Selected MCQ

Current Question
Two genes exhibit a recombination frequency of 20% in genetic crosses. Which statement is most accurate?
  • A. The genes are likely on different chromosomes
  • B. The genes are roughly 20 map units apart on the same chromosome
  • C. The genes are so far apart that they assort independently
  • D. The genes are allelic variants of each other
Correct Answer: B
Explanation:
A recombination frequency of 20% indicates that the genes are linked (~20 centimorgans apart) on the same chromosome and not assorting completely independently.
Related Question 1
Which term describes genes that are located on the same chromosome and inherited together more often than by chance?
  • A. Linked genes
  • B. Epistatic genes
  • C. Polygenic genes
  • D. Independent genes
Correct Answer: A
Explanation:
Linked genes are near each other on the same chromosome. They tend to be inherited together, and their recombination frequency is less than 50%.
Related Question 2
Genetically modified crops containing the Bt (Bacillus thuringiensis) toxin gene are resistant to:
  • A. Herbicides
  • B. Insect pests
  • C. Drought
  • D. Viral infection
Correct Answer: B
Explanation:
The Bt gene encodes an insecticidal protein. Plants expressing Bt produce a toxin that targets specific insect pests, providing built-in insect resistance.
Related Question 3
Golden rice has been genetically engineered to produce which nutrient precursor?
  • A. Vitamin C
  • B. Beta-carotene (provitamin A)
  • C. Vitamin E
  • D. Folic acid
Correct Answer: B
Explanation:
Golden rice contains genes for beta-carotene biosynthesis, which is a precursor of vitamin A, to help alleviate vitamin A deficiency.
Related Question 4
Inheritance of human height, which is influenced by many genes and environmental factors, is an example of:
  • A. Codominance
  • B. Polygenic inheritance
  • C. Pleiotropy
  • D. Autosomal dominance
Correct Answer: B
Explanation:
Height is a quantitative trait determined by multiple genes (polygenes) and the environment, consistent with polygenic inheritance.
Related Question 5
In a pedigree, if two unaffected parents have an affected child, the trait is most likely:
  • A. Autosomal dominant
  • B. Autosomal recessive
  • C. X-linked dominant
  • D. X-linked recessive
Correct Answer: B
Explanation:
Autosomal recessive traits can skip generations. Two carriers (phenotypically normal) can produce an affected child (25% chance).