University of Texas Medical Branch at Galveston; 1996. Chapter 41. Available from: https://www.ncbi.nlm.nih.gov/books/NBK8174/.
• Virus. (n.d.). Genome.Gov. https://www.genome.gov/genetics-glossary/Virus.
• A World of Viruses. (n.d.). Harvard Museums of Science & Culture. https://hmsc.harvard.edu/world-viruses.

               

               Thank you!

t

Basic terms used in Genetics

1. Chromosome - These are the structures that hold genetic information. There may be single chromosome as in bacteria or multiple chromosomes as in eukaryotic organisms.
2. Gene - It is unit of information that encodes a genetic characteristic. And it is the fundamental unit of heredity.
3. Allele - Different forms of a gene that occurs at the same locus on homologous chromosomes.
4. Trait - Certain characteristic of an individual that is inherited.
5. Genotype - Genetic constitution of an individual.
6. Phenotype - The observed characteristics of an individual.
7. Genome - The entire genetic material of an organism.
8. Locus - Location of a specific gene or a DNA sequence on a chromosome.
9. Homologous chromosomes - Chromosomes that are identical to each other in morphology (shape and structure) and genetic constitution (same gene sequence, centromere location, loci and chromosome length). A pair of homologous chromosome consists of chromosome from father (paternal) and chromosome from mother (maternal).
10. Homozygous - Similar alleles of a gene is present in the specific locus of a pair homologous chromosomes.
11. Heterozygous - 2 different alleles of a gene are present in the specific locus of a pair of homologous chromosomes.

References:

• P.Arora, M. (2005). Genetic Engineering (1st ed.). Himalaya Publishing House.
• Glossary of Genomics Terms. (2013, April 10). Genetics and Genomics | JAMA | JAMA Network. https://jamanetwork.com/journals/jama/fullarticle/1677346.

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Top 5 breakthroughs within the Biotechnology Industry in 2021

        Biotechnology has become one of the fast-growing field these days with its new inventions that support the environment, agriculture, healthcare, pharma industries and the list goes on. Surprisingly, biotechnology achieved more attention during the Covid-19 pandemic period, as this could help in much faster Covid-19 testing, vaccine development and created many job opportunities too. All the companies around the world were pushed to develop new testing kits, vaccine, and repurposed drugs (Thanks goes to the advancing Biotechnology!). The importance of biotechnology is increasing in faster pace as it is becoming a vital part in everyone's life. This growth has resulted in many major inventions in this field. Some of them are listed in this article.

Let us have a glimpse! 

1. Tissue Engineering - 4D printing

        The exciting breakthrough in the tissue engineering field is the development of self- healing substances using 4D printing. A gelatin-like hydrogel they can alter their shape, are cell compatible and recyclable which was developed by the research team in University of Chicago led by Eben Alsberg. 4D materials can change their geometric shape over the time with respect to the certain stimuli. They can change the structures together with the neighboring tissues and actively interact with the surrounding developing or healing tissues. So, these shape shifting materials can be the biggest achievement in tissue healing. 

2. Gene Editing

        The process of changing an organism's DNA is known as gene editing or genome editing. This technique allows the removal, addition and alteration of genetic material at specific site. Some specific nucleases and CRISPER-cas9 are being used as the efficient gene editing tools. The CRISPER technology created success in treating wide range of genetic diseases including ocular diseases, cancer, blood and neuro regenerative diseases. Now, a research study led by Helmholtz Zentrum München has found when a specific human endogenous retrovirus (HERV), a part of human genome is activated, it weakens the brain function significantly. In their research, they used the CRISPR technology to activate a specific group of HERVs in human stem cells and generated neurons. The viral elements turned on the specific genes involved in brain development. Due to this, the nerve cells in the brain lost their functionality. 

        As a next step of research, this team will study about the HERV deactivation and treatment for neurodegenerative disease.

3. Development of Vaccines

        From the start of Covid-19, the scientists in the worldwide have been studying for the development of vaccines to subside the massive spread of this life-threatening virus. So, with the help of biotechnology many scientists were able to produce dependable vaccines. A recent breakthrough in the vaccine development is by Dr. Katalin Karikó who produced mRNA covid-19 vaccines and awarded "2022 Vilcek Prize of Excellence in Biotechnology". Her studies shown that, tweaking the nucleosides makes the mRNA safe for vaccination against infectious agents. Using these, mRNA vaccines were developed by Pfizer and Moderna. These vaccines worked with more than 94% efficacy by reducing the symptoms. Thanks to Dr. Katalin Karikó for her ever lifesaving contribution!

4. Personalized Medicine

        In earlier days of research, drugs and medicines were formulated based on "one-size-fits-all". Much research had been undergoing to find out suitable drugs for the wide range of population. But, in the modern genomics it is possible to customize medicines for everyone based on their genetic makeup. Personalized medicine can be used for the understanding of how the genetic makeup of an individual affect the growth and spread of cancer cells in the body. Another application is preventative medicine, in which individuals with specific genetic makeup are susceptible to disease or disease condition can be given pre-emptive treatment.

        Personalized medicine is one of the booming research fields and which can be answer for the treatment of many diseases! This will be a biggest trend in 2022 also!

5. Environmental DNA

        Invasive ant species are causing great damage widespread. So early detection is necessary for the proper pest control at the right time. Environmental DNA is the DNA shed by diverse organisms into the aquatic or terrestrial environments. This eDNA technique helped researchers to find out the invasive species "Argentine ant " from the soil of Kobe’s Port Island and Kyoto’s Fushimi district, and they caused huge destruction.

        This new method can be used to find out the hotspot of many invasive organisms which cause major harm such as fire ant, and effective pest control can be done to eradicate it.

Let us wait for more trends and innovations in 2022!

Thank you!!!

References:

• Corless, V. (2021, March 2). Shape-shifting 4D materials provide new opportunity for tissue engineering. Advanced Science News. https://www.advancedsciencenews.com/shape-shifting-4d-materials-provide-new-opportunity-for-tissue-engineering/.
• The viruses in our genes: When activated, they damage brain development. (2021). ScienceDaily. https://www.sciencedaily.com/releases/2021/05/210520133706.htm.
• Marr, B. (2021, December 10). The 5 Biggest Biotech Trends In 2022. Forbes. https://www.forbes.com/sites/bernardmarr/2021/12/08/the-5-biggest-biotech-trends-in-2022/?sh=1805ad16380f.
• McMillen, D. (2021, June 16). 10 Biotechnology Breakthroughs in 2021. Explore Biotech. https://explorebiotech.com/biotechnology-breakthroughs-2021/.
• Thesia, E. (2021, December 16). Top 7 trends and innovations within the Biotechnology Industry in 2021. Pivotal Scientific. https://pivotalscientific.com/scientific-library/top-7-trends-and-innovations-within-the-biotechnology-industry-in-2021/#tissue.
• O’Neill, M. (2021, May 28). Environmental DNA (eDNA) Analysis Could Contribute Towards More Effective Pest Control. SciTechDaily. https://scitechdaily.com/environmental-dna-edna-analysis-could-contribute-towards-more-effective-pest-control/?utm_source=TrendMD&utm_medium=cpc&utm_campaign=SciTechDaily_TrendMD_0