exonuclease
Very Low FrequencyScientific / Technical
Definition
Meaning
An enzyme that cleaves nucleotides one at a time from the end of a DNA or RNA molecule.
A specialized enzyme that removes nucleotides sequentially from the 3' or 5' end of a nucleic acid strand, playing crucial roles in DNA repair, proofreading, and RNA processing.
Linguistics
Semantic Notes
The term is almost exclusively used in molecular biology, genetics, and biochemistry. It denotes a specific direction of cleavage (3'→5' or 5'→3') and is often modified by prefixes (e.g., 'flap exonuclease').
Dialectal Variation
British vs American Usage
Differences
No significant lexical or semantic differences. Standard spelling is identical. Pronunciation differences follow general British/American patterns.
Connotations
No difference in connotation. Purely technical term.
Frequency
Equally rare and specialized in both dialects, confined to technical literature.
Vocabulary
Collocations
Grammar
Valency Patterns
The [enzyme name] acts as an exonuclease on [substrate].[Treatment] with exonuclease [process] the [DNA/RNA] fragments.The [mutation] abolishes the exonuclease activity of [protein].Vocabulary
Synonyms
Neutral
Weak
Vocabulary
Antonyms
Usage
Context Usage
Business
Not used.
Academic
Used in molecular biology, genetics, and biochemistry research papers and textbooks.
Everyday
Virtually never used.
Technical
Core term in protocols for DNA/RNA manipulation, sequencing, and repair studies.
Examples
By Part of Speech
adjective
British English
- The exonuclease activity was measured.
- An exonuclease-deficient mutant was generated.
American English
- The exonuclease function was assayed.
- An exonuclease domain was identified.
Examples
By CEFR Level
- Scientists use an exonuclease to remove unwanted DNA ends.
- This enzyme's exonuclease function helps correct DNA mistakes.
- The proofreading 3'→5' exonuclease activity of DNA polymerase III enhances replication fidelity.
- Following endonuclease cleavage, the resulting flap structure is processed by a specific flap exonuclease.
Learning
Memory Aids
Mnemonic
Think: EXO (exit/out) + NUCLEASE (cuts nucleic acids). It 'exits' nucleotides by cutting them off the end.
Conceptual Metaphor
A molecular 'editor's eraser' that removes letters (nucleotides) from the end of a sentence (DNA/RNA strand).
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Avoid confusing with 'эндонуклеаза' (endonuclease).
- Do not translate as 'экзонуклеаза' if a transliteration is required; the standard Russian term is 'экзонуклеаза'. Be aware of this direct borrowing.
Common Mistakes
- Misspelling as 'exonuclease' (dropping the 'e').
- Confusing its function with endonucleases (which cut internally).
- Using it as a general term for any DNA-cutting enzyme.
Practice
Quiz
What is the primary functional distinction between an exonuclease and an endonuclease?
FAQ
Frequently Asked Questions
No, exonucleases can act on both DNA and RNA substrates, depending on the specific enzyme.
Exonucleases are commonly used to degrade single-stranded DNA or RNA overhangs, or to create blunt ends from sticky ends in DNA cloning.
Yes, many DNA polymerases, for example, have an associated proofreading exonuclease domain that corrects errors during DNA synthesis.
In British English: /ˌɛksəʊˈnjuːklɪeɪz/ (eks-oh-NEW-klee-ays). In American English: /ˌɛksoʊˈnuːklɪeɪs/ (eks-oh-NOO-klee-ace).