Selected MCQ

Current Question
In the ABO blood group, what blood type is expressed by an individual with genotype IᴬIᴮ?
  • A. Type A
  • B. Type B
  • C. Type AB
  • D. Type O
Correct Answer: C
Explanation:
Alleles Iᴬ and Iᴮ are codominant, so the IᴬIᴮ genotype produces both A and B antigens on red cells, yielding blood type AB.
Related Question 1
What is the genotype of a person with blood type O in the ABO system?
  • A. IᴬIᴬ or Iᴬi
  • B. IᴮIᴮ or Iᴮi
  • C. ii
  • D. IᴬIᴮ
Correct Answer: C
Explanation:
Type O blood has no A or B antigen and is genotypically ii (both alleles are the recessive i).
Related Question 2
A female exhibits an X-linked recessive trait. What must be true of her parents’ genotypes?
  • A. Her father must have the trait, and her mother must be at least a carrier
  • B. Both parents must be affected
  • C. Only her mother is affected
  • D. Either parent could have the trait independently
Correct Answer: A
Explanation:
For a daughter to be homozygous for an X-linked recessive allele, her father must have the allele (so he is affected) and her mother must carry at least one mutant X.
Related Question 3
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 4
Which of the following techniques compares short tandem repeat (STR) regions among individuals for identification?
  • A. Western blot
  • B. DNA microarray
  • C. DNA fingerprinting
  • D. Northern blot
Correct Answer: C
Explanation:
DNA fingerprinting analyzes highly polymorphic regions, especially STRs, to distinguish individuals (used in forensics and paternity testing).
Related Question 5
Down syndrome (trisomy 21) results in how many total chromosomes in a karyotype?
  • A. 45
  • B. 46
  • C. 47
  • D. 48
Correct Answer: C
Explanation:
Down syndrome is caused by an extra copy of chromosome 21. Humans normally have 46 chromosomes; trisomy adds one extra, making 47.