The embryo that developed was implanted into a surrogate mother sheep, and was born as Dolly, with the exact DNA from the original udder cell. Creating livestock to serve as organ donors, or blood donors. Heat a starting quantity of DNA to separate the double helix. Add a collection of all four nucleotides, and DNA polymerase to copy the DNA, and some primers, and cool the sample. Primers are short sections of DNA that are complementary to the region on both ends of the DNA that you wish to copy.
Primers act as signals to tell DNA polymerase where to copy.
As the solution cools, they stick to the DNA you wish to copy and allow polymerase to do its job. So many bases, it is best to visualize them all in some organized fashion. Restriction enzymes can be used to cleave the chromosomes from many cells into manageable pieces. There will be a collection of copies of fragment 1, which is a different size than fragment 2, and so on. Dyes that bind DNA can then be used to visualize the fragments as bands that can be compared to reference DNA fragments of known size.