In the meselson-stahl experiment, cells were grown for one generation in growth medium containing a relatively heavy nitrogen isotope, then transferred to new medium containing a lighter nitrogen isotope. after one round of dna replication, what was true of the dna in the cells?

Out of the following give choices;

a. All DNA strands contained only the heavy nitrogen isotope.

b. Half of the DNA strands contained only the light nitrogen isotope.

c. All DNA strands contained both heavy and light nitrogen isotopes.

d. All DNA strands contained only the lighter nitrogen isotope.

The answer is b. Meselson–Stahl experiment demonstrated the semi-conservative model of DNA replication. When DNA is replicated, one strand of the new double helix strand is the parent's strand while the other is the newly synthesized one. This made the semiconservative model stand out over the other two, dispersive and conservative models.

it has to be understood that the sea water contains a huge amount of sodium and chlorine ions and if they enter the cell of the atlantic cod fish, the cell will shrivel and the fish will die. to avoid such a condition, the fish uses active transport for the purpose of removing the ions against the gradient.

explanation:

the atlantic cod is not a maritime osmoconformer. its native application of salts is less than that of the seawater it lives in. it is continually falling water from the gills to the ocean via osmosis.

countering that, the fish is going to be swallowing seawater. but since its internal collection of salts is lower than seawater, the fish will want to go free of excess salt, and since that's going upon a gradient, then active transport, requiring energy, must be used to pump out the salt. much marine fish use the organs to filter out the salt and these fish discharge very straight urine.