The enzyme that synthesizes a DNA copy from an RNA template in retroviruses is:
A. Helicase
B. RNA polymerase
C. Reverse transcriptase
D. DNA polymerase
Answer: Option C
Solution (By JKSSB Mock Tests)
Reverse transcriptase is an enzyme unique to retroviruses that transcribes single-stranded RNA into double-stranded DNA (cDNA). This DNA integrates into the host genome. DNA polymerase synthesizes DNA from DNA, RNA polymerase from DNA. Reverse transcriptase is used in RT-PCR and cDNA synthesis.
Explanation:
The nephron is the microscopic structural and functional unit that filters blood and forms urine. It consists of the renal corpuscle (glomerulus + Bowman's capsule) and tubules. Alveoli are lung units, neurons are nerve cells, hepatocytes are liver cells. Each kidney contains about one million nephrons.
Explanation:
Primary consumers are herbivores that feed directly on producers (plants). Grasshopper feeds on grass/plants, thus a primary consumer. Lion and eagle are secondary/tertiary consumers (carnivores). Fungi are decomposers. In a food chain: Grass (producer) → Grasshopper (primary consumer) → Frog (secondary consumer) → Snake (tertiary consumer) → Eagle (quaternary consumer). Energy flows unidirectionally.
Explanation:
Simple columnar epithelium lines the stomach, intestines, and gallbladder, and functions in secretion and absorption. It often has microvilli (brush border) or goblet cells. Squamous epithelium lines alveoli and blood vessels, cuboidal kidney tubules.
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