Selected MCQ

Current Question
Which assay would you use to detect and quantify a specific DNA sequence in a sample?
  • A. ELISA
  • B. Southern blot
  • C. Western blot
  • D. Gram staining
Correct Answer: B
Explanation:
A Southern blot uses a DNA probe to hybridize with a specific DNA sequence immobilized on a membrane, allowing detection of that sequence in the sample.
Related Question 1
In Southern blotting, what type of probe is used to detect specific DNA sequences?
  • A. DNA probe labeled with a reporter
  • B. RNA probe labeled with a reporter
  • C. Protein probe labeled with antibody
  • D. Carbohydrate probe
Correct Answer: A
Explanation:
Southern blot uses a labeled single-stranded DNA (or RNA) probe complementary to the target DNA sequence, hybridizing to it on the membrane.
Related Question 2
In the CRISPR-Cas9 system, which component confers sequence specificity to target DNA?
  • A. Cas9 enzyme
  • B. Guide RNA (gRNA)
  • C. PAM sequence
  • D. DNA ligase
Correct Answer: B
Explanation:
The guide RNA (gRNA) base-pairs with the target DNA sequence, directing Cas9 to the specific genomic locus, where Cas9 then induces a double-strand break.
Related Question 3
What is the fundamental unit of heredity that occupies a specific locus on a chromosome?
  • A. Base pair
  • B. Gene
  • C. Chromatin
  • D. Nucleotide
Correct Answer: B
Explanation:
A gene is the hereditary unit at a chromosome locus. It consists of DNA sequences encoding a functional product (RNA or protein).
Related Question 4
Which plasmid-based technique is used to enrich and detect low-abundance mRNAs by reverse transcription into cDNA?
  • A. RFLP analysis
  • B. Northern blotting
  • C. RT-PCR (reverse-transcription PCR)
  • D. Affinity chromatography
Correct Answer: C
Explanation:
RT-PCR involves reverse-transcribing RNA to cDNA and then amplifying specific sequences by PCR. It is very sensitive for detecting low-abundance transcripts.
Related Question 5
In Western blotting, proteins are typically detected using:
  • A. DNA probes
  • B. RNA probes
  • C. Enzyme-linked antibodies
  • D. Radioactive amino acids
Correct Answer: C
Explanation:
Western blot uses antibodies (often enzyme-linked) that bind specific proteins on the membrane, allowing visualization via a colorimetric or chemiluminescent reaction.