computer science

Webtag

Webtag is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Webtag rather than just read about it. In short: Webtag is an on-line bioinformatics tool providing oligonucleotide sequences (usually called tags or anchors) that are absent from a specified genome. These tags can be appended to gene specific primers for reverse transcriptase polymerase chain reaction (RT-PCR) experiments, circumventing genomic DNA contamination.

Key takeaways

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

Reference excerpt

Webtag is an on-line bioinformatics tool providing oligonucleotide sequences (usually called tags or anchors) that are absent from a specified genome. These tags can be appended to gene specific primers for reverse transcriptase polymerase chain reaction (RT-PCR) experiments, circumventing genomic DNA contamination.

Background RT-PCR is a technique used for the detection of even very low copy mRNA transcripts. The sensitivity of the technique also makes it susceptible to DNA contamination. Since PCR is unable to distinguish between cDNA targets and genomic DNA contamination, false positives and/or erroneous quantitative results are possible. In order to overcome genomic DNA contamination in transcriptional studies, reverse template-specific polymerase chain reaction, a modification of RT-PCR is used. The possibility of using tags whose sequences are not found in the genome further improves reverse specific polymerase chain reaction experiments. The use of anchors, or tags, in the 5' region of a gene specific primer or poly-T tail allows for RNA-specific amplification, and constitutes a viable strategy. Techniques such as RS-PCR and (EXACT) RT-PCR are based on the integration of such tags (unique sequences not present in genomic DNA) in the 5' end of the first strand cDNA, permitting RNA-specific amplification without loss of sensitivity.

Webtag This web based service builds on the Tagenerator tool, but is very fast because all tags are pre-generated and stored in a database. It is also a significant improvement since Webtag takes into account the interactions of the tag with the primers to be used in the experiment. Having it as a web based service also means that the molecular biologist doesn't have to download and install software with all the dependencies on their own computer. Webtag generates tags that combine genome absence with good priming properties for RT-PCR based experiments. The use of such tags will deliberately not result in PCR amplification of genomic DNA, permitting the exclusive amplification of cDNA, therefore circumventing the effects of genomic DNA contamination in an RNA sample.

References

External links Official webpage Tagenerator

Worked examples

Example 1 — a first encounter with Webtag

Start with the simplest possible case. Write down what Webtag claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, 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 Webtag 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 Webtag 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 Webtag

In research: Webtag appears in computer science 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 Webtag 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: Webtag is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bioinformatics, Bioinformatics software, so understanding it makes those chapters shorter.
In everyday life: Look for Webtag 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.

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How to study Webtag in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Webtag 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 Webtag out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Webtag in simple terms?

Why does Webtag matter?

Because it connects several computer science 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 Webtag?

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 Webtag.