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Biomolecules question

2025 · 4 Apr · Shift 1 · Q25
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Biomolecules question

2025 · 4 Apr · Shift 1 · Q25

JEE MainChemistryBiomoleculesNumerical+4 / −1
The total number of hydrogen bonds of a DNA-double Helix strand whose one strand has the following sequence of bases is ‾\underline{\hspace{2cm}}​. 5′−G−G−C−A−A−A−T−C−G−G−C−T−A−3′5^{\prime}-\mathrm{G}-\mathrm{G}-\mathrm{C}-\mathrm{A}-\mathrm{A}-\mathrm{A}-\mathrm{T}-\mathrm{C}-\mathrm{G}-\mathrm{G}-\mathrm{C}-\mathrm{T}-\mathrm{A}-3^{\prime}5′−G−G−C−A−A−A−T−C−G−G−C−T−A−3′
Numerical answer
View written solutionFree

Correct answer: 33

  1. In DNA, the base pairing rules are:

    • A\mathrm{A}A pairs with T\mathrm{T}T by 2 hydrogen bonds.
    • G\mathrm{G}G pairs with C\mathrm{C}C by 3 hydrogen bonds.
  2. Given one strand: 5′−G−G−C−A−A−A−T−C−G−G−C−T−A−3′5'-\mathrm{G}-\mathrm{G}-\mathrm{C}-\mathrm{A}-\mathrm{A}-\mathrm{A}-\mathrm{T}-\mathrm{C}-\mathrm{G}-\mathrm{G}-\mathrm{C}-\mathrm{T}-\mathrm{A}-3'5′−G−G−C−A−A−A−T−C−G−G−C−T−A−3′

  3. Count the number of each type of base in the given strand:

    • G\mathrm{G}G appears at positions 1,2,9,101,2,9,101,2,9,10 ⇒4\Rightarrow 4⇒4
    • C\mathrm{C}C appears at positions 3,8,113,8,113,8,11 ⇒3\Rightarrow 3⇒3
    • \mathrm[A} appears at positions 4,5,6,134,5,6,134,5,6,13 ⇒4\Rightarrow 4⇒4
    • T\mathrm{T}T appears at positions 7,127,127,12 ⇒2\Rightarrow 2⇒2
  4. Total number of G\mathrm{G}G and C\mathrm{C}C bases: 4+3=74+3=74+3=7 Each G−C\mathrm{G-C}G−C pair contributes 333 hydrogen bonds. So hydrogen bonds from these pairs: 7×3=217 \times 3 = 217×3=21

  5. Total number of A\mathrm{A}A and T\mathrm{T}T bases: 4+2=64+2=64+2=6 Each A−T\mathrm{A-T}A−T pair contributes 222 hydrogen bonds. So hydrogen bonds from these pairs: 6×2=126 \times 2 = 126×2=12

  6. Hence, total hydrogen bonds in the DNA double helix are: 21+12=3321 + 12 = 3321+12=33

Therefore, the required integer answer is 333333.

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