In: Biology
A bacteria culture is grown for many generations in a medium in which the only available nitrogen is the heavy isotope (15N). The culture is then switched to a medium containing only 14N for TWO generation of growth; it is then recultured to a 15N-containing medium for ONE final generation of growth. The DNA from these bacteria is isolated and centrifuged to equilibrium in a CsCl density gradient.
(a) Determine the proportion of 15N15N, 15N14N, and 14N14N DNA if the replication is following the semiconservative mode. Show your work to gain maximum mark.
(b) Determine the proportion of 15N15N, 15N14N, and 14N14N DNA if the replication is following the conservative mode. Show your work to gain maximum mark.
Note: You may hand-sketch the drawing in a piece of blank paper, scan or take a photo of your drawing, and attached it in your Word document.
DNA replication - copying of DNA is called DNA replication.
The mode of dna replication is semiconservative in organism but the hypothetically may be conservative and dispersive .
semiconservative -If after replication in DNA one strand is conserve and one strand new formed in one DNA molecule then this is called semi conservative mode of replication.
conservative - while if after replication one dna have both strand new and one dna both stand parental it means both are conserve . this is called conservative mode of replication.
from the question the data given , the calculation for both mode of replication that is semiconservative and conservative given below-