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Multiple Choice
Based on the graph showing the incorporation of radioactive nucleotides during DNA replication, which conclusion is best supported?
A
DNA replication does not require nucleotide incorporation.
B
DNA replication is dispersive, with both strands containing interspersed segments of old and new DNA.
C
DNA replication is semi-conservative, with each new DNA molecule containing one original and one new strand.
D
DNA replication is conservative, producing one molecule with both original strands and one with both new strands.
Verified step by step guidance
1
Step 1: Understand the concept of DNA replication. DNA replication is the process by which a cell duplicates its DNA before cell division. There are three main models of DNA replication: conservative, semi-conservative, and dispersive. Each model describes how the original DNA strands are distributed in the newly formed DNA molecules.
Step 2: Review the semi-conservative model of DNA replication. In this model, each new DNA molecule consists of one original (parental) strand and one newly synthesized strand. This was demonstrated experimentally by Meselson and Stahl using isotopic labeling of DNA.
Step 3: Analyze the graph showing the incorporation of radioactive nucleotides during DNA replication. Radioactive nucleotides are incorporated into newly synthesized DNA strands, allowing scientists to track the synthesis of new DNA. If the graph shows equal incorporation into both strands of the new DNA molecules, it supports the semi-conservative model.
Step 4: Compare the semi-conservative model to the other models. The conservative model suggests that one DNA molecule retains both original strands, while the other contains two new strands. The dispersive model suggests that both DNA molecules contain interspersed segments of old and new DNA. The graph data should help distinguish between these models.
Step 5: Conclude that the semi-conservative model is best supported by the graph. The incorporation of radioactive nucleotides into one strand of each new DNA molecule aligns with the semi-conservative model, where each new DNA molecule contains one original strand and one new strand.