Question

If E.coli was allowed to grow for 80 minutes then what would be the proportions of light and hybrid densities DNA molecules?

Answer 1

E. coli is a harmless bacteria which lives in our intestines. But some specific strains can be harmful. They are gram-negative, rod-shaped bacteria. They can cause pneumonia. Every strain takes a particular time to replicate.

Complete answer:
Like other pathogens, E.coli can also be harmful sometimes when present in excess growth. In the gut, it can replicate and attack our immune system or a target to infect us.
In a DNA molecule, there are two strands which replicate in a semi-conservative manner. The two strands are the heavy and light chains. The light chain is produced to every template heavy chain. So an organism has the hybrid of these chains.
Hybrid has the heavy-light double helix strand.
E. coli takes 20 minutes to divide. So after 80 minutes, there will be four generations.
At time = 0, there are no light and hybrid strands, there is only 1 heavy strand.
After 20 minutes, the first generation will be formed. It will have all the hybrid strands. Which means all the new DNA will be intermediate.
After 40 minutes, we will have a second generation. In this half of the DNA will be hybrid strand and the other half will be light strand.
After 60 minutes, we will have a third-generation having 25% hybrid and 75% light strands.
After 80 minutes, we will have the fourth generation which will have 12.5% hybrid strand and 87.5% light strand.

Note:
The concept used in the question is from Meselson Stahl's Semi conservative nature of DNA replication. This states that each strand of DNA serves as a template to produce a new strand which will be complementary to the template strand. It was observed and tested on the E.coli.