In the Meselson-Stahl experiment, 15N-labeled cells were shifted to 14N medium a
ID: 168996 • Letter: I
Question
In the Meselson-Stahl experiment, 15N-labeled cells were shifted to 14N medium at what is designated as generation 0. For the semiconservative model of replication, what proportion of 15N-15N, 15N- 14N, and 14N-14N would you expect to find after one replication cycle?
15N-15N
15N-14N
14N-14N
75%
50%
87.5%
0%
12.5%
100%
G.
25%
expect to find after three replication cycles?
15N-15N
15N-14N
14N-14N
A.
25%
100%
75%
0%
12.5
50%
87.5%
A.75%
B.50%
C.87.5%
D.0%
E.12.5%
F.100%
G.
25%
expect to find after three replication cycles?
15N-15N
15N-14N
14N-14N
A.
25%
B.100%
C.75%
D.0%
E.12.5
F.50%
G.87.5%
Explanation / Answer
In first case the DNA obtained will contain the intermediate dna fragments, N-14 & N-15..Hence the % after first generation will be
N-15 & N-15 - 0%..
N-15 & N-14- 100%..
N-14 & N-14 - 0%..
As the both the strands of the DNA opens as one of the parental strand remains same in the new strand hence the medium 14 strands will be synthesized every time other strand comes from the parents.!!
After 3 cycles it will be.. :-
As the DNA follows the semiconservative methods soo
N14-N-14 will be 75%..
N15 & N14 - 25%..
N15 & N15 will be 0%..