AP BIOLOGY

Detailed explanation-1: -A checkpoint is a stage in the eukaryotic cell cycle at which the cell examines internal and external cues and “decides” whether or not to move forward with division.

Detailed explanation-2: -In eukaryotes, the cell cycle consists of four discrete phases: G1, S, G2, and M. The S or synthesis phase is when DNA replication occurs, and the M or mitosis phase is when the cell actually divides.

Detailed explanation-3: -At the molecular level, however, interphase is the time during which both cell growth and DNA replication occur in an orderly manner in preparation for cell division.

Detailed explanation-4: -During metaphase, all of the chromosomes are aligned in a plane called the metaphase plate, or the equatorial plane, midway between the two poles of the cell. The sister chromatids are still tightly attached to each other. At this time, the chromosomes are maximally condensed.

Detailed explanation-5: -During prophase, the “first phase, ” the nuclear envelope starts to dissociate into small vesicles, and the membranous organelles (such as the Golgi apparatus and endoplasmic reticulum), fragment and disperse toward the edges of the cell. The nucleolus disappears.