Advanced Placement (AP) Biology Practice Exam

What does cleavage refer to in cell biology?

1. The process during animal cell cytokinesis

2. A form of apoptosis

3. The sequence of DNA replication

4. The formation of a zygote

The correct answer is: The process during animal cell cytokinesis

Cleavage in cell biology specifically refers to the series of rapid cell divisions that follow fertilization, which result in the segmentation of the fertilized egg. This process is particularly prominent in animal development, where after the zygote is formed, it undergoes cleavage to produce a multicellular structure known as the blastula. During animal cell cytokinesis, which is when the cytoplasm of a parental cell is divided into two daughter cells, the term "cleavage" is applied. This refers to the manner in which the cytoplasm is split, often resembling a cleaving or cutting action, particularly in the use of terms such as "cleavage furrow" that denotes the indentation forming during this process. The other options, while related to biological processes, do not define cleavage. The formation of a zygote indeed occurs following fertilization but refers to the initial single cell stage rather than the division processes that follow. A form of apoptosis relates to programmed cell death, which is distinct from the division processes described in cleavage. DNA replication refers to the process of duplicating the DNA, which is separate from the processes involved in cleavage and division. Overall, the correct answer clearly illustrates the specific context of cell division in early embryonic development, capturing