Passage
Trypanosoma brucei is a eukaryotic parasite that causes sleeping sickness in Sub-Saharan Africa. The cell cycle of T. brucei differs from that of higher eukaryotes. For example, the chromatin does not condense during mitosis, and the nuclear envelope remains intact. In addition, the nucleus divides before cell division, and the cell divides along the longitudinal axis (Figure 1) .
Figure 1 Mitosis in T. bruceiA culture of T. brucei was arrested in S phase of the cell cycle by overnight incubation with the reversible inhibitor hydroxyurea. The cells were then washed, and their progression through the cell cycle was monitored by flow cytometry and microscopy. A subset of the culture was first exposed to the drug VX-680, which arrests cells upon completion of metaphase. The results are shown in Figure 2.
Figure 2 Percentages of a population of T. brucei cells in each phase of the cell cycle, measured at different time points in the (A) absence and (B) presence of VX-680
Adapted from Li Z, Umeyama T, Wang CC. The Aurora Kinase in Trypanosoma brucei plays distinctive roles in metaphase-anaphase transition and cytokinetic initiation. PLoS Pathog. 2009;5(9) :e1000575.
-T. brucei cells and higher eukaryotes are similar in that they both undergo:InterphaseProphaseCytokinesis

Question

Passage
Trypanosoma brucei is a eukaryotic parasite that causes sleeping sickness in Sub-Saharan Africa. The cell cycle of T. brucei differs from that of higher eukaryotes. For example, the chromatin does not condense during mitosis, and the nuclear envelope remains intact. In addition, the nucleus divides before cell division, and the cell divides along the longitudinal axis (Figure 1) .

Figure 1 Mitosis in T. bruceiA culture of T. brucei was arrested in S phase of the cell cycle by overnight incubation with the reversible inhibitor hydroxyurea. The cells were then washed, and their progression through the cell cycle was monitored by flow cytometry and microscopy. A subset of the culture was first exposed to the drug VX-680, which arrests cells upon completion of metaphase. The results are shown in Figure 2.

Figure 2 Percentages of a population of T. brucei cells in each phase of the cell cycle, measured at different time points in the (A) absence and (B) presence of VX-680
Adapted from Li Z, Umeyama T, Wang CC. The Aurora Kinase in Trypanosoma brucei plays distinctive roles in metaphase-anaphase transition and cytokinetic initiation. PLoS Pathog. 2009;5(9) :e1000575.
-T. brucei cells and higher eukaryotes are similar in that they both undergo:InterphaseProphaseCytokinesis

Quizplus · Accepted Answer

11ecba2d_101a_33e3_a3bf_ff2425e975db_MD0008_00 The cell cycle is broadly divided into two phases: interphase and the mitotic (M) phase. Interphase consists of two gap phases (G₁ and G₂) that are separated by a synthesis (S) phase. During G₁, cells grow, produce organelles, and assemble molecular machinery. In the S phase that follows, DNA is replicated. Cells then enter G₂, during which cells continue to grow. M phase consists of mitosis and cytokinesis. During mitosis (which consists of prophase, metaphase, anaphase, and telophase) identical sets of chromosomes are segregated into two nuclei. Afterward, the cell membrane divides to allow the formation of two daughter cells (ie, cytokinesis). The passage states that T. brucei cells were arrested in S phase. Because S phase is a part of interphase, T. brucei cells undergo interphase (Number I). In addition, Figure 2A shows that all three stages of interphase (G₁, S, and G₂) occur in T. brucei. Figure 1 shows that in M phase, T. brucei cells undergo cytokinesis longitudinally, along the longest axis (Number III). (Number II) During prophase, the first phase of mitosis in many eukaryotes, chromatin condenses into distinct chromosomes, and the nuclear envelope disintegrates. However, according to the passage, the chromatin in T. brucei cells does not condense, and the nuclear envelope remains intact throughout mitosis. Therefore, unlike higher eukaryotes, T. brucei do not undergo prophase. Educational objective: The cell cycle consists of interphase (G₁, S, and G₂) and the mitotic (M) phase. In M phase, chromosomes are segregated into two nuclei. During the first phase of M phase (ie, prophase), chromatin condenses into chromosomes and the nuclear envelope disintegrates, allowing the cell to progress into the remaining phases of M phase (ie, metaphase, anaphase, and telophase). Cytokinesis, or the division of the cell membrane, then yields two daughter cells.

Passage Trypanosoma Brucei Is a Eukaryotic Parasite That Causes Sleeping Sickness