Noam123

Another reason for double stranded DNA is because in this way each strand has a backup strand, so if one strand is damaged, the other holds the information to correct it. Try to run your Hard Drive without a backup and we'll see how far you'll reach...

I read these two things in the book "Molecular Biology of THE CELL" (fourth edition): 1. (Page 540) "In mammals, for example, linear DNA fragments introduced into cells are rapidly ligated end-to-end by intracellular enzymes to form long tandem arrays, which usually become integrated into a chromosome at an apparently random site". 2. (Page 541) "If a DNA molecule carrying a mutated mouse gene is transferred into a mouse cell, it usually inserts into the chromosomes at random, but about once in a thousand times, it replaces one of the two copies of the normal gene by homologous recombination". Now, I would like to know if what said in #2, that the DNA molecule introduced into mice cells will usually insert at random (and only rarely in HR), will only happen if, like said in #1, this DNA molecule is linear. Does this mean that if I introduce a mice cell with a mutated gene on a Plasmid DNA (not linear, rather circular), then the chances for random integration are drastically lower than the chances of Homologous Recombination ? (pay attention, I'm not asking if the chances of HR will be higher in total, I'm just asking if in this case they will be higher than the chances of random integration). Do you understand my question ?, can you answer it or please direct me to somewhere I can find the answer ?. Thank you very much for your help and time.