When examining cells in the laboratory, you notice that a particular cell has half as much DNA as the surrounding cells. It appears that this cell's cell cycle halted at checkpoint .

G1 checkpoint

Explanation:

The cell cycle consists of the series of activities that occurs from the replication of DNA to the actual division of the cell in an organism's cell. However, the cell has been internally programmed to ensure that all conditions are in place/favorable before allowing progression into the next stage of the cell cycle. This internally controlled mechanism ia called CHECKPOINTS. This checkpoint occurs at three main stages of the cell cycle;

after G1 phase, G2 phase and during M phase.

In the G1 checkpoint, the cell ensures that the cell is in the right shape to proceed into the Synthesis phase of the cell cycle where it will double it's DNA. The checkpoint checks majorly for damage or change to the DNA before replicating it. If any error is found, that cell is halted and prevented from proceeding to the S-phase of the cell cycle.

This is the case in the question, the cell has been halted and prevented from entering the S-phase. Hence, its DNA is still the same as it started. However, the DNA of the cells surrounding it has been doubled as they have undergone DNA replication during S-phase.

white blood cells or wbc s are mainly 2 types-

1.agranulocytes

2.granulocytes

the monocytes or macrophages of agranulocytes , dendritic cells which are accessory leucocytes, and b cells which is one type of lymphocytes   identify the antigens present on the pathogen's surface. these three cells are called antigen presenting cells(apc) which are phagocytes and destroy the antigens by secreting antitoxins. besides this leukocyte is always plays vital role in the immunity of the body.

the second type of galaxy is called a barred spiral, which has a thing called a bar straddling the nucleus