biology

Pax genes

Pax genes is a biology 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 Pax genes rather than just read about it. In short: In evolutionary developmental biology, Paired box (Pax) genes are a family of genes coding for tissue specific transcription factors containing an N-terminal paired domain and usually a partial, or in the case of four family members (PAX3, PAX4, PAX6 and PAX7), a complete homeodomain to the C-terminus. An octapeptide as well as a Pro-Ser-Thr-rich C terminus may also be present.

Key takeaways

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

Reference excerpt

In evolutionary developmental biology, Paired box (Pax) genes are a family of genes coding for tissue specific transcription factors containing an N-terminal paired domain and usually a partial, or in the case of four family members (PAX3, PAX4, PAX6 and PAX7), a complete homeodomain to the C-terminus. An octapeptide as well as a Pro-Ser-Thr-rich C terminus may also be present. Pax proteins are important in early animal development for the specification of specific tissues, as well as during epimorphic limb regeneration in animals capable of such. The paired domain was initially described in 1987 as the "paired box" in the Drosophila protein paired (prd; P06601).

Groups Within the mammalian family, there are four well defined groups of Pax genes.

Pax group 1 (Pax 1 and 9), Pax group 2 (Pax 2, 5 and 8), Pax group 3 (Pax 3 and 7) and Pax group 4 (Pax 4 and 6). Two more families, Pox-neuro and Pax-α/β, exist in basal bilaterian species. Orthologous genes exist throughout the Metazoa, including extensive study of the ectopic expression in Drosophila using murine Pax6. The two rounds of whole-genome duplications in vertebrate evolution is responsible for the creation of as many as 4 paralogs for each Pax protein.

Members PAX1 has been identified in mice with the development of vertebrate and embryo segmentation, and some evidence this is also true in humans. It transcribes a 440 amino acid protein from 4 exons and 1,323bps in humans. In the mouse Pax1 mutation has been linked to undulated mutant suffering from skeletal malformations. PAX2 has been identified with kidney and optic nerve development. It transcribes a 417 amino acid protein from 11 exons and 4,261 bps in humans. Mutation of PAX2 in humans has been associated with renal-coloboma syndrome as well as oligomeganephronia. PAX3 has been identified with ear, eye and facial development. It transcribes a 479 amino acid protein in humans. Mutations in it can cause Waardenburg syndrome. PAX3 is frequently expressed in melanomas and contributes to tumor cell survival. PAX4 has been identified with pancreatic islet beta cells. It transcribes a 350 amino acid protein from 9 exons and 2,010 bps in humans. Knockout mice lacking Pax4 expression fail to develop insulin-producing cells. Pax4 undergoes mutual reciprocal interaction with the transcription factor Arx to endow pancreatic endocrine cells with insulin and glucagon cells respectively PAX5 has been identified with neural and spermatogenesis development and b-cell differentiation. It transcribes a 391 amino acid protein from 10 exons and 3,644bps in humans. PAX6 (eyeless) is the most researched and appears throughout the literature as a "master control" gene for the development of eyes and sensory organs, certain neural and epidermal tissues as well as other homologous structures, usually derived from ectodermal tissues. PAX7 has been possibly associated with myogenesis. It transcribes a protein of 520 amino acids from 8 exons and 2,260bps in humans. PAX7 directs postnatal renewal and propagation of myogenic satellite cells but not for the specification. PAX8 has been associated with thyroid specific expression. It transcribes a protein of 451 amino acids from 11 exons and 2,526bps in humans. Pax8 loss-of-function mutant mice lack follicular cells of the thyroid gland. PAX9 has found to be associated with a number of organ and other skeletal developments, particularly teeth. It transcribes a protein of 341 amino acids from 4 exons and 1,644bps in humans.

See also Homeobox Evolutionary developmental biology Body plan SOX genes

References

Illustrations

Worked examples

Example 1 — a first encounter with Pax genes

Start with the simplest possible case. Write down what Pax genes 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 Pax genes 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 Pax genes 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 Pax genes

In research: Pax genes 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 Pax genes 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: Pax genes is common in secondary-school and first-year university syllabi. It links to neighbouring topics Developmental genes and proteins, Transcription factors, so understanding it makes those chapters shorter.
In everyday life: Look for Pax genes 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 Pax genes in 20 minutes

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

Frequently asked questions

What is Pax genes in simple terms?

Why does Pax genes 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 Pax genes?

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 Pax genes.