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?

Question

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? (A) All four still contain radioactivity (B) Three out four contain radioactivity (C) Radioactivity is lost from all four (D) Half the number contain no radioactivity

Tardigrade Admin · Accepted Answer

DNA replication is semiconservative, i.e., during each replication cycle, 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. <img class="img-fluid question-image" alt="Solution" src="https://cdn.tardigrade.in/q/nta/b-iqxm1sqjn2i0.png" />

Q. 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?

All four still contain radioactivity

Three out four contain radioactivity

Radioactivity is lost from all four

Half the number contain no radioactivity

DNA replication is semiconservative, i.e., during each replication cycle, 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.