Interphase in the cell cycle encompasses the G₁, S, and G₂ phases, as it shows the period of growth and DNA replication that a cell must go through to prepare for mitosis. Cell division, which occurs during the M phase, is the only portion of the cell cycle that is not included in interphase.

Because they do not divide, central nervous system nerve cells do not need to experience growth (G₁ and G₂ phases), DNA replication (S phase), or mitosis (M phase). As a result, they spend most of their lives arrested in G₀, a resting phase.

Cancer can often be the result of a problem with the checkpoint at the end of the G₂ phase, as this is the last stop for regulation before the cell undergoes division.

If this checkpoint is not functioning effectively, cells can undergo rapid and unregulated division, resulting in cancer. p53, a cancer suppressor gene, plays a key role in this checkpoint, and is commonly found to be mutated in cancer patients.

The S phase is when the cell replicates its DNA, resulting in chromatid pairs that will split apart during mitosis. The G phases are mainly dedicated to protein synthesis and cell growth. The M phase is the act of mitosis.

The G1 phase of the cell cycle serves the important function of giving the cell time to grow and replicate organelles. Formation of the mitotic spindle does not occur until prophase of mitosis, and DNA synthesis takes place during the S phase of the cell cycle. The G1 phase ensures that both daughter cells have adequate cellular machinery and organelles to survive after mitosis.

The key to this question is to remember the difference between chromosomes and sister chromatids. During the G2 phase the cell has already undergone DNA replication (in the S phase). Each of the chromosomes will therefore have identical sister chromatids. There will be 92 sister chromatids, but only 46 chromosomes. A chromosome is one entity that consists of the two sister chromatids bound together at the centromere.

During the G1 phase, DNA has not yet been replicated and there is only one copy of genetic information. The cell, however, is still diploid and contains information for 46 chromosomes, but only 46 chromatids. The S phase accounts for the duplication of chromatids, but does not change the total number of chromosomes.

A cell cycle has three crucial checkpoints. The checkpoints function to verify cellular processes and materials that are required for subsequent steps in the cell cycle.

The first checkpoint occurs between the G1 and S phase. The purpose of this checkpoint is to check if the cell is ready for DNA replication. The second checkpoint occurs between the G2 phase and prophase of mitosis (beginning of the M phase). The purpose of this checkpoint is to ensure the completion of replication and the integrity of DNA. The third checkpoint occurs between metaphase and anaphase. This checks if the chromosomes are properly attached at the metaphase plate. All three checkpoints are essential and are irreversible.

For this question we must identify processes that immediately follow a checkpoint. Option I is not correct because it is not preceded by a checkpoint. Option II is correct because sister chromatid separation occurs during anaphase, and anaphase is preceded by the third checkpoint. Similarly, option III is also correct because DNA replication occurs during the S phase, which is preceded by the first checkpoint.

Remember that DNA is replicated during the S phase of the cell cycle. Immediately after mitosis, the cell contains a single chromatid for each chromosome, for a total of 46 chromatids. This period corresponds to the G1 phase, during which the cell produces proteins and grows.

The S phase follows the G1 phase and doubles the amount of DNA to 92 chromatids, composing 46 complete chromosomes with two chromatids each. The S phase is followed by the G2 phase, which is followed by the M phase (or mitosis). Through this remaining period, until the conclusion of mitosis, the cell contains 92 chromatids.

Only G1 phase precedes the S phase and has half the amount of DNA as the rest of the cell cycle; therefore, cells in the G1 phase have the least amount of DNA.

Histones are nuclear proteins that organize and compact DNA. Histones act as core proteins around which DNA molecules can wrap and form nucleosomes. Since histones are proteins, they are mostly made up of amino acids.

Recall that amino acids are the building blocks of proteins, nucleotides are the monomers of nucleic acids, and monosaccharides are the monomers of carbohydrates. Fatty acids are a common component in lipids.

The checkpoints in the cell cycle are necessary to make sure the cell is ready to divide. Certain checkpoints will check the size of the cell, the integrity of the DNA, and the proper attachment of spindle fibers. If a cell fails to use these checkpoints, it can continue to divide even when it is not ready.

This unregulated division is a hallmark of cancer, in which a cell continuously divides without the necessary checkpoints. Cancerous cells often display genetic defects due to bypassing checkpoints.