Question

Mobile genetic elements continue to exist despite the fact that their actual activity would seem to disrupt the fidelity of the hereditary material. This is because:

1) Their mechanisms are too advanced for the cell's defenses to control
2) Their activity is so infrequent that there is no real effect on the DNA
3) The occasional DNA rearrangement and additions are beneficial over the long term
4) Their continued existence is, in fact, still a scientific mystery that does not seem to make sense

Answer 1

Option 4.

The rate of DNA renaturation is influenced by factors like temperature, DNA concentration, and length of DNA strands, but not by the presence of divalent cations, which stabilize DNA structure rather than influencing renaturation kinetics.

Step-by-step explanation:

The rate of DNA renaturation is influenced by various factors, which determine how quickly separated DNA strands can re-anneal to again form a double helix. These factors include:

1. Temperature: The rate of renaturation generally increases as temperature is raised, but only up to a point before high temperatures start causing denaturation.
2. Concentration of DNA: The probability of strands finding their complementary matches is higher when there's a greater concentration of DNA.
3. Length of DNA strands: Longer DNA strands may take longer to renature due to the increased complexity of aligning and binding.

However, the presence of divalent cations such as Mg2+ and Ca2+ does not influence the rate of DNA renaturation significantly.

These cations are more involved in stabilizing the structure of DNA, particularly during processes such as DNA replication and enzymatic reactions, but they don't play a major role in the renaturation kinetics.

The correct option in the context of the factors not influencing the rate of DNA renaturation is therefore the presence of divalent cations.