Selected MCQ

Current Question
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 1
Nucleosomes are composed of DNA wrapped around an octamer of histones. How many base pairs of DNA are wrapped around one nucleosome core?
  • A. ~50 bp
  • B. ~146 bp
  • C. ~300 bp
  • D. ~10 bp
Correct Answer: B
Explanation:
About 146 base pairs of DNA wrap ~1.7 turns around the histone octamer (2 copies each of H2A, H2B, H3, H4) in a nucleosome core.
Related Question 2
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 3
Which of the following best describes polygenic inheritance?
  • A. One gene affects multiple traits (e.g., pleiotropy)
  • B. Many genes contribute to one trait (e.g., skin color)
  • C. A trait determined by genes only on the X chromosome
  • D. Inheritance of mitochondrial DNA
Correct Answer: B
Explanation:
Polygenic inheritance means multiple genes (often with additive effects) determine a single phenotype, such as height or skin color, producing continuous variation.
Related Question 4
Human insulin production by recombinant DNA technology was first achieved in:
  • A. Yeast cells
  • B. Bacterial cells
  • C. Mammalian cells
  • D. Plant cells
Correct Answer: B
Explanation:
The first human protein successfully produced by genetic engineering was insulin, expressed in genetically modified Escherichia coli bacteria.
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.