Explanation:
Alexander Fleming discovered penicillin in 1928. Florey and Chain later purified it and demonstrated its therapeutic potential. Waksman discovered streptomycin. The discovery of penicillin revolutionized medicine.
Explanation:
During DNA replication, the lagging strand is synthesized discontinuously in short segments called Okazaki fragments. After the RNA primers are removed and replaced with DNA by DNA polymerase I, the fragments remain separated by nicks in the sugar-phosphate backbone. DNA ligase is the enzyme that catalyzes the formation of phosphodiester bonds between these fragments, sealing the nicks and creating a continuous DNA strand.
Explanation:
DNA is primarily located in the nucleus of eukaryotic cells. It contains deoxyribose (not ribose), is double-stranded, and adenine pairs with thymine. Thus, D is correct.
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