जीव विज्ञान – Biology MCQ
जीव विज्ञान – कृषि/वन प्रवेश
Biology · Agriculture, Veterinary & Forestry Entrance · ८४० प्रश्न
८४० प्रश्न उपलब्ध। मोड छान्नुहोस्:
जीव विज्ञान: प्रश्न र उत्तर
सही लागेको विकल्पमा थिच्नुहोस्। सही भए हरियो, गलत भए रातो देखिन्छ; ३ सेकेन्डपछि सही उत्तर र व्याख्या देखिन्छ।
सही: ० / ०
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A woman who is a carrier of haemophilia marries a normal man. What is the probability that any son of theirs will be haemophilic?
सही उत्तर: क) 1/2
Sons receive their X from the mother; the carrier mother (XᴴXʰ) passes Xʰ to half of her sons, so each son has a 1/2 chance.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Both parents are normally pigmented but are carriers (heterozygous) of the recessive allele for albinism. What is the probability that their child will be albino?
सही उत्तर: घ) 1/4
Aa × Aa gives AA : Aa : aa in the ratio 1 : 2 : 1, so the chance of an aa (albino) child is 1/4.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the F2 generation of a Mendelian dihybrid cross (AaBb × AaBb), how many different genotypes are produced?
सही उत्तर: ख) 9
Each gene gives 3 genotypes (AA, Aa, aa), so the dihybrid F2 has 3 × 3 = 9 genotypes, though only 4 phenotypes.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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How many different types of gametes can be produced by an individual of genotype AaBbCc (genes assorting independently)?
सही उत्तर: ग) 8
Number of gamete types = 2^n where n is the number of heterozygous gene pairs; 2^3 = 8.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The F2 ratio of 15 : 1, as seen in the shape of the seed capsule of shepherd's purse (Capsella), is due to:
सही उत्तर: क) Duplicate dominant genes
With duplicate genes, a dominant allele of either gene gives the same phenotype, so only the double recessive (1/16) differs.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A 12 : 3 : 1 phenotypic ratio in the F2 of a dihybrid cross, as for fruit colour in summer squash, indicates:
सही उत्तर: ग) Dominant epistasis
In dominant epistasis one dominant allele masks the other gene, merging two classes of the 9 : 3 : 3 : 1 ratio into 12.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The 5' cap added to eukaryotic mRNA during processing is:
सही उत्तर: ग) 7-methylguanosine
Capping adds a 7-methylguanosine to the 5' end, protecting the mRNA and helping ribosome binding; the poly-A tail is added at the 3' end.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A point mutation that changes an amino-acid codon into a stop codon is called a:
सही उत्तर: घ) Nonsense mutation
A nonsense mutation creates a premature stop codon (UAA, UAG or UGA), producing a shortened polypeptide.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The first codon to be deciphered, by Nirenberg and Matthaei using a synthetic poly-U mRNA, was UUU, which codes for:
सही उत्तर: घ) Phenylalanine
Poly-U RNA in a cell-free system produced polyphenylalanine, showing that UUU codes for phenylalanine.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The 'central dogma' of molecular biology (DNA → RNA → protein) was proposed by:
सही उत्तर: ख) Francis Crick
Francis Crick stated the central dogma in 1958, describing the one-way flow of genetic information from DNA to RNA to protein.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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