Question

Q3: The diagram below shows the results from the famous Meselson-Stahl experiment proving the semiconservative nature of DNA replication.  Note: after one generation (b) all the DNA was hybrid, after two generations (c), 50% of DNA is hybrid and 50% is light.

What would you expect to obtain if the bacteria were allowed to continue to divide:             (4 pts)

Results expected after 3^rd Generation: Percent Light DNA = __%,    Percent hybrid DNA __%

Results expected after 4^th Generation: Percent Light DNA = __%,    Percent hybrid DNA __%

Explain your results here:

Answer 1

* Meselson stahl experiment done by Matthew meselson and Franklin stahl in 1958 . They tested the hypothesis of DNA replication . Nitrogen is found in nitrogenous bases of each nucleotides so they decided to use an isotope of nitrogen to distinguish between parent and newly copied DNA .

•••••after third generation light DNA is 75% and hybrid DNA is 25% .

•••••after fourth generation light is 88 % and hybrid is 12% .

* DNA is made up of two strands based on the watson and crick model.

* if parent DNA has two strands , than each of the strand acts as a template and retains its integrity and forma a daughter strand .

* each of the parent DNA strand is shared by two daughter DNA .