1. Samples may have fragments of different lengths due to the use of different restriction enzymes that cut the DNA at different locations, resulting in fragments of varying sizes. Additionally, the DNA sequence itself can also affect the length of the fragments produced by the restriction enzymes.
2. Each cell in the human body contains the same DNA sequence, but different types of cells can have variations in their DNA due to factors such as mutations and epigenetic modifications. Mutations are changes in the DNA sequence that can occur spontaneously or due to exposure to environmental factors such as radiation or chemicals. Epigenetic modifications are changes in the way that DNA is packaged and expressed, which can be influenced by factors such as diet, stress, and aging. These variations can result in differences in the number and length of DNA fragments between different types of cells, even if they come from the same person. Therefore, it is not safe to assume that all samples from the same person will have the same number and length of fragments.
3. Yes, the samples digested with EcoRi and smal would have different patterns because EcoRi and smal are different restriction enzymes that recognize and cut different DNA sequences. Therefore, they would produce different fragment sizes and patterns after digestion.