17 hydrogen bonds exist between the given DNA strand and its complementary DNA strand.

Explanation:

Given DNA strand is 5′-CATAGGA-3′
The complementary of this is 3′-GTATCCT-5′

We know that the Pair of A-T have two hydrogen bonds and
Pair of C-G has three hydrogen bonds.

So, in the given strand and its complementary, there are 3 C-G pairs and 4 A-T pairs.

So, the total number of hydrogen bonds = 3 * (Hydrogen bonds in C-G pair) + 2 * (Hydrogen bonds in A-T pair)

=> 3 * 3 + 4 * 2

=> 9 + 8 = 17 hydrogen bonds.