Molecular Basis of Inheritance Question 96
96. If a completely radioactive double stranded DNA molecule undergoes two rounds of replication in a non-radioactive medium, what will be the radioactive status of the four resulting molecules?
[1997]
(a) Half the number contain no radioactivity
(b) All four still contain radioactivity
(c) Three out of four contain radioactivity
(d) Radioactivity is lost from all four
Show Answer
Answer : a
Hints & Solution
(a) DNA replication is semiconservative. i.e. at each replication one of the parental strands is retained and a new daughter strand is obtained. Thus only half of the parental DNA molecule is carried to the next generation. $\longrightarrow{$ radioactive DNA
