The molecule that binds to the operator region of the lac operon to inhibit transcription is:
A. Inducer
B. Repressor protein
C. CAP protein
D. RNA polymerase
Answer: Option B
Solution (By JKSSB Mock Tests)
The lac repressor protein (product of lacI gene) binds to the operator sequence, preventing RNA polymerase from transcribing the structural genes. When lactose is present, allolactose (inducer) binds the repressor, causing it to release the operator, allowing transcription. This is negative regulation.
Explanation:
Natural passive immunity occurs when pre-formed antibodies are transferred naturally from one individual to another. During pregnancy, maternal antibodies (primarily IgG) cross the placenta to the fetus, providing temporary protection against diseases the mother is immune to. Colostrum (mother's milk) also provides IgA antibodies to the newborn.
Explanation:
Bacteria are prokaryotes with a single circular chromosome in a nucleoid region, without a nuclear membrane. They lack membrane-bound organelles like mitochondria. Their chromosomes are not linear; eukaryotes have linear chromosomes.
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