chemistry

PUC19

PUC19 is a chemistry 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 PUC19 rather than just read about it. In short: pUC19 is one of a series of plasmid cloning vectors designed by Joachim Messing and co-workers. The designation "pUC" is derived from the classical "p" prefix (denoting "plasmid") and the abbreviation for the University of California, where early work on the plasmid series had been conducted.

Key takeaways

PUC19 belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect PUC19 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of PUC19 from memory before moving on to harder problems.

Reference excerpt

pUC19 is one of a series of plasmid cloning vectors designed by Joachim Messing and co-workers. The designation "pUC" is derived from the classical "p" prefix (denoting "plasmid") and the abbreviation for the University of California, where early work on the plasmid series had been conducted. The pUC plasmids are all circular double stranded DNA about 2700 base pairs in length. The pUC plasmids are some of the most widely used cloning vectors. This is in part because cells that have successfully been transformed can be easily distinguished from those that have not based on color differences of colonies. pUC18 is similar to pUC19, but the multiple cloning site (MCS) region is reversed.

Features

pUC19 encodes the α-peptide of β-galactosidase (lacZ) gene of E. coli. This allows for blue–white screening when used with host strains containing the lacZDM15 mutation (e.g. E. coli JM109, DH5α and XL1-Blue strains). These strains produces only the C-terminal portion of lacZ, also known as the β-polypeptide. If pUC19 is inserted into one of these strains and grown the presence of IPTG, the bacteria will synthesise both fragments of the enzyme. Both the fragments can together hydrolyse X-gal (5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside) and form blue colonies when grown on media where it is supplemented. The multiple cloning site (MCS) of pUC19 is located within the lacZ gene. Insertion of DNA into the MCS causes insertional inactivation of the α-peptide gene, which prevents intra-allelic complementation. Thus, as cells containing recombinant plasmids will not produce a functional form of β-galactosidase, they will appear as white colonies which can be distinguished from non-recombinant cells, which are blue. In addition to β-galactosidase, pUC19 also encodes for an ampicillin resistance gene (ampR), via a β-lactamase enzyme that functions by degrading ampicillin and reducing its toxicity to the host. Cells which have been successfully transformed with pUC19 can be differentiated from cells which have not by growing them on media with ampicillin. Only the cells with the plasmid containing ampR will survive. The origin of replication (ori) is derived from the plasmid pMB1. pUC19 is a high copy number plasmid. The high copy number is a result of the lack of the rop gene and a single point mutation in the ori.

Use in research Due to its extensive use as a cloning vector in research and industry, pUC19 is frequently used in research as a model plasmid. For example, biophysical studies on its naturally supercoiled state have determined its radius of gyration to be 65.6 nm and its Stokes radius to be 43.6 nm. Reference samples of this plasmid are maintained by public biological resource centers, such as BCCM/GeneCorner.

See also Vector (molecular biology) Antibiotic resistance pBLU

References

External links Sequence of pUC19 pUC19 Features, sequence and physical samples

Illustrations

Worked examples

Example 1 — a first encounter with PUC19

Start with the simplest possible case. Write down what PUC19 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, 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 PUC19 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 PUC19 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 PUC19

In research: PUC19 appears in chemistry 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 PUC19 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: PUC19 is common in secondary-school and first-year university syllabi. It links to neighbouring topics DNA mobile genetic elements, Molecular biology techniques, Plasmids, so understanding it makes those chapters shorter.
In everyday life: Look for PUC19 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 PUC19 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what PUC19 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 PUC19 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is PUC19 in simple terms?

Why does PUC19 matter?

Because it connects several chemistry 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 PUC19?

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 PUC19.