The scientist who discovered the penicillin-producing mold was:
A. Alexander Fleming
B. Louis Pasteur
C. Robert Koch
D. Joseph Lister
Answer: Option A
Solution (By JKSSB Mock Tests)
Alexander Fleming noticed in 1928 that a mold contaminant (Penicillium notatum) on a bacterial culture plate inhibited the growth of Staphylococcus aureus, leading to the discovery of penicillin, the first widely used antibiotic. Florey and Chain later purified it. Pasteur developed pasteurization.
Explanation:
Emil Fischer proposed the lock-and-key model in 1894 to explain enzyme specificity. Koshland modified it to induced fit. Krebs discovered the citric acid cycle, Mitchell chemiosmosis.
Explanation:
Hemoglobin is a red, iron-containing protein in red blood cells (erythrocytes) that reversibly binds oxygen to form oxyhemoglobin. Each molecule has four heme groups, each binding one O₂ molecule. Hemocyanin (copper-based) is found in some invertebrates. Myoglobin stores oxygen in muscles. Cytochromes are electron carriers in respiration. Hemoglobin also transports CO₂ as carbaminohemoglobin.
Explanation:
Incomplete dominance occurs when the phenotype of the heterozygote is an intermediate blend of the two homozygous phenotypes. In snapdragons, a cross between a homozygous red (RR) and homozygous white (rr) flower produces heterozygous pink (Rr) flowers. Neither allele is completely dominant over the other, resulting in a blended phenotype.
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