Section 3: Genetics, Cellular and Molecular Biology
CRISPR-Cas9 gene editing
Subtopic: Fundamentals of CRISPR-Cas9 gene editing
Question Statement:
Which of the following features help(s) in distinguishing alleles using restriction
fragment length polymorphism (RFLP)?
Options:
(A) Differences in the number of recognition sites for a given restriction enzyme
(B) Differences in the ability of alleles to undergo recombination
(C) Differences in the ability of alleles to undergo segregation
(D) Differences in the number of tandem repeats
Official Answer Key:
A;D
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2024 Q.46)**
**1. Governing Concept**:
- **Topic**: Molecular Genetics & Restriction Fragment Length Polymorphism (RFLP)
- **RFLP** detects variations in homologous DNA sequences that alter the distances between restriction sites:
1. **Single Nucleotide Polymorphisms (SNPs)**: Can create or abolish a specific palindrome recognition site for a restriction enzyme.
2. **Insertions or Deletions (Indels)**: Change the physical distance between two conserved flanking restriction enzyme cleavage sites.
- In both scenarios, digesting genomic DNA with restriction enzymes generates fragments of different lengths that separate as distinct bands on Southern blots or agarose gels.
**2. Option Analysis**:
- **Option (A) [Creation or elimination of a restriction enzyme recognition site] is CORRECT**: A point mutation in a restriction site prevents or allows cleavage, altering fragment size.
- **Option (B) [Differences in telomere length] is INCORRECT**: Telomeric length variation occurs through cellular aging and replication cycles, not diagnostic allele markers in RFLP.
- **Option (C) [Centromere position] is INCORRECT**: Affects chromosome karyotypic morphology, not localized restriction digest fragment lengths.
- **Option (D) [Insertion or deletion of DNA fragments between restriction sites] is CORRECT**: Directly alters the physical distance between flanking cleavage sites, producing polymorphic fragment sizes.
**3. Final Answer**:
- **Correct Options**: **A, D**
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