Which technique is NOT appropriate for analyzing which alleles are present in DNA samples from a genetic cross?

• A. NMR spectroscopy
• B. PCR
• C. Agarose gel electrophoresis
• D. Restriction digestion

Answer: (A)

Understanding which alleles are present in DNA from a genetic cross relies on methods that reveal DNA sequence or fragment size. PCR amplifies a specific region so you have enough material to examine, and it can be paired with assays that distinguish alleles. Agarose gel electrophoresis then separates DNA fragments by size, letting you see different allele patterns based on how long the amplified or digested pieces are. Restriction digestion uses enzymes that cut at particular DNA sequences, producing a pattern of fragments that varies with the allele and can be visualized on a gel. NMR spectroscopy, by contrast, analyzes the structure of molecules at the atomic level. While powerful for determining three-dimensional structures of small molecules or purified biomolecules, it does not readily identify specific DNA sequences or differentiate alleles in a mixed DNA sample, and it requires large amounts of pure material with complex interpretation. Because it cannot practically reveal which alleles are present, it isn’t appropriate for analyzing alleles in DNA from a genetic cross.