The process that introduces new genetic variation into a population is:
A. Genetic drift
B. Mutation
C. Gene flow
D. Natural selection
Answer: Option B
Solution (By JKSSB Mock Tests)
Mutations are random changes in DNA sequence that create new alleles, serving as the ultimate source of genetic variation. Natural selection, genetic drift, and gene flow act on existing variation but do not create new alleles. Mutations can be beneficial, neutral, or deleterious, and are essential for evolution.
Explanation:
Folate (B₉) and vitamin B₁₂ are required for DNA synthesis. Deficiency leads to impaired cell division in bone marrow, producing large, immature erythrocytes (megaloblasts), causing megaloblastic anemia. Iron deficiency causes microcytic anemia.
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.
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