Question

Meselson and stahl experiment if ecoli is allowed to grow for 80minutes what would be the proportin of light and hybrid dna

Answer 1

E coli bacteria divides in every 20 min so in 80 min it will be four generations. 
N15 isotope is present in the environment than shifted in N14 environment, so it will result in the presence of N15 and N14 strands in DNA. 
In the second generation, half will have the previous hybrid bacteria and half will have the light bacteria. 
In the third generation, hybrid generation will again cut half, this time 25% hybrid and 75% light
In fourth generation, 16 copies will be hybrid and 14 will be light 

Answer 2

Hybrid (12.5 %) and light band (87.5%)

Explanation:

The life span of an E.coli bacteria is about 20 minutes that is after 20 minutes daughter cells will be produced.

Therefore the bacterial colony grows by an expression of $2^{n}$ in which n represents the generation.

To calculate n= total time divided/ generation time is used

In the given question, n=80/20= 4 generations.

Now in generations

1. First generation= 1 hybrid band is formed

2. Second generation= 1 hybrid (50%) and 1 light band( 50%) is formed

3. Third generation- Hybrid(25%) and light band (75%)

4. Forth generation= Hybrid (12.5 %) and light band (87.5%)

To learn more:

1. Meselson and Sthal experiment: https://brainly.in/question/8911389