Question

A cell biologist measured the DNA content of a cell from a fruit fly larva at the G1 phase and determined that it contained 150 units of DNA. The DNA content of the same type of cell at the G2 phase was determined to be 300 units of DNA. Which of the following statements best explains these results?

Answer 1

The DNA content of the cell doubles from the G1 to the G2 phase due to DNA replication during the S phase of the cell cycle. This ensures each new cell receives the same genetic information upon division.

Step-by-step explanation:

The cell biologist's measurements of the DNA content of a cell from a fruit fly larva show an increase from 150 units in the G1 phase to 300 units in the G2 phase. This result can be explained by the events occurring during the cell cycle, specifically the synthesis phase or S phase, where DNA replication takes place. Consequently, the amount of DNA in the cell doubles by the time the cell has entered the G2 phase, preparing the cell for mitosis.

During the S phase, all of the DNA in the cell is replicated. Thus, if a cell starts with 150 units of DNA (representing the entire genome) in the G1 phase, it would end up with 300 units (as each part of the genome has been replicated) by the G2 phase. The DNA content measurement in G2 reflects the duplicated chromosomes, each composed of two sister chromatids joined at the centromere, ready for subsequent division.

This process ensures that when the cell divides, each new cell will receive the same genetic information as the original cell, a key aspect of eukaryotic cell division and genetic consistency across an organism.