Which of the following is a defining characteristic of meiosis?
A. Produces identical daughter cells
B. Crossing over occurs
C. Produces diploid cells
D. Involves one division
Answer: Option B
Solution (By JKExamLibrary)
Meiosis is characterized by two successive divisions producing haploid gametes, and involves genetic recombination through crossing over during prophase I. Mitosis produces identical diploid cells with one division. Crossing over and independent assortment generate genetic variation. Therefore, crossing over is unique to meiosis.
Explanation:
Prokaryotic DNA is typically circular, double-stranded, and found in a nucleoid region without a nuclear membrane. It is not associated with histones (though some Archaea have histone-like proteins). Plasmids are extra-chromosomal DNA. Eukaryotic DNA is linear and complexed with histones. This difference is fundamental in cell classification.
Explanation:
In both mitochondria and chloroplasts, ATP synthase uses the energy stored in a proton gradient across a membrane (thylakoid membrane in chloroplasts, inner mitochondrial membrane) to drive the synthesis of ATP from ADP and Pi. This process is chemiosmosis, proposed by Peter Mitchell.
Explanation:
Bile is synthesized by hepatocytes of the liver and stored and concentrated in the gall bladder. It contains bile salts (sodium glycocholate and taurocholate) that emulsify fats, aiding lipase action. Bile also contains bile pigments (bilirubin, biliverdin) from hemoglobin breakdown. Pancreas secretes pancreatic juice with digestive enzymes. Gall bladder only stores bile, doesn't produce it.
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