Semotivirus

Key takeaways

Semotivirus belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Semotivirus to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Semotivirus from memory before moving on to harder problems.

Reference excerpt

Semotivirus is the only genus of viruses in the family Belpaoviridae (formerly included in the family Metaviridae). Species exist as retrotransposons in a eukaryotic host's genome. BEL/pao transposons are only found in animals. Semotivirus is the only genus currently recognized, the genus description corresponds to the family, Belpaoviridae description.

Classification The lone genus in the family, Semotivirus, was formerly included in the Metaviridae family but was removed due to its paraphyletic relationship to other Metaviridae genera. There is a good chance that more species and genera will be added to the family Belpaoviridae in the future, given the diversity of belpaovirids that is already recognized. The Pol domain order of the families Belpaoviridae, Metaviridae, and Retroviridae is the same within the order Ortervirales, however the integrase is either lacking in the case of the Caulimoviridae or positioned upstream of the protease domain in the case of the Pseudoviridae. The genus is made up of long terminal repeat (LTR) retrotransposons, also referred to as metazoan-infecting reverse transcriptase viruses.

Composition The genomic arrangement of members of the Belpaoviridae family is similar to that of long terminal repeat (LTR) retrotransposons of the Metaviridae family. The entire genome is 4.2–10 kb, and one to three genes (pol, env, and gag) are flanked by LTRs of 0.2–1.2 kb. A non-coding region that represents the initial segment of the reverse-transcribed genome is located downstream of the 5′-LTR. This is followed by an 18 nt primer-binding site that is complementary to a certain area inside the 3′-end of a host tRNAArg or a tRNAGly. Priming the synthesis of the proviral DNA strand is a polypurine tract of approximately 10 nt located upstream of the 3′-LTR. Gag and Pol polyproteins can be encoded by one continuous gene or by two overlapping genes. These genes encode the capsid and nucleocapsid domains, as well as the protease, reverse transcriptase (RT), ribonuclease H, and integrase domains.

Replication Few information is known about the virion morphology of belpaovirids. The virion morphology of semotivirus is poorly understood. However, belpaovirids most likely replicate by forming virus-like particles (VLPs), just like retrovirids, metavirids, and pseudovirids do, since they encode a Gag polyprotein with nucleocapsid and capsid protein domains homologous to those of other members of the order Ortervirales. An env-like gene is present in certain belpaovirids, however its exact role is still unknown. Although the details of replication are not well known, it is thought to resemble that of members of the Metaviridae family, in which RT mediates the conversion of a full transcript into a dsDNA that is incorporated into the host genome by the integrase protein. After the integrated provirus has been transcribed by the host RNA polymerase II, new virus RNAs are created, which the matching host enzymes cap and polyadenylate. Once in the host cell's cytoplasm, these fresh viral RNAs are translated into immature VLPs by Gag and Pol. VLP maturation is the end outcome of the viral protease's proteolytic processing of the polyproteins. The new viral RNAs are then reverse-transcribed by RT into dsDNA molecules, which are then sent back to the nucleus and inserted into fresh locations within the host cell genome. RT: Reverse Transcripase. VLPS: Virus-Like Particle. LTRs: Long Terminal Repeat.

Species

The genus contains the following species, listed by scientific name and followed by their common names:

Semotivirus beldrosophilae, Drosophila melanogaster Bel virus Semotivirus certredecimum, Caenorhabditis elegans Cer13 virus Semotivirus maxdrosophilae, Drosophila semotivirus Max Semotivirus mooseanophelae, Anopheles gambiae Moose virus Semotivirus ninjadrosophilae, Drosophila simulans Ninja virus Semotivirus paobombycis, Bombyx mori Pao virus Semotivirus roodrosophilae, Drosophila melanogaster Roo virus Semotivirus sinbadschistosomae, Schistosoma semotivirus Sinbad Semotivirus suzutakifugu, Takifugu rubripes Suzu virus Semotivirus tamyantheraeae, Antheraea semotivirus Tamy Semotivirus tasascaridis, Ascaris lumbricoides Tas virus

References

Frame IG, Cutfield JF, Poulter RTM (2001) New BEL-like LTR-retrotransposons in Fugu rubripes, Caenorhabditis elegans, and Drosophila melanogaster. Gene 263(1–2):219–230

External links "Metaviridae". NCBI Taxonomy Browser. 186665. ICTVdB Index of Viruses Descriptions of Plant Viruses Data related to Semotivirus at Wikispecies

Worked examples

Example 1 — a first encounter with Semotivirus

Start with the simplest possible case. Write down what Semotivirus claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Semotivirus before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Semotivirus ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Semotivirus

In research: Semotivirus appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Semotivirus in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Semotivirus is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ortervirales, RNA reverse-transcribing viruses, Virus genera, so understanding it makes those chapters shorter.
In everyday life: Look for Semotivirus outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Semotivirus in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Semotivirus means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Semotivirus out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Semotivirus in simple terms?

Semotivirus is the only genus of viruses in the family Belpaoviridae (formerly included in the family Metaviridae). Species exist as retrotransposons in a eukaryotic host's genome.

Why does Semotivirus matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Semotivirus?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Semotivirus.