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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In eukaryotes, the precursor of mRNA (hnRNA) is transcribed by:
सही उत्तर: क) RNA polymerase II
RNA polymerase II transcribes hnRNA; polymerase I makes 28S, 18S and 5.8S rRNA, and polymerase III makes tRNA, 5S rRNA and snRNAs.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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DNA polymerase can synthesise a new DNA strand only in the:
सही उत्तर: घ) 5' to 3' direction
DNA polymerase adds nucleotides only to a free 3'-OH end, so new strands always grow 5' to 3'; this is why the lagging strand is discontinuous.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Which enzyme unwinds the DNA double helix at the replication fork?
सही उत्तर: घ) Helicase
Helicase breaks the hydrogen bonds between the base pairs and opens the two strands to form the replication fork.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The core of a nucleosome contains how many histone protein molecules?
सही उत्तर: ख) 8
A nucleosome core is a histone octamer (two each of H2A, H2B, H3 and H4) around which about 146 bp of DNA is wrapped.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In the B-form of DNA, the distance between two consecutive base pairs is:
सही उत्तर: ग) 0.34 nm
B-DNA has about 10 base pairs per turn with a pitch of 3.4 nm, so successive base pairs are 0.34 nm apart; the helix diameter is 2 nm.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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If the recombination frequency between two linked genes is 12%, the distance between them on the genetic map is:
सही उत्तर: क) 12 centimorgans
One map unit (centimorgan) equals 1% recombination, so 12% recombination corresponds to 12 cM.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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Phenylketonuria, an inborn error of metabolism, is caused by deficiency of the enzyme:
सही उत्तर: क) Phenylalanine hydroxylase
Lack of phenylalanine hydroxylase prevents conversion of phenylalanine to tyrosine, so phenylalanine and phenylpyruvic acid accumulate.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In birds, the heterogametic sex (producing two kinds of gametes) is:
सही उत्तर: ख) The female, with ZW chromosomes
Birds follow the ZW-ZZ system: females are ZW and produce two kinds of eggs, while males are ZZ.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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In grasshoppers, males have only one sex chromosome (one X and no Y). This type of sex determination is:
सही उत्तर: क) XX-XO type
In the XX-XO system females are XX and males are XO, so males have one chromosome fewer than females.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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The chromosome complement of a person with Klinefelter's syndrome is:
सही उत्तर: घ) 44 + XXY
Klinefelter's syndrome results from an extra X chromosome in a male, giving 47 chromosomes (44 + XXY); such males are sterile.
💬 टिप्पणी / गल्ती रिपोर्ट (०)
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