Which of the following is NOT a genotypic method for determining relatedness between microorganisms?

• A. DNA-DNA hybridization
• B. Gram staining
• C. 16S rRNA gene sequencing
• D. Polymerase chain reaction (PCR)

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the difference between genotypic and phenotypic methods. Genotypic methods analyze the genetic material (DNA or RNA) of microorganisms to determine relatedness, while phenotypic methods assess observable characteristics such as morphology or staining properties.
2. Step 2: Review each option to classify it as genotypic or phenotypic. DNA-DNA hybridization involves comparing DNA sequences, so it is a genotypic method.
3. Step 3: 16S rRNA gene sequencing analyzes the sequence of a specific gene in the ribosomal RNA, which is a genotypic approach to determine evolutionary relationships.
4. Step 4: Polymerase chain reaction (PCR) amplifies specific DNA sequences, allowing for genotypic analysis of microorganisms.
5. Step 5: Gram staining is a phenotypic method that differentiates bacteria based on cell wall properties and staining characteristics, not based on genetic material, so it is NOT a genotypic method.