E. coli DNA and hippopotamus DNA are both 50% G-C. If you randomly shear E. coli
ID: 52136 • Letter: E
Question
E. coli DNA and hippopotamus 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. If you perform the same experiment with hippopotamus 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 two small "satellite" peaks on a graph of the distribution of DNA fragments in the gradient. Why do these two DNA samples give different results, when they're both 50% G-C?
Explanation / Answer
Hippopotamus DNA isHighly repetitive DNA and often termed as Satellite DNA which can be isolated as separate band in buoyant density centrifugation. They are highly repetitive, where the repeat length varies for one few bp to hundred bps or more. If some sequences consisting of two to many 200 bp long and they are repeated tandemly, means one after another many times.
E. coli DNA is non repetitive
Due to the presence of centromere, short arm of the chromosome may give rist to small "satellite" peaks.
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