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).
Explanation:
The cell theory states that the cell is the fundamental unit of structure and function. Not all cells have a nucleus (prokaryotes), prokaryotes lack mitochondria, viruses are not cells.
Explanation:
The secondary oocyte is arrested in metaphase II of meiosis and is ovulated. Meiosis II is completed only when a sperm penetrates the oocyte, producing a mature ovum and a second polar body. If fertilization does not occur, the secondary oocyte degenerates. This ensures that the egg is only fully mature upon fertilization.
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