Microsatellite DNA, also known as short tandem repeats (STRs), are sequences of DNA that repeat themselves consecutively and are scattered throughout the genome. They have proven to be very useful in the field of genetics for various purposes.

Option 1 is correct. Scientists use microsatellite DNA sequences to study evolutionary relationships among different species of animals. Differences in these sequences can reveal evolutionary changes, as they mutate relatively quickly, allowing us to track patterns of inheritance and construct family trees of related species.

Option 2 is incorrect. Stem cell stimulation involves the transformation of these cells into various types of functional tissues, which is not directly related to microsatellite DNA.

Option 3 is also incorrect. Clonal propagation of plants, a practice used in horticulture, primarily involves asexual reproduction and does not widely use microsatellite DNA.

Option 4 is incorrect because, while DNA sequences can be involved in the trial and development of drugs, microsatellite DNA is not specifically used for assessing the effectiveness of different drugs in a population.