Which of the following is an example of a chemical mutagen?
A. Nitrous acid
B. X-rays
C. UV radiation
D. Gamma rays
Answer: Option A
Solution (By JKSSB Mock Tests)
Nitrous acid (HNO₂) is a chemical mutagen that can deaminate bases (e.g., cytosine to uracil), causing base-pair changes and mutations. X-rays, UV radiation, and gamma rays are physical mutagens (ionizing and non-ionizing radiation). Chemical mutagens include base analogs, alkylating agents, and intercalating agents. Mutagens increase the rate of mutations beyond natural levels.
Explanation:
The man's genotype is Iᴬ Iᴮ (AB) and the woman's genotype is ii (O). Gametes: man produces Iᴬ or Iᴮ, woman produces i only. Offspring: Iᴬ i (blood group A) and Iᴮ i (blood group B). Thus only A and B blood groups are possible. No AB (requires both Iᴬ and Iᴮ) or O (requires ii) children can be produced. This illustrates co-dominance and multiple alleles.
Explanation:
An action potential is initiated when a stimulus causes the membrane potential to reach a threshold. This opens voltage-gated sodium channels, leading to a rapid influx of sodium ions (Na+) into the neuron. This makes the inside of the cell positively charged relative to the outside, a process called depolarization. Repolarization follows with the efflux of K+ ions.
Explanation:
The diaphragm is a dome-shaped skeletal muscle that contracts during inspiration, flattening and increasing thoracic volume. The external intercostal muscles assist.
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