science

Nijmegen breakage syndrome

Nijmegen breakage syndrome 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 Nijmegen breakage syndrome rather than just read about it. In short: Nijmegen breakage syndrome (NBS) is a rare autosomal recessive congenital disorder causing chromosomal instability, probably as a result of a defect in the double Holliday junction DNA repair mechanism and/or the synthesis dependent strand annealing mechanism for repairing double strand breaks in DNA (see Homologous recombination). NBS1 codes for a protein (nibrin) that has two major functions: (1) to stop the cell…

Key takeaways

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

Reference excerpt

Nijmegen breakage syndrome (NBS) is a rare autosomal recessive congenital disorder causing chromosomal instability, probably as a result of a defect in the double Holliday junction DNA repair mechanism and/or the synthesis dependent strand annealing mechanism for repairing double strand breaks in DNA (see Homologous recombination). NBS1 codes for a protein (nibrin) that has two major functions: (1) to stop the cell cycle in the S phase, when there are errors in the cell DNA (2) to interact with FANCD2 that can activate the BRCA1/BRCA2 pathway of DNA repair. This explains why mutations in the NBS1 gene lead to higher levels of cancer (see Fanconi anemia, Cockayne syndrome). The name derives from the Dutch city Nijmegen, where the condition was first described. Most people with NBS have West Slavic origins. The largest number of them live in Poland.

Presentation It is characterized by microcephaly, a distinct facial appearance, short stature, immunodeficiency, radiation sensitivity and a strong predisposition to lymphoid malignancy. NBS is caused by a mutation in the NBS1 gene. Unsurprisingly, many of the features are similar to ataxia telangiectasia (AT) and this syndrome was sometimes termed AT-variant 1, as the protein mutated in AT, ATM, interacts with the MRE11/RAD50/NBS1 (MRN) complex. Other syndromes with clinical features similar to Nijmegen Breakage Syndrome include RAD50 deficiency and Cernunnos/NHEJ deficiency.

Cause NBS is caused by a mutation in the NBS1 gene, located at human chromosome 8q21. The disease is inherited in an autosomal recessive manner. This means the defective gene responsible for the disorder is located on an autosome (chromosome 8 is an autosome), and two copies of the defective gene (one inherited from each parent) are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder. Two adult siblings, both heterozygous for two particular NBS1 nonsense mutations displayed cellular sensitivity to radiation, chromosome instability and fertility defects, but not the developmental defects that are typically found in other NBS patients. These individuals appear to be primarily defective in homologous recombination, a process that accurately repairs double-strand breaks, both in somatic cells and during meiosis.

Treatment There is no treatment for NBS; however, in those with agammaglobulinemia, intravenous immunoglobulin may be started. Prophylactic antibiotics are considered to prevent urinary tract infections as those with NBS often have congenital kidney malformations. In the treatment of malignancies, radiation therapy, alkylating antineoplastic agents, and epipodophyllotoxins are not used, and methotrexate can be used only with caution; the dose should be limited. Bone marrow transplants and hematopoietic stem cell transplants are also considered in the treatment of NBS. The supplementation of vitamin E is also recommended. A ventriculoperitoneal shunt can be placed in patients with hydrocephalus, and surgical intervention for congenital deformities is also attempted.

Prognosis A review from 2000 stated that life expectancy was reduced because of a tendency to develop cancer relatively early as well as deaths due to infections related to immunodeficiency.

References

External links

nijmegen at NIH/UW GeneTests Nijmegen Breakage Syndrome at NIH's Office of Rare Diseases

Illustrations

Worked examples

Example 1 — a first encounter with Nijmegen breakage syndrome

Start with the simplest possible case. Write down what Nijmegen breakage syndrome 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 Nijmegen breakage syndrome 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 Nijmegen breakage syndrome 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 Nijmegen breakage syndrome

In research: Nijmegen breakage syndrome 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 Nijmegen breakage syndrome 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: Nijmegen breakage syndrome is common in secondary-school and first-year university syllabi. It links to neighbouring topics Autosomal recessive disorders, Chromosome instability syndromes, DNA replication and repair-deficiency disorders, so understanding it makes those chapters shorter.
In everyday life: Look for Nijmegen breakage syndrome 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 Nijmegen breakage syndrome in 20 minutes

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

Frequently asked questions

What is Nijmegen breakage syndrome in simple terms?

Why does Nijmegen breakage syndrome 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 Nijmegen breakage syndrome?

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 Nijmegen breakage syndrome.