The phenomenon where a single gene influences multiple phenotypic traits is called:
A. Epistasis
B. Pleiotropy
C. Polygenic inheritance
D. Codominance
Answer: Option B
Solution (By JKSSB Mock Tests)
Pleiotropy occurs when one gene affects multiple seemingly unrelated traits. Example: phenylketonuria (PKU) affects mental development, skin pigmentation, and musty odor. Marfan syndrome affects skeleton, eyes, and heart. Polygenic is many genes affecting one trait, epistasis is gene interaction, codominance is both alleles expressed.
Explanation:
Molecular oxygen (O₂) accepts electrons at the end of the electron transport chain, combining with protons to form water (metabolic water). Without oxygen, the chain backs up, stopping ATP production. This is why oxygen is vital for aerobic respiration. NAD⁺ and FAD are electron carriers, cytochrome c a component.
Explanation:
Photolysis of water occurs at the manganese cluster of photosystem II, releasing electrons, protons, and oxygen. The electrons replace those lost by P680. Photosystem I reduces NADP⁺. Cytochrome b6f transports electrons between the two photosystems. Thus, water splitting is a hallmark of PSII.
Explanation:
The double helix structure of DNA was elucidated by James Watson (an American biologist) and Francis Crick (a British physicist) in 1953 at the University of Cambridge. Their model was based on X-ray diffraction data produced by Rosalind Franklin and Maurice Wilkins. They proposed that DNA consists of two antiparallel strands held together by hydrogen bonds between complementary base pairs (A-T, G-C).
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