{"id":19672,"date":"2026-05-29T15:47:42","date_gmt":"2026-05-29T15:47:42","guid":{"rendered":"https:\/\/www.vedprep.com\/exams\/?p=19672"},"modified":"2026-05-29T15:47:42","modified_gmt":"2026-05-29T15:47:42","slug":"prions-and-viroids","status":"publish","type":"post","link":"https:\/\/www.vedprep.com\/exams\/cuet-pg\/prions-and-viroids\/","title":{"rendered":"Prions And Viroids For CUET PG 2027: Master Tips"},"content":{"rendered":"<h1>CUET PG: Structure, Replication, Diseases\u00a0 of Prions and Viroids<\/h1>\n<p>Prions and Viroids are important non-cellular infectious agents for CUET PG. They are frequently asked questions in life science entrance examinations. Prions and Viroids. Prions are infectious protein particles that cause neurodegenerative diseases in animals and humans, and viroids are small circular RNA molecules that infect plants. For conceptual and statement-based questions in CUET PG Biology, it is very important to know their structure, replication, pathogenicity and differences.<\/p>\n<h2>Why Prions and Viroids for CUET PG Are Crucial in Microbiology and Molecular Biology<\/h2>\n<p>Prions and viroids are two odd infectious agents that defy the usual understanding of life and infection. ( For CUET PG )<\/p>\n<p>Most infectious organisms have nucleic acids and cellular structures, but prions have no nucleic acids at all, and viroids have only naked RNA without a protein coat.<\/p>\n<p>These features of prions and viroids make them of great importance in molecular biology, genetics &amp; microbiology. <a href=\"https:\/\/exams.nta.nic.in\/cuet-pg\/\" rel=\"nofollow noopener\" target=\"_blank\">CUET PG exams<\/a> often have questions on the differences between viruses, viroids and prions.<\/p>\n<p>Students will be able to discuss the molecular structure, mode of transmission, host specificity and diseases caused by these agents. Many questions are also on the mechanisms of replication and the history of discovery.<\/p>\n<p>Prions are mostly associated with fatal neurodegenerative diseases in mammals, while viroids infect economically important crop plants. Prions and Viroids are perfect for conceptual MCQs and assertion-reasoning questions due to their strange biological behaviour.<\/p>\n<p><a href=\"https:\/\/www.vedprep.com\/exams\/cuet-pg\/\"><strong>VedPrep<\/strong><\/a> also provides regular preparation for Competitive exams like CUET PG, CSIR NET, IIT JAM, GATE &amp; assistant professor recruitment exams.<\/p>\n<p>A solid conceptual background in microbiology subjects, such as prions and viroid, prepares students to approach interdisciplinary biology questions confidently.<\/p>\n<h2>Prions and Viroids: Discovery and Historical Background<\/h2>\n<p>The discovery of prions and viroids changed the understanding of infectious agents, showing that infection can be caused by agents that lack conventional cellular structures. Each of these discoveries brought with it whole new biological concepts and major scientific recognition.<\/p>\n<p>Viroids were first described by Theodor Otto Diener in 1971 while investigating potato spindle tuber disease. Diener demonstrated that the infectious agent was much smaller than viruses and contained only single-stranded circular RNA.<\/p>\n<p>The discovery proved that viroids are the smallest known infectious agents. Prions were discovered by Stanley B. Prusiner in 1982.<\/p>\n<p>Prusiner hypothesised that certain infectious neurodegenerative diseases are caused by infectious proteinaceous particles devoid of nucleic acids. The term &#8220;prion&#8221; was coined from &#8220;proteinaceous infectious particle&#8221;. His work was sharply attacked for challenging the central role of nucleic acids in infectivity. Older textbooks often reduced prions to \u201cabnormal proteins.\u201d<\/p>\n<p>Recent work shows that prions can induce a conformational change in normal proteins. They thus can propagate disease in the absence of DNA or RNA. This idea is now central to protein misfolding research.<\/p>\n<h2>Prion Structural Organization<\/h2>\n<p>Prions are infectious proteins made up mainly of abnormal versions of a normal host protein called PrP. They do not have nucleic acids in their structure and are therefore fundamentally different from viruses, bacteria, fungi and protozoa.<\/p>\n<p>The normal cell protein is called PrP C, where the C stands for cell. It is a normal constituent of healthy nervous tissue.<\/p>\n<p>In prion disease, the normal protein is converted into an abnormally folded form. This abnormal form is called PrP Sc ( Scrapie ), after the sheep disease that is believed to be caused by prions. The abnormal PrP Sc has more beta sheets than alpha helices.<\/p>\n<p>This changed shape makes the protein resistant to enzymatic degradation and allows it to accumulate in neural tissues.<\/p>\n<p>Prions have no:<\/p>\n<ul>\n<li>deoxyribonucleic acid<\/li>\n<li>RNA<\/li>\n<li>Coat protein<\/li>\n<li>Cell membrane<\/li>\n<li>Metabolic machinery<\/li>\n<\/ul>\n<p>Prions do not have nucleic acids, so the ways we sterilize things by destroying DNA or RNA may not be enough to completely get rid of them. This property accounts for the presence of prions in contaminated surgical instruments and animal tissues.<\/p>\n<p>Many students wrongly assume that all infectious agents must have genetic material. Prions are a very important exception and, therefore, a high-yield topic in CUET PG examinations.<\/p>\n<h2>Structure and Molecular Organization of Viroids<\/h2>\n<p>Viroids are small, infectious RNA molecules that infect plants. They are composed only of circular single-stranded RNA. They lack protein coats and envelopes.<\/p>\n<p>The RNA molecule in viroids is usually 250-400 nucleotides long. Viroids can multiply and spread in susceptible plant hosts even without proteins. Their RNA shows extensive internal base pairing, leading to a rod-like secondary structure.<\/p>\n<p>The main structural features of viroids are:<\/p>\n<ul>\n<li>Circular ssRNA<\/li>\n<li>no capsid;<\/li>\n<li>No enveloppe<\/li>\n<li>Cannot code for protein<\/li>\n<li>High degree of internal complementary base pairing.<\/li>\n<\/ul>\n<p>Viroids are not translated into proteins like viruses. They require host cell enzymes for replication and movement.<\/p>\n<p>Most viroids infect higher plants and cause diseases that result in a loss of agricultural productivity. In CUET PG, questions are often asked comparing viroids with viruses.<\/p>\n<p>The main difference between viruses, prions and viroids is that viruses have nucleic acids enclosed in protein coats, while viroids have only naked RNA molecules.<\/p>\n<h2>Prion Replication Mechanism<\/h2>\n<p>Prions replicate by altering the conformation of proteins rather than by synthesizing nucleic acid. Among infectious agents, this mechanism is unique and is one of the most unusual biological processes known today.<\/p>\n<p>The abnormal PrP Sc protein binds to normal PrP C proteins and induces them to change to the same abnormal structure. These newly converted proteins continue to convert other normal proteins. This causes a cascade of protein misfolding.<\/p>\n<p>This leads to the accumulation of insoluble protein aggregates in nervous tissue. These aggregates are neurotoxic and produce the characteristic spongy holes in the brain tissue known as spongiform degeneration.<\/p>\n<p>Prion replication differs fundamentally from viral replication in the following ways:<\/p>\n<ul>\n<li>No DNA copies<\/li>\n<li>RNA cannot be transcribed-<\/li>\n<li>No ribosomal protein synthesis involved<\/li>\n<li>Changes in protein folding underlie replication<\/li>\n<\/ul>\n<p>It\u2019s a common misconception that prions \u201creproduce\u201d like living cells. Prions do not reproduce. They propagate by structural conversion of existing proteins.<\/p>\n<p>Students understand this distinction to correctly answer conceptual questions on examinations. Replication of Viroids in Plant Cells. Viroids replicate by a rolling circle mechanism with host RNA polymerases.<\/p>\n<p>Viroids don\u2019t have any protein-coding genes, but their RNA molecules know how to hijack plant cell machinery to reproduce.<\/p>\n<p>Replication generally takes place in the nucleus or the chloroplast, depending on the viroid group. The viroid RNA is the template for the host RNA polymerase to synthesize complementary RNA strands.<\/p>\n<p>The rolling-circle mechanism comprises several stages:<\/p>\n<ul>\n<li>Synthesis of long complementary strands of RNA<\/li>\n<li>Cleavage into molecules of unit length<\/li>\n<li>RNA fragment circularization<\/li>\n<li>Production of mature infectious viroids<\/li>\n<\/ul>\n<p>Some viroids possess ribozyme activity, which allows the self-cleavage of RNA intermediates during replication. This catalytic property is thought to be important in molecular evolution studies.<\/p>\n<p>Students often mix up viroid replication and viral replication. Viroids have no messenger RNA coding regions, so they do not produce proteins. They are copied using only the host enzymes already present in the plant cell.<\/p>\n<h2>Prion Disease<\/h2>\n<p>Prion diseases are fatal neurodegenerative diseases of humans and animals. These diseases have a slow course but ultimately cause severe brain damage and death.<\/p>\n<p>The human prion diseases include:<\/p>\n<ul>\n<li>Creutzfeldt-Jakob disease (CJD)<\/li>\n<li>Variant Creutzfeldt-Jakob disease (vCJD)<\/li>\n<li>Kuru<\/li>\n<li>Familial fatal insomnia<\/li>\n<li>Gerstmann\u2013Str\u00e4ussler\u2013Scheinker syndrome<\/li>\n<\/ul>\n<p>Animal prion diseases are:<\/p>\n<ul>\n<li>Sheep scrapie<\/li>\n<li>Mad cow disease (bovine spongiform encephalopathy)<\/li>\n<li>\u00a0Chronic wasting disease of elk<\/li>\n<\/ul>\n<p>Symptoms include memory loss, lack of coordination, behavioral changes, tremors and progressive dementia.<\/p>\n<p>The diseases are always fatal and untreatable. The emergence of bovine spongiform encephalopathy underscored the importance of prion biology to food safety and public health.<\/p>\n<p>The disease spread through cattle populations via contaminated animal feed. Prion diseases have also provided insight into other protein misfolding disorders, such as Alzheimer\u2019s disease and Parkinson\u2019s disease, but these are not true prion diseases.<\/p>\n<h2>Viroid-Induced Diseases of Plants<\/h2>\n<p>Prions and Viroids cause several economically important plant diseases affecting crop yield and quality, and agricultural trade.<\/p>\n<p>Their small genome does not limit their pathogenic potential.<\/p>\n<p>Important diseases caused by viroids are<\/p>\n<ul>\n<li>Viroid of potato spindle tuber<\/li>\n<li>Disease of coconut cadang-cadang<\/li>\n<li>Citrus exocortis virus<\/li>\n<li>Chrysanthemum stunting disease<\/li>\n<li>Sunblotch of avocado<\/li>\n<\/ul>\n<p>Infected plants may show retarded growth, leaf distortion, decreased fruit quality, chlorosis and deformities. The severity of the disease depends on plant species, viroid strain and environmental conditions.<\/p>\n<p>The first viroid to be discovered was the potato spindle tuber viroid, and it is still a classic example in microbiology textbooks. It produces long and deformed potato tubers, which reduces market value.<\/p>\n<p>Modern agricultural systems find it hard to control the spread of viroid, as infected plants may be asymptomatic in the early stages.<\/p>\n<p>The international movement of plant materials can also be a means of transmission. Often, CUET PG asks students to match the diseases with the causative agents. Thus, memorising the major viroid diseases is important.<\/p>\n<h2>Prions and Viroids: Critical Concepts and Misconceptions For CUET PG<\/h2>\n<p>There are several misconceptions about prions and viroids often encountered in examination preparation. These conceptual errors, if corrected, will enhance analytical accuracy in solving CUET PG questions.<\/p>\n<p>One common misconception about prions and viroids is that prions are living organisms. Prions have no metabolism, no reproduction, no cellular organization.<\/p>\n<p>The infectivity is only a consequence of protein conformational changes. Another misconception is that viroids code for proteins. Viroids are RNA molecules but lack the open reading frames required for protein synthesis.<\/p>\n<p>Their pathogenicity depends on the disruption of host cell regulation. Some of the simplified teaching approaches present the prions as rare exceptions of limited biological relevance.<\/p>\n<p>The biology of prions and viroids is very interesting and very relevant to biomedical science. Many mechanisms related to protein misfolding may contribute to more general neurodegenerative processes.<\/p>\n<p>Students should also steer clear of memorising isolated facts without understanding mechanisms. CUET PG is now asking more application-based questions where conceptual clarity is more important than rote learning.<\/p>\n<p>Analytical preparation includes comparison of structure, replication, host specificity and disease pathology across infectious agents. This method of comparison is useful for remembering and exams.<\/p>\n<h2>Practical and Applied Significance of Research on Prions and Viroids<\/h2>\n<p>The study of prions and viroids is not just for exams, but has important applications in medicine, agriculture, molecular biology and biotechnology. Research on prions has contributed to a better understanding of neurodegenerative diseases and protein folding diseases.<\/p>\n<p>Scientists studying Alzheimer\u2019s disease, Huntington\u2019s disease and Parkinson\u2019s disease often study protein aggregation models inspired by prion biology.<\/p>\n<p>Viroid studies can be useful in plant pathology and crop protection programs. Early diagnosis methods help to reduce the losses in agriculture due to infected plant materials. Viroid detection relies heavily on molecular diagnostic methods such as RT-PCR.<\/p>\n<p>Prions and viroids can also affect sterilization practices in hospitals and research labs, since infectious proteins may not be removed by traditional disinfection methods. Instruments contaminated with prions need special decontamination procedures.<\/p>\n<p>From an evolutionary point of view, viroids are viewed as potential remnants of the primordial RNA world, owing to their simple RNA-centric organization and catalytic activities.<\/p>\n<p>VedPrep helps students connect examination concepts with real-life biology applications. This approach will improve conceptual understanding for CUET PG, CSIR NET, IIT JAM and other competitive examinations in life sciences.<\/p>\n<h2>Prions and Viroids: Important Exam Points for CUET PG<\/h2>\n<p>Prions and viroids are high-scoring topics for CUET PG, with students focusing on conceptual differences and recurring themes in the exams.<\/p>\n<p>Most questions concern structural features, replication mechanisms and disease associations.<\/p>\n<p>The important points to be revised are:<\/p>\n<ul>\n<li>Viroids are circular naked RNA molecules<\/li>\n<li>\u00a0Spongiform encephalopathies are caused by prions<\/li>\n<li>\u00a0Viroids mainly infect plants<\/li>\n<li>\u00a0Viroids replicate through rolling-circle replication<\/li>\n<li>\u00a0Prions spread by misfolding proteins<\/li>\n<li>\u00a0Prions were discovered by Stanley Prusine<\/li>\n<li>\u00a0Viroids discovered by Theodor Diener<\/li>\n<\/ul>\n<p>Statement-based questions often test students\u2019 ability to correctly identify viruses, viroids and prions. Comparative tables and conceptual revision are the best ways to master these questions. CUET PG Biology aspirants must blend the theoretical knowledge with repeated MCQ practice.<\/p>\n<p><a href=\"https:\/\/www.vedprep.com\/online-courses\/cuet-pg\"><strong>VedPrep<\/strong><\/a> offers focused coaching for topics like Microbiology, Molecular Biology, Genetics &amp; Biotechnology that are commonly asked in national-level entrance exams.<\/p>\n<h2>Frequently Asked Questions<\/h2>\n<style>#sp-ea-19713 .spcollapsing { height: 0; overflow: hidden; transition-property: height;transition-duration: 300ms;}#sp-ea-19713.sp-easy-accordion>.sp-ea-single {margin-bottom: 10px; border: 1px solid #e2e2e2; }#sp-ea-19713.sp-easy-accordion>.sp-ea-single>.ea-header a {color: #444;}#sp-ea-19713.sp-easy-accordion>.sp-ea-single>.sp-collapse>.ea-body {background: #fff; color: #444;}#sp-ea-19713.sp-easy-accordion>.sp-ea-single {background: #eee;}#sp-ea-19713.sp-easy-accordion>.sp-ea-single>.ea-header a .ea-expand-icon { float: left; color: #444;font-size: 16px;}<\/style><div id=\"sp_easy_accordion-1780069216\">\n<div id=\"sp-ea-19713\" class=\"sp-ea-one sp-easy-accordion\" data-ea-active=\"ea-click\" data-ea-mode=\"vertical\" data-preloader=\"\" data-scroll-active-item=\"\" data-offset-to-scroll=\"0\">\n\n<!-- Start accordion card div. -->\n<div class=\"ea-card ea-expand sp-ea-single\">\n\t<!-- Start accordion header. -->\n\t<h3 class=\"ea-header\">\n\t\t<!-- Add anchor tag for header. -->\n\t\t<a class=\"collapsed\" id=\"ea-header-197130\" role=\"button\" data-sptoggle=\"spcollapse\" data-sptarget=\"#collapse197130\" aria-controls=\"collapse197130\" href=\"#\"  aria-expanded=\"true\" tabindex=\"0\">\n\t\t<i aria-hidden=\"true\" role=\"presentation\" class=\"ea-expand-icon eap-icon-ea-expand-minus\"><\/i> 1. What are prions in biology?\t\t<\/a> <!-- Close anchor tag for header. -->\n\t<\/h3>\t<!-- Close header tag. -->\n\t<!-- Start collapsible content div. -->\n\t<div class=\"sp-collapse spcollapse collapsed show\" id=\"collapse197130\" data-parent=\"#sp-ea-19713\" role=\"region\" aria-labelledby=\"ea-header-197130\">  <!-- Content div. -->\n\t\t<div class=\"ea-body\">\n\t\t<p>Prions are infectious protein particles that lack nucleic acids such as DNA or RNA. They cause neurodegenerative diseases by converting normal proteins into abnormal, misfolded forms. Prions are highly resistant to heat, radiation, and enzymes, making them unique infectious agents important for CUET PG life science preparation.<\/p>\n\t\t<\/div> <!-- Close content div. -->\n\t<\/div> <!-- Close collapse div. -->\n<\/div> <!-- Close card div. -->\n<!-- Start accordion card div. -->\n<div class=\"ea-card  sp-ea-single\">\n\t<!-- Start accordion header. -->\n\t<h3 class=\"ea-header\">\n\t\t<!-- Add anchor tag for header. -->\n\t\t<a class=\"collapsed\" id=\"ea-header-197131\" role=\"button\" data-sptoggle=\"spcollapse\" data-sptarget=\"#collapse197131\" aria-controls=\"collapse197131\" href=\"#\"  aria-expanded=\"false\" tabindex=\"0\">\n\t\t<i aria-hidden=\"true\" role=\"presentation\" class=\"ea-expand-icon eap-icon-ea-expand-plus\"><\/i> 2. What are viroids?\t\t<\/a> <!-- Close anchor tag for header. -->\n\t<\/h3>\t<!-- Close header tag. -->\n\t<!-- Start collapsible content div. -->\n\t<div class=\"sp-collapse spcollapse \" id=\"collapse197131\" data-parent=\"#sp-ea-19713\" role=\"region\" aria-labelledby=\"ea-header-197131\">  <!-- Content div. -->\n\t\t<div class=\"ea-body\">\n\t\t<p>Viroids are small, circular, single-stranded RNA molecules that infect plants. They do not possess a protein coat and depend completely on the host plant machinery for replication. Viroids are considered the smallest known infectious agents and are commonly studied in plant pathology and molecular biology.<\/p>\n\t\t<\/div> <!-- Close content div. -->\n\t<\/div> <!-- Close collapse div. -->\n<\/div> <!-- Close card div. -->\n<!-- Start accordion card div. -->\n<div class=\"ea-card  sp-ea-single\">\n\t<!-- Start accordion header. -->\n\t<h3 class=\"ea-header\">\n\t\t<!-- Add anchor tag for header. -->\n\t\t<a class=\"collapsed\" id=\"ea-header-197132\" role=\"button\" data-sptoggle=\"spcollapse\" data-sptarget=\"#collapse197132\" aria-controls=\"collapse197132\" href=\"#\"  aria-expanded=\"false\" tabindex=\"0\">\n\t\t<i aria-hidden=\"true\" role=\"presentation\" class=\"ea-expand-icon eap-icon-ea-expand-plus\"><\/i> 3. What is the main difference between prions and viroids?\t\t<\/a> <!-- Close anchor tag for header. -->\n\t<\/h3>\t<!-- Close header tag. -->\n\t<!-- Start collapsible content div. -->\n\t<div class=\"sp-collapse spcollapse \" id=\"collapse197132\" data-parent=\"#sp-ea-19713\" role=\"region\" aria-labelledby=\"ea-header-197132\">  <!-- Content div. -->\n\t\t<div class=\"ea-body\">\n\t\t<p>The main difference is that prions are infectious proteins without nucleic acids, while viroids are infectious RNA molecules without a protein coat. Prions mainly infect animals and humans, whereas viroids infect plants. Their structure, replication mechanisms, and pathogenic effects are completely different.<\/p>\n\t\t<\/div> <!-- Close content div. -->\n\t<\/div> <!-- Close collapse div. -->\n<\/div> <!-- Close card div. -->\n<!-- Start accordion card div. -->\n<div class=\"ea-card  sp-ea-single\">\n\t<!-- Start accordion header. -->\n\t<h3 class=\"ea-header\">\n\t\t<!-- Add anchor tag for header. -->\n\t\t<a class=\"collapsed\" id=\"ea-header-197133\" role=\"button\" data-sptoggle=\"spcollapse\" data-sptarget=\"#collapse197133\" aria-controls=\"collapse197133\" href=\"#\"  aria-expanded=\"false\" tabindex=\"0\">\n\t\t<i aria-hidden=\"true\" role=\"presentation\" class=\"ea-expand-icon eap-icon-ea-expand-plus\"><\/i> 4. Why are prions called proteinaceous infectious particles?\t\t<\/a> <!-- Close anchor tag for header. -->\n\t<\/h3>\t<!-- Close header tag. -->\n\t<!-- Start collapsible content div. -->\n\t<div class=\"sp-collapse spcollapse \" id=\"collapse197133\" data-parent=\"#sp-ea-19713\" role=\"region\" aria-labelledby=\"ea-header-197133\">  <!-- Content div. -->\n\t\t<div class=\"ea-body\">\n\t\t<p>Prions are called proteinaceous infectious particles because they consist entirely of abnormal proteins capable of transmitting disease. Unlike viruses, they do not contain genetic material. Their infectious nature arises from their ability to induce structural changes in normal cellular proteins.<\/p>\n\t\t<\/div> <!-- Close content div. -->\n\t<\/div> <!-- Close collapse div. -->\n<\/div> <!-- Close card div. -->\n<!-- Start accordion card div. -->\n<div class=\"ea-card  sp-ea-single\">\n\t<!-- Start accordion header. -->\n\t<h3 class=\"ea-header\">\n\t\t<!-- Add anchor tag for header. -->\n\t\t<a class=\"collapsed\" id=\"ea-header-197134\" role=\"button\" data-sptoggle=\"spcollapse\" data-sptarget=\"#collapse197134\" aria-controls=\"collapse197134\" href=\"#\"  aria-expanded=\"false\" tabindex=\"0\">\n\t\t<i aria-hidden=\"true\" role=\"presentation\" class=\"ea-expand-icon eap-icon-ea-expand-plus\"><\/i> 5. Why are viroids considered subviral agents?\t\t<\/a> <!-- Close anchor tag for header. -->\n\t<\/h3>\t<!-- Close header tag. -->\n\t<!-- Start collapsible content div. -->\n\t<div class=\"sp-collapse spcollapse \" id=\"collapse197134\" data-parent=\"#sp-ea-19713\" role=\"region\" aria-labelledby=\"ea-header-197134\">  <!-- Content div. -->\n\t\t<div class=\"ea-body\">\n\t\t<p>Viroids are called subviral agents because they are simpler than viruses and lack a capsid or envelope. They consist only of naked RNA molecules and depend entirely on host enzymes for replication. Their minimal structure makes them distinct from conventional viruses.<\/p>\n\t\t<\/div> <!-- Close content div. -->\n\t<\/div> <!-- Close collapse div. -->\n<\/div> <!-- Close card div. -->\n<!-- Start accordion card div. -->\n<div class=\"ea-card  sp-ea-single\">\n\t<!-- Start accordion header. -->\n\t<h3 class=\"ea-header\">\n\t\t<!-- Add anchor tag for header. -->\n\t\t<a class=\"collapsed\" id=\"ea-header-197135\" role=\"button\" data-sptoggle=\"spcollapse\" data-sptarget=\"#collapse197135\" aria-controls=\"collapse197135\" href=\"#\"  aria-expanded=\"false\" tabindex=\"0\">\n\t\t<i aria-hidden=\"true\" role=\"presentation\" class=\"ea-expand-icon eap-icon-ea-expand-plus\"><\/i> 6. Which diseases are caused by prions?\t\t<\/a> <!-- Close anchor tag for header. -->\n\t<\/h3>\t<!-- Close header tag. -->\n\t<!-- Start collapsible content div. -->\n\t<div class=\"sp-collapse spcollapse \" id=\"collapse197135\" data-parent=\"#sp-ea-19713\" role=\"region\" aria-labelledby=\"ea-header-197135\">  <!-- Content div. -->\n\t\t<div class=\"ea-body\">\n\t\t<p>Prions cause neurodegenerative disorders such as Creutzfeldt\u2013Jakob disease, kuru, bovine spongiform encephalopathy, and scrapie. These diseases involve abnormal protein accumulation in nervous tissue, leading to brain damage, memory loss, and progressive neurological dysfunction.<\/p>\n\t\t<\/div> <!-- Close content div. -->\n\t<\/div> <!-- Close collapse div. -->\n<\/div> <!-- Close card div. -->\n<!-- Start accordion card div. -->\n<div class=\"ea-card  sp-ea-single\">\n\t<!-- Start accordion header. -->\n\t<h3 class=\"ea-header\">\n\t\t<!-- Add anchor tag for header. -->\n\t\t<a class=\"collapsed\" id=\"ea-header-197136\" role=\"button\" data-sptoggle=\"spcollapse\" data-sptarget=\"#collapse197136\" aria-controls=\"collapse197136\" href=\"#\"  aria-expanded=\"false\" tabindex=\"0\">\n\t\t<i aria-hidden=\"true\" role=\"presentation\" class=\"ea-expand-icon eap-icon-ea-expand-plus\"><\/i> 7. Which diseases are caused by viroids?\t\t<\/a> <!-- Close anchor tag for header. -->\n\t<\/h3>\t<!-- Close header tag. -->\n\t<!-- Start collapsible content div. -->\n\t<div class=\"sp-collapse spcollapse \" id=\"collapse197136\" data-parent=\"#sp-ea-19713\" role=\"region\" aria-labelledby=\"ea-header-197136\">  <!-- Content div. -->\n\t\t<div class=\"ea-body\">\n\t\t<p>Viroids cause plant diseases such as potato spindle tuber disease, citrus exocortis disease, and chrysanthemum stunt disease. These infections reduce crop productivity and affect plant growth by interfering with normal cellular metabolism and gene expression.<\/p>\n\t\t<\/div> <!-- Close content div. -->\n\t<\/div> <!-- Close collapse div. -->\n<\/div> <!-- Close card div. -->\n<!-- Start accordion card div. -->\n<div class=\"ea-card  sp-ea-single\">\n\t<!-- Start accordion header. -->\n\t<h3 class=\"ea-header\">\n\t\t<!-- Add anchor tag for header. -->\n\t\t<a class=\"collapsed\" id=\"ea-header-197137\" role=\"button\" data-sptoggle=\"spcollapse\" data-sptarget=\"#collapse197137\" aria-controls=\"collapse197137\" href=\"#\"  aria-expanded=\"false\" tabindex=\"0\">\n\t\t<i aria-hidden=\"true\" role=\"presentation\" class=\"ea-expand-icon eap-icon-ea-expand-plus\"><\/i> 8. Are prions living organisms?\t\t<\/a> <!-- Close anchor tag for header. -->\n\t<\/h3>\t<!-- Close header tag. -->\n\t<!-- Start collapsible content div. -->\n\t<div class=\"sp-collapse spcollapse \" id=\"collapse197137\" data-parent=\"#sp-ea-19713\" role=\"region\" aria-labelledby=\"ea-header-197137\">  <!-- Content div. -->\n\t\t<div class=\"ea-body\">\n\t\t<p>Prions are generally not considered living organisms because they lack cellular organization, metabolism, and genetic material. However, they are infectious and capable of self-propagation by inducing misfolding of normal proteins in host organisms.<\/p>\n\t\t<\/div> <!-- Close content div. -->\n\t<\/div> <!-- Close collapse div. -->\n<\/div> <!-- Close card div. -->\n<!-- Start accordion card div. -->\n<div class=\"ea-card  sp-ea-single\">\n\t<!-- Start accordion header. -->\n\t<h3 class=\"ea-header\">\n\t\t<!-- Add anchor tag for header. -->\n\t\t<a class=\"collapsed\" id=\"ea-header-197138\" role=\"button\" data-sptoggle=\"spcollapse\" data-sptarget=\"#collapse197138\" aria-controls=\"collapse197138\" href=\"#\"  aria-expanded=\"false\" tabindex=\"0\">\n\t\t<i aria-hidden=\"true\" role=\"presentation\" class=\"ea-expand-icon eap-icon-ea-expand-plus\"><\/i> 9. How do prions replicate inside the host?\t\t<\/a> <!-- Close anchor tag for header. -->\n\t<\/h3>\t<!-- Close header tag. -->\n\t<!-- Start collapsible content div. -->\n\t<div class=\"sp-collapse spcollapse \" id=\"collapse197138\" data-parent=\"#sp-ea-19713\" role=\"region\" aria-labelledby=\"ea-header-197138\">  <!-- Content div. -->\n\t\t<div class=\"ea-body\">\n\t\t<p>Prions replicate by converting normal proteins into abnormal prion forms through conformational changes. The abnormal protein acts as a template, causing healthy proteins to misfold. This chain reaction leads to accumulation of toxic protein aggregates in neural tissue.<\/p>\n\t\t<\/div> <!-- Close content div. -->\n\t<\/div> <!-- Close collapse div. -->\n<\/div> <!-- Close card div. -->\n<!-- Start accordion card div. -->\n<div class=\"ea-card  sp-ea-single\">\n\t<!-- Start accordion header. -->\n\t<h3 class=\"ea-header\">\n\t\t<!-- Add anchor tag for header. -->\n\t\t<a class=\"collapsed\" id=\"ea-header-197139\" role=\"button\" data-sptoggle=\"spcollapse\" data-sptarget=\"#collapse197139\" aria-controls=\"collapse197139\" href=\"#\"  aria-expanded=\"false\" tabindex=\"0\">\n\t\t<i aria-hidden=\"true\" role=\"presentation\" class=\"ea-expand-icon eap-icon-ea-expand-plus\"><\/i> 10. How do viroids replicate?\t\t<\/a> <!-- Close anchor tag for header. -->\n\t<\/h3>\t<!-- Close header tag. -->\n\t<!-- Start collapsible content div. -->\n\t<div class=\"sp-collapse spcollapse \" id=\"collapse197139\" data-parent=\"#sp-ea-19713\" role=\"region\" aria-labelledby=\"ea-header-197139\">  <!-- Content div. -->\n\t\t<div class=\"ea-body\">\n\t\t<p>Viroids replicate using host RNA polymerase enzymes through a rolling-circle mechanism. Since they lack protein-coding genes, they completely depend on host cellular machinery. Replication usually occurs inside the nucleus or chloroplasts of infected plant cells.<\/p>\n\t\t<\/div> <!-- Close content div. -->\n\t<\/div> <!-- Close collapse div. -->\n<\/div> <!-- Close card div. -->\n<!-- Start accordion card div. -->\n<div class=\"ea-card  sp-ea-single\">\n\t<!-- Start accordion header. -->\n\t<h3 class=\"ea-header\">\n\t\t<!-- Add anchor tag for header. -->\n\t\t<a class=\"collapsed\" id=\"ea-header-1971310\" role=\"button\" data-sptoggle=\"spcollapse\" data-sptarget=\"#collapse1971310\" aria-controls=\"collapse1971310\" href=\"#\"  aria-expanded=\"false\" tabindex=\"0\">\n\t\t<i aria-hidden=\"true\" role=\"presentation\" class=\"ea-expand-icon eap-icon-ea-expand-plus\"><\/i> 11. Why are prions resistant to sterilization?\t\t<\/a> <!-- Close anchor tag for header. -->\n\t<\/h3>\t<!-- Close header tag. -->\n\t<!-- Start collapsible content div. -->\n\t<div class=\"sp-collapse spcollapse \" id=\"collapse1971310\" data-parent=\"#sp-ea-19713\" role=\"region\" aria-labelledby=\"ea-header-1971310\">  <!-- Content div. -->\n\t\t<div class=\"ea-body\">\n\t\t<p>Prions are resistant to sterilization because their abnormal protein structure is highly stable and resistant to heat, ultraviolet radiation, and proteolytic enzymes. Conventional disinfection methods often fail to destroy them completely, making medical sterilization challenging.<\/p>\n\t\t<\/div> <!-- Close content div. -->\n\t<\/div> <!-- Close collapse div. -->\n<\/div> <!-- Close card div. -->\n<!-- Start accordion card div. -->\n<div class=\"ea-card  sp-ea-single\">\n\t<!-- Start accordion header. -->\n\t<h3 class=\"ea-header\">\n\t\t<!-- Add anchor tag for header. -->\n\t\t<a class=\"collapsed\" id=\"ea-header-1971311\" role=\"button\" data-sptoggle=\"spcollapse\" data-sptarget=\"#collapse1971311\" aria-controls=\"collapse1971311\" href=\"#\"  aria-expanded=\"false\" tabindex=\"0\">\n\t\t<i aria-hidden=\"true\" role=\"presentation\" class=\"ea-expand-icon eap-icon-ea-expand-plus\"><\/i> 12. What is the structure of a viroid?\t\t<\/a> <!-- Close anchor tag for header. -->\n\t<\/h3>\t<!-- Close header tag. -->\n\t<!-- Start collapsible content div. -->\n\t<div class=\"sp-collapse spcollapse \" id=\"collapse1971311\" data-parent=\"#sp-ea-19713\" role=\"region\" aria-labelledby=\"ea-header-1971311\">  <!-- Content div. -->\n\t\t<div class=\"ea-body\">\n\t\t<p>A viroid consists of a short circular single-stranded RNA molecule without any protein coat or envelope. The RNA forms extensive internal base pairing, giving it a rod-like secondary structure that contributes to stability inside host cells.<\/p>\n\t\t<\/div> <!-- Close content div. -->\n\t<\/div> <!-- Close collapse div. -->\n<\/div> <!-- Close card div. -->\n<\/div>\n<\/div>\n\n","protected":false},"excerpt":{"rendered":"<p>CUET PG: Structure, Replication, Diseases\u00a0 of Prions and Viroids Prions and Viroids are important non-cellular infectious agents for CUET PG. They are frequently asked questions in life science entrance examinations. Prions and Viroids. Prions are infectious protein particles that cause neurodegenerative diseases in animals and humans, and viroids are small circular RNA molecules that infect [&hellip;]<\/p>\n","protected":false},"author":15,"featured_media":19695,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":"","rank_math_seo_score":85},"categories":[30],"tags":[2923,556,15891,15892,15893,2922],"class_list":["post-19672","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-cuet-pg","tag-competitive-exams","tag-cuet-pg-vedprep","tag-prions-and-viroids-for-cuet-pg","tag-prions-and-viroids-for-cuet-pg-notes","tag-prions-and-viroids-for-cuet-pg-questions","tag-vedprep","entry","has-media"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.vedprep.com\/exams\/wp-json\/wp\/v2\/posts\/19672","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.vedprep.com\/exams\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.vedprep.com\/exams\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.vedprep.com\/exams\/wp-json\/wp\/v2\/users\/15"}],"replies":[{"embeddable":true,"href":"https:\/\/www.vedprep.com\/exams\/wp-json\/wp\/v2\/comments?post=19672"}],"version-history":[{"count":2,"href":"https:\/\/www.vedprep.com\/exams\/wp-json\/wp\/v2\/posts\/19672\/revisions"}],"predecessor-version":[{"id":19720,"href":"https:\/\/www.vedprep.com\/exams\/wp-json\/wp\/v2\/posts\/19672\/revisions\/19720"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.vedprep.com\/exams\/wp-json\/wp\/v2\/media\/19695"}],"wp:attachment":[{"href":"https:\/\/www.vedprep.com\/exams\/wp-json\/wp\/v2\/media?parent=19672"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vedprep.com\/exams\/wp-json\/wp\/v2\/categories?post=19672"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vedprep.com\/exams\/wp-json\/wp\/v2\/tags?post=19672"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}