166. Any DNA fragment can be used as a STS marker provided it fulfills one of the following conditions:
1. Multilocus nature
2. Single copy
3. Present in repeat regions
4. Telomeric region
Understanding STS Markers and Their Key Requirement
Sequence Tagged Sites (STS) are short, unique DNA sequences that occur only once in a genome and serve as landmarks in genetic and physical mapping. These markers are vital in genome projects, PCR assays, and gene localization.
What Makes a DNA Fragment Suitable as an STS Marker?
Among the choices:
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Multilocus nature
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Incorrect. Multilocus fragments are found in multiple locations, making them ambiguous in mapping.
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Single copy
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Correct. STS markers must be unique sequences, appearing only once in the genome, to ensure precise and reproducible identification.
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Present in repeat regions
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Incorrect. Repeats compromise specificity, which STS markers aim to provide.
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Telomeric region
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Incorrect. Location at telomeres doesn’t define an STS marker. It’s the uniqueness that matters.
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Why Single-Copy DNA Is Essential
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Specificity: Ensures that PCR primers amplify only one genomic location.
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Reliability: Essential for consistent results across individuals or species.
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Mapping Precision: Helps accurately anchor points on physical or genetic maps.
Correct Answer:
2. Single copy
Single-copy DNA fragments ensure specificity and utility in genetic mapping and are thus a prerequisite for any valid STS marker.
