BSc Third Year (Sem 5 & 6) Zoology – Daily Revision MCQ (English Medium)
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In Mendel's dihybrid cross (e.g. round-yellow × wrinkled-green), what is the phenotypic ratio in the F2 generation?
Chapter 1: Mendelian Genetics and Linkage
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Answer: B. 9 : 3 : 3 : 1
Two independently assorting gene pairs give (3 : 1) × (3 : 1) = 9 : 3 : 3 : 1 in F2; 1 : 1 : 1 : 1 is the dihybrid test-cross ratio.In a population in Hardy–Weinberg equilibrium, 16% of individuals show the recessive phenotype (aa). What is the frequency of heterozygotes (Aa)?
Chapter 3: Population Genetics and Hardy–Weinberg Law
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Answer: D. 0.48
q² = 0.16, so q = 0.4 and p = 0.6; heterozygotes = 2pq = 2 × 0.6 × 0.4 = 0.48.Insulin is secreted by which cells of the islets of Langerhans?
Chapter 7: Endocrine System
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Answer: A. Beta (β) cells
β-cells secrete insulin, α-cells secrete glucagon, δ-cells secrete somatostatin; acinar cells make digestive enzymes.The resting membrane potential of a typical neuron is approximately:
Chapter 8: Nerve Impulse and Synaptic Transmission
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Answer: C. −70 mV
At rest the inside of the axon is negative, about −70 mV, maintained mainly by K⁺ leakage and the Na⁺/K⁺ pump; +30 mV is near the peak of an action potential.According to the sliding filament theory, which part of the sarcomere keeps the same length during muscle contraction?
Chapter 9: Muscle Structure and Contraction
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Answer: B. A band
Actin slides over myosin, so the I band and H zone shorten and the sarcomere shortens, but the A band (length of the myosin filaments) stays constant.Who proved experimentally, using ¹⁵N and ¹⁴N, that DNA replication is semiconservative?
Chapter 12: DNA Replication
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Answer: A. Meselson and Stahl
Meselson and Stahl (1958) grew E. coli in ¹⁵N then ¹⁴N and found hybrid-density DNA, showing each new DNA keeps one old strand.The start codon AUG codes for which amino acid?
Chapter 13: Protein Synthesis: Transcription and Translation
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Answer: D. Methionine
AUG is the initiation codon and codes for methionine (formyl-methionine in bacteria).In the lac operon of E. coli, the repressor protein is inactivated when it binds to:
Chapter 14: Gene Regulation: The Lac Operon
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Answer: C. Allolactose
Allolactose (formed from lactose) is the inducer: it binds the lac repressor so the repressor leaves the operator; cAMP binds CAP, not the repressor.What is the intermediate host of the pork tapeworm, Taenia solium?
Chapter 16: Helminth Parasites of Man
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Answer: A. Pig
Man is the definitive host and the pig is the intermediate host of Taenia solium; cattle are the intermediate host of Taenia saginata.What is the scientific name of the mulberry silkworm?
Chapter 17: Sericulture
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Answer: D. Bombyx mori
Bombyx mori feeds on mulberry leaves; A. mylitta gives tasar, P. ricini gives eri, and A. assamensis gives muga silk.
BSc Third Year (Sem 5 & 6): MCQ in other subjects
All questions are written by PadhaiNotes in our own words from the common syllabus of Maharashtra universities (NEP). Your own university's syllabus may differ a little.