# If you took more of the same randomly generated 1000 bp fragments of binturong DNA (the same sample that you used in the equilibrium density gradient centrifugation experiment described in part a and the C0t curve described in part b of this question) and used them as a sample in agarose gel electrophoresis, how many bands would you expect to find in the gel when you turned off the current and stained the gel with ethidium bromide? Briefly explain why you would predict that number of bands.

Question

picture with 1 graph is for question 1a)

picture with 4 graphs is for question 1b)

1a) E. coli DNA and binturong DNA are both 50% G-C. If you randomly shear E. coli DNA into 1000 bp fragments and put it through density gradient equilibrium centrifugation, you will find that all the DNA bands at the same place in the gradient, and if you graph the distribution of DNA fragments in the gradient you will get a single peak (see below). If you perform the same experiment with binturong DNA, you will find that a small fraction of the DNA fragments band separately in the gradient (at a different density) and give rise to a small "satellite" peak on a graph of the distribution of DNA fragments in the gradient (see below). Why do these two DNA samples give different results, when they're both 50% G-C?

1b) If you denatured the random 1000 bp fragments of binturong DNA that you produced in question 1a by heating them to 95ºC, and then cooled them down to 60ºC and allowed them to reanneal, you would find that approximately 15% of the DNA fragments renatured very rapidly, another 20% of the DNA fragments renatured moderately rapidly, and the remaining DNA fragments renatured relatively slowly. Which of the graphs shown below is a C0t curve showing these results?

1c) What fraction of the binturong genomic DNA would be considered to be "highly repetitive" DNA, based on this data?

1d) If the binturong genome is 2.87 x 109 base pairs, and the "highly repetitive DNA" fraction is composed entirely of copies of sequence 5'ATGGTCC3' and its complement, how many copies of this sequence are present in the binturong genome?

1e) Briefly explain, in your own words, why the fraction of the binturong DNA fragments that reannealed relatively slowly took so much longer to renature than the other DNA fragments.

1f) If you took more of the same randomly generated 1000 bp fragments of binturong DNA (the same sample that you used in the equilibrium density gradient centrifugation experiment described in part a and the C0t curve described in part b of this question) and used them as a sample in agarose gel electrophoresis, how many bands would you expect to find in the gel when you turned off the current and stained the gel with ethidium bromide? Briefly explain why you would predict that number of bands.