nondisjunction
C2Technical / Academic
Definition
Meaning
The failure of paired chromosomes or chromatids to separate properly during cell division (meiosis or mitosis).
In genetics, an error in cell division that results in daughter cells with an abnormal number of chromosomes, which can lead to conditions like Down syndrome. Can be used metaphorically in non-biological contexts to describe a fundamental failure of separation or connection.
Linguistics
Semantic Notes
A highly specific term used primarily in genetics, cytology, and cell biology. It describes a process error, not a state. The word implies a deviation from the normal, expected event of 'disjunction' (separation).
Dialectal Variation
British vs American Usage
Differences
No significant lexical or spelling differences. Pronunciations differ slightly as indicated in IPA.
Connotations
Identical technical meaning. No regional connotative variation.
Frequency
Used with equal, very low frequency exclusively in biological/medical academic or technical contexts in both regions.
Vocabulary
Collocations
Grammar
Valency Patterns
Nondisjunction of [chromosome pair X]Nondisjunction occurs during [phase]Nondisjunction results in [aneuploidy/trisomy]Vocabulary
Synonyms
Neutral
Weak
Vocabulary
Antonyms
Usage
Context Usage
Business
Not used.
Academic
Core term in genetics and molecular biology papers, textbooks, and lectures.
Everyday
Virtually never used in everyday conversation.
Technical
The primary context. Used in lab reports, genetic counselling, cytology, and biomedical research.
Examples
By Part of Speech
verb
British English
- The homologous chromosomes can fail to disjoin, leading to aneuploidy.
- If the chromatids do not separate, they are said to have undergone nondisjunction.
American English
- The chromosome pair failed to disjoin during anaphase.
- Researchers observed the process where sister chromatids did not separate.
adjective
British English
- The nondisjunction event was confirmed by karyotype analysis.
- They studied cells with a nondisjunction phenotype.
American English
- The nondisjunction error occurred in meiosis I.
- A nondisjunction chromosome was identified.
Examples
By CEFR Level
- This word is not used at this level.
- This word is not typically used at this level.
- Scientists can sometimes see nondisjunction under a microscope.
- Down syndrome is often caused by a nondisjunction.
- Meiotic nondisjunction in the mother's gamete is a common cause of trisomy 21.
- The research paper investigated the molecular mechanisms that predispose oocytes to chromosome nondisjunction.
Learning
Memory Aids
Mnemonic
Think of a train junction where two tracks are supposed to separate (dis-junction). NONDISjunction is when they FAIL TO (NON-) SEPARATE (DISJUNCTION), causing a traffic jam of chromosomes.
Conceptual Metaphor
A TRAFFIC ACCIDENT AT A CELLULAR CROSSROADS: Chromosomes are like vehicles that must take separate exits at a junction; nondisjunction is the crash where they fail to split.
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Avoid literal translation as 'неразъединение'. The standard Russian biological term is 'нерасхождение' (chromosomes).
- Do not confuse with 'разрыв' (break) or 'мутация' (mutation); it is a specific process error, not a general break or change.
Common Mistakes
- Misspelling as 'non-disjunction' (hyphen is generally omitted in modern usage).
- Using it as a verb (e.g., 'The chromosomes nondisjunctioned'). The verb form is 'to fail to disjoin' or 'to undergo nondisjunction'.
- Confusing it with 'translocation' (where chromosomes exchange parts).
Practice
Quiz
In which process does nondisjunction occur?
FAQ
Frequently Asked Questions
Not exactly. While it leads to genetic abnormalities, it is specifically an error in the *process* of chromosome segregation during cell division, not a change in the DNA sequence itself.
Yes, it can occur in mitosis (body cell division) or meiosis (gamete formation). Mitotic nondisjunction leads to mosaicism, while meiotic nondisjunction affects all cells of the resulting offspring.
It produces daughter cells with an abnormal number of chromosomes (aneuploidy), such as one cell with an extra chromosome (trisomy) and another missing a chromosome (monosomy).
It explains the chromosomal origin of many genetic conditions (e.g., Down syndrome, Klinefelter syndrome) and is a key concept in prenatal genetic screening and counselling.