Which of the following events does not take place in prophase? Possible Answers: Sister chromatids are separated. Centrioles move to the opposite ends of the cell. Correct answer: Sister chromatids are separated. Explanation : Prophase is the first stage of mitosis, during which the cell begins to position itself in order to separate the chromatids and divide.
Chromatid separation is not seen until anaphase. Possible Answers: Prophase, metaphase, anaphase, telophase, cytokinesis. Prophase, interphase, metaphase, anaphase, telophase. Anaphase, prophase, metaphase, telophase, interphase.
Anaphase, cytokinesis, metaphase, prophase, telophase. Correct answer: Prophase, metaphase, anaphase, telophase, cytokinesis. Explanation : There are five main steps of mitosis. Prophase: the nuclear envelope breaks down, chromosomes condense, and spindle fibers connect to sister chromatids.
Metaphase: spindle fibers pull sister chromatids to the metaphase plate at the equator of the cell. Anaphase: spindle fibers separate sister chromatids to opposite poles of the cell. Cytokinesis: the cell cytoplasm splits completely in half where the cleavage formed, giving two identical daughter cells with the same chromosomes as the parent. In which phase of mitosis do chromosomes align at the center and spindle fibers become visible?
Possible Answers: Interphase. Correct answer: Metaphase. Explanation : Mitosis involves four distinct stages: prophase, metaphase, anaphase, and telophase.
What is the correct sequence of the stages of the M phase of the cell cycle? Possible Answers: Telophase, anaphase, metaphase, prophase. Explanation : The mitosis M phase of the cell cycle has four sequential stages: prophase, metaphase, anaphase, and telophase. The division of centromeres occurs during which phase of mitosis? Possible Answers: Telophase. Explanation : Centromeres are the structures at the center of each chromosome that hold the sister chomatids together.
Which of the following events is characteristic of telophase in mitosis? Possible Answers: Formation of spindle fibers. Correct answer: Uncoiling of chromosomes. Explanation : Mitosis has four sequential stages: prophase, metaphase, anaphase, and telophase.
Correct answer: G1. Explanation : The G1 phase is the first phase within interphase. Possible Answers: S phase. Correct answer: G0. Explanation : G0 phase is a post-mitotic phase. Copyright Notice.
View Tutors. Cristina Certified Tutor. Jordan Certified Tutor. University of Alabama at Birmingham, Bachelor of Sc Matilda Certified Tutor. London Metropolitan University, Bachelors, Biochemistry. University of the Western Cape, Masters, Biotechnology. Nature Reviews Molecular Cell Biology 2, 72 All rights reserved. Prophase is the first stage in mitosis, occurring after the conclusion of the G 2 portion of interphase.
During prophase, the parent cell chromosomes — which were duplicated during S phase — condense and become thousands of times more compact than they were during interphase.
Because each duplicated chromosome consists of two identical sister chromatids joined at a point called the centromere , these structures now appear as X-shaped bodies when viewed under a microscope. Several DNA binding proteins catalyze the condensation process, including cohesin and condensin.
Cohesin forms rings that hold the sister chromatids together, whereas condensin forms rings that coil the chromosomes into highly compact forms. The mitotic spindle also begins to develop during prophase. As the cell's two centrosomes move toward opposite poles, microtubules gradually assemble between them, forming the network that will later pull the duplicated chromosomes apart. When prophase is complete, the cell enters prometaphase — the second stage of mitosis.
During prometaphase, phosphorylation of nuclear lamins by M-CDK causes the nuclear membrane to break down into numerous small vesicles. As a result, the spindle microtubules now have direct access to the genetic material of the cell. As prometaphase ends and metaphase begins, the chromosomes align along the cell equator. Every chromosome has at least two microtubules extending from its kinetochore — with at least one microtubule connected to each pole.
At this point, the tension within the cell becomes balanced, and the chromosomes no longer move back and forth. In addition, the spindle is now complete, and three groups of spindle microtubules are apparent.
Kinetochore microtubules attach the chromosomes to the spindle pole; interpolar microtubules extend from the spindle pole across the equator, almost to the opposite spindle pole; and astral microtubules extend from the spindle pole to the cell membrane.
Metaphase leads to anaphase , during which each chromosome's sister chromatids separate and move to opposite poles of the cell. Enzymatic breakdown of cohesin — which linked the sister chromatids together during prophase — causes this separation to occur. Upon separation, every chromatid becomes an independent chromosome.
Meanwhile, changes in microtubule length provide the mechanism for chromosome movement. More specifically, in the first part of anaphase — sometimes called anaphase A — the kinetochore microtubules shorten and draw the chromosomes toward the spindle poles. Then, in the second part of anaphase — sometimes called anaphase B — the astral microtubules that are anchored to the cell membrane pull the poles further apart and the interpolar microtubules slide past each other, exerting additional pull on the chromosomes Figure 2.
Figure 2: Types of microtubules involved in mitosis During mitosis, several types of microtubules are active. The motor proteins associated with the interpolar microtubules drive the assembly of the spindle. Note the other types of microtubules involved in anchoring the spindle pole and pulling apart the sister chromatids.
Figure Detail. Cytokinesis is the physical process that finally splits the parent cell into two identical daughter cells. During cytokinesis, the cell membrane pinches in at the cell equator, forming a cleft called the cleavage furrow. The position of the furrow depends on the position of the astral and interpolar microtubules during anaphase.
The cleavage furrow forms because of the action of a contractile ring of overlapping actin and myosin filaments. As the actin and myosin filaments move past each other, the contractile ring becomes smaller, akin to pulling a drawstring at the top of a purse.
When the ring reaches its smallest point, the cleavage furrow completely bisects the cell at its center, resulting in two separate daughter cells of equal size Figure 3. Atom RSS Feed Chromosome condensation Definition Chromosome condensation is the dramatic reorganisation of the long thin chromatin strands into compact short chromosomes that occurs in mitosis and meiosis. Nature Cell Biology 23 , Research 17 June Nuclear dihydroxyacetone phosphate signals nutrient sufficiency and cell cycle phase to global histone acetylation Zhang et al.
Nature Metabolism 3 , Research 17 August Open Access Identifying proteins bound to native mitotic ESC chromosomes reveals chromatin repressors are important for compaction Epigenetic information is transmitted from mother to daughter cells through mitosis. Nature Communications 11 , Research 30 July Open Access Post-replicative pairing of sister ter regions in Escherichia coli involves multiple activities of MatP Protein, MatP, binds to and delays segregation of the ter region of the bacterial chromosome before cell division.
Research 03 October FACT mediates cohesin function on chromatin The histone chaperone FACT interacts directly with cohesin and contributes to the functions of cohesin in nuclear organization during interphase and during mitotic chromosome folding in S. Nature Cell Biology 21 , Research Highlights 20 February A stairway to mitotic chromosome assembly Condensin complexes drive mitotic chromosome formation by structuring chromatin into nested loops and organizing them along a central, helical scaffold.
Nature Reviews Molecular Cell Biology 19 , Research Highlights 23 August Different turfs for cohesin and condensin In yeast, mitotic chromosome condensation is achieved by cis -chromatin looping, a process in which cohesin and condensin have distinct roles. Nature Reviews Molecular Cell Biology 18 , Research Highlights 28 June Structuring interphase chromatin The oligomerization of scaffold attachment factor A through its binding to chromatin-associated RNAs regulates the structure of interphase chromosomes.
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