The total number of hydrogen bonds of a DNA-double Helix strand whose one strand has the following sequence of bases is ________.
5' - G - G - C - A - A - A - T - C - G - G - C - T - A - 3'

The given strand runs from the 5′-end to the 3′-end as
$$5' - G - G - C - A - A - A - T - C - G - G - C - T - A - 3'$$

To count the hydrogen bonds we need two facts:
1. $$G$$ pairs with $$C$$ through $$3$$ hydrogen bonds.
2. $$A$$ pairs with $$T$$ through $$2$$ hydrogen bonds.

Step 1 Count each type of base in the given strand:

  • $$G$$ appears $$4$$ times (positions 1, 2, 9, 10).
  • $$C$$ appears $$3$$ times (positions 3, 8, 11).
  • $$A$$ appears $$4$$ times (positions 4, 5, 6, 13).
  • $$T$$ appears $$2$$ times (positions 7, 12).

Step 2 Find the number of base pairs of each kind:

  • Total $$G\text{-}C$$ pairs $$= 4 + 3 = 7$$.
  • Total $$A\text{-}T$$ pairs $$= 4 + 2 = 6$$.

Step 3 Multiply by the corresponding hydrogen bonds:

  • Hydrogen bonds from $$G\text{-}C$$ pairs $$= 7 \times 3 = 21$$.
  • Hydrogen bonds from $$A\text{-}T$$ pairs $$= 6 \times 2 = 12$$.

Step 4 Add the two contributions:
$$\text{Total hydrogen bonds} = 21 + 12 = 33$$

Hence, the DNA double helix formed with this strand will have $$33$$ hydrogen bonds.