AP Biology 4.5 Cell Cycle and Mitosis
Practise AP Biology 4.5 questions by connecting interphase and DNA replication with mitotic chromosome distribution, cytokinesis and cell growth.
- Syllabus
- Effective Fall 2025
- Course
- AP Biology
Exam points
- sequence G1, S and G2 through mitosis and cytokinesis in the cell cycle
- explain how spindle fibers, kinetochores and microtubules distribute sister chromatids
- connect mitosis and cytokinesis to growth, tissue repair and asexual reproduction
- interpret fusion, drug-treatment or cell-count data to infer cell-cycle phase and regulation
Covered syllabus points
4.5 Cell Cycle question 1
Crossing over in meiosis I is required for homologous chromosomes to properly align during metaphase and segregate during the first cell division.
Describe the function of S phase of interphase.
Some regions of a chromosome called hotspots display a higher frequency of crossing over than other regions do. Crossing over is suppressed in chromosomal regions near the centromeres. The centromere region of a duplicated chromosome includes a collection of proteins that form a structure called the kinetochore. Scientists hypothesized that one or more of these kinetochore proteins are responsible for suppressing crossing over around the centromere.
To investigate their hypothesis, scientists modified chromosome 8 in yeast such that, in each cell, one chromosome from the pair of homologous chromosome 8s contained the gene encoding red fluorescent protein (RFP), while the other chromosome from the pair contained the gene encoding green fluorescent protein (GFP). Cells expressing RFP emit (give off) red light, and cells expressing GFP emit green light. Models of the modified chromosome 8 both before and after crossing over are shown in Figure 1.
Figure 1. Models of modified chromosome 8 used in the experiment (A) before and (B) after crossing over occurs at the hotspot
4.5 Cell Cycle question 2
A student collected samples of cells from a woody plant during the spring and produced the drawings below. Sample 1 was collected from the woody stem of the plant. Sample 2 was collected from the root tip of the plant. Cells in different steps of mitosis are labeled with letters A, B, C, D, and E in Sample 2.
Figure 1. Drawings of samples of plant cells collected from two locations in a woody plant during the spring
Question (a)
(a)
Describe the role of mitosis in the growth of a plant.
[ 1 ]
Question (b)
(b)
Explain why there are more cells observed in mitosis in the root tip than in the woody stem.
[ 1 ]
Question (c)
(c)
Refine the model in the space provided for your response by using the letters from four of the cell labels of Sample 2 to represent the sequential steps of mitosis.
[ 1 ]
Question (d)
(d)
Explain how the arrangement of cellular components during the step of mitosis portrayed by cell D in Sample 2 facilitates the proper distribution of chromosomes to the two daughter cells.
PAGE FOR ANSWERING QUESTION 5
[ 1 ]
All question bank results loaded