science

HaeIII

HaeIII is a 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 HaeIII rather than just read about it. In short: HaeIII is one of many restriction enzymes (endonucleases) a type of prokaryotic DNA that protects organisms from unknown, foreign DNA. It is a restriction enzyme used in molecular biology laboratories.

Key takeaways

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

Reference excerpt

HaeIII is one of many restriction enzymes (endonucleases) a type of prokaryotic DNA that protects organisms from unknown, foreign DNA. It is a restriction enzyme used in molecular biology laboratories. It was the third endonuclease to be isolated from the Haemophilus aegyptius bacteria. The enzyme's recognition site—the place where it cuts DNA molecules—is the GGCC nucleotide sequence which means it cleaves DNA at the site 5′-GG/CC-3. The recognition site is usually around 4-8 bps. This enzyme's gene has been sequenced and cloned. This is done to make DNA fragments in blunt ends. HaeIII is not effective for single stranded DNA cleavage.

Properties HaeIII has a molecular weight of 37126. After a 2-10-fold of HaeIII takes place, there is overdigestion of a DNA substrate. This results in 100% being cut, more than 50% of fragments being ligated, and more than 95% being recut. Heat inactivation comes at about 80 °C for 20 minutes. The locus of the HaeIII enzyme is on AF05137, and is linear with 957 base pairs.

History HaeIII along with other restriction enzymes were discovered in 1970 by Werner Arber and Matthew Meselson. The HaeIII methyltransferase also known as the MTase gene from Haemophilus aegyptius (recognition sequence: 5′-GGCC-3′) was made into Escherichia coli (E.coli) in the plasmid vector pBR322. The gene was extracted from a single EcoRI fragment and a single HindIII enzyme fragment. Clones carrying additional adjacent fragments were found to code for the HaeIII restriction enzyme.

Function The enzyme cleaves the DNA at the positions where the GGCC sequence is found. The cleavage occurs between the second and the third nucleotides (G and C). The resulting DNA fragments are known as restriction fragments. HaeIII cuts both strands of DNA in the same location, yielding restriction fragments with blunt ends. Heat denaturation occurs at 80°C after 20 minutes.

Methylase Haemophilus aegyptius also carries a methylase dubbed HaeIIIM (P20589) that methylates the internal cytosines in the GGCC sequence. It protects sequences from being cut by HaeIII, and forms a restriction modification system. HaeIII enzyme comes from an E. coli strain that carries the cloned HaeIII modification gene from Haemophilus aegyptius.

References

Illustrations

Worked examples

Example 1 — a first encounter with HaeIII

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

In research: HaeIII appears in 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 HaeIII 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: HaeIII is common in secondary-school and first-year university syllabi. It links to neighbouring topics EC 3.1 stubs, Restriction enzymes, so understanding it makes those chapters shorter.
In everyday life: Look for HaeIII 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 HaeIII in 20 minutes

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

Frequently asked questions

What is HaeIII in simple terms?

Why does HaeIII matter?

Because it connects several 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 HaeIII?

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 HaeIII.