Question

what would happen if the bases in DNA strands were connected by a bond other than a hydrogen bond?

Answer 1

I don't think that complimentary bases in DNA can be bonded by anything else other than hydrogen bonds. But if it did, my guess is that the entire DNA strand and its structures would be completely changed and it's function would completely alter.

Answer 2

The actual result would depend on what kind of bond actually replaced the H bonds.

Energetically speaking, hydrogen bonds are sort of a 'middle of the road' bond: they're nowhere near as strong as covalent bonds, but they're among the strongest of the so called "non-bonded interactions."

If a stronger bond - i.e., a covalent bond - replaced H bonds between the bases, it's likely that the enzymes which first separate and then transcribe (RNA Polymerase) or replicate (DNA Polymerase) would not be strong enough or able to separate the strands. Or, if they were similarly altered so they could, the process would require far more energy than cells have available. You'd see very slow, very limited transcription and replication and you'd also see a decrease in other activities which require energy.

If a weaker bond replaced the H bonds, then the DNA molecule would have the opposite problem: the strands would tend to dissociate more frequently. The DNA would probably loose its structure a lot more often.