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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How many different genotypes are possible in the human ABO blood group system?
सही उत्तर: ग) 6
Three alleles (IA, IB, i) give n(n+1)/2 = 3 x 4 / 2 = 6 genotypes: IAIA, IAi, IBIB, IBi, IAIB and ii.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A cross between two yellow mice always gives yellow and non-yellow offspring in a 2 : 1 ratio. This is explained by:
सही उत्तर: ख) A lethal allele
The yellow allele is dominant for colour but recessive lethal; homozygous yellow embryos die, so the expected 1 : 2 : 1 becomes 2 : 1.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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An F2 ratio of 9 : 7 in a dihybrid cross, as seen in flower colour of sweet pea, is characteristic of:
सही उत्तर: ख) Complementary genes
With complementary genes both dominant alleles must be present for the trait, so 9 show it and the remaining 3 + 3 + 1 = 7 do not.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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A modified dihybrid F2 ratio of 9 : 3 : 4 indicates:
सही उत्तर: ख) Recessive epistasis
In recessive (supplementary) epistasis, the homozygous recessive of one gene masks the other gene, combining 3 + 1 classes into 4 (e.g. coat colour in mice).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Frederick Griffith's transformation experiment (1928) was performed on mice using the bacterium:
सही उत्तर: घ) Streptococcus pneumoniae
Griffith showed that heat-killed virulent (S) Streptococcus pneumoniae could transform live non-virulent (R) cells into the virulent form.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the Hershey-Chase experiment, the protein coat of the bacteriophage was labelled with:
सही उत्तर: ग) Radioactive sulphur (35S)
Proteins contain sulphur but no phosphorus, so 35S labelled the coat while 32P labelled the DNA; only 32P entered the bacteria.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The 'one gene - one enzyme' hypothesis, based on work with Neurospora, was proposed by:
सही उत्तर: क) Beadle and Tatum
George Beadle and Edward Tatum studied nutritional mutants of the mould Neurospora and concluded that each gene controls one enzyme.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The chromosomal theory of inheritance was put forward by:
सही उत्तर: क) Sutton and Boveri
Walter Sutton and Theodor Boveri noted that chromosome behaviour during meiosis parallels Mendel's factors and proposed that genes lie on chromosomes.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Linkage of genes was first demonstrated experimentally in Drosophila by:
सही उत्तर: ख) T.H. Morgan
Thomas Hunt Morgan's crosses with fruit flies showed that genes on the same chromosome tend to be inherited together (linkage).
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The protein part of a conjugated enzyme, without its cofactor, is called the:
सही उत्तर: ख) Apoenzyme
Apoenzyme (protein) + cofactor = holoenzyme; the apoenzyme alone is catalytically inactive.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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