What Are The Different Stages Of The Cell Cycle – The cell cycle is a sequence of events involving cell growth and cell division that produces two new daughter cells. Cells on their way to cell division proceed through precisely timed and carefully timed phases of growth, DNA replication and division that produce two genetically identical cells. The cell cycle has two main phases: interphase and mitotic phase (Figure 6.3). During interphase, cells grow and DNA is replicated. During the mitotic phase, the replicated DNA and cytoplasmic contents are separated and the cell divides.
Figure 6.3 Cells move through phases in an orderly manner. During interphase, G1 involves cell growth and protein synthesis, S phase involves DNA replication and centrosome replication, and G2 involves growth and protein synthesis. The mitotic phase follows the interphase. Mitosis is nuclear division during which duplicated chromosomes are separated and distributed into daughter nuclei. Cells usually divide after mitosis in a process called cytokinesis in which the cytoplasm is divided and two daughter cells are formed.
- 1 What Are The Different Stages Of The Cell Cycle
- 1.1 Cell Cycle Stages
- 1.2 Anatomy, Physiology And Hygiene . Fig. 3.cell Division —various Stages.. Similar To Themselves, Mainly By What Is Known As Celldivision, — I.e. Each Cell Divides Into Two, Which Are Likethe Parent Cell,
- 1.3 Solution: Cell Cycle Stages Images And Description
- 1.4 Make Like A Cell And Split: Comparing Mitosis And Meiosis
What Are The Different Stages Of The Cell Cycle
During interphase, cells go through normal processes while still preparing for cell division. For a cell to move from interphase to mitotic phase, several internal and external conditions must be met. The three stages of interphase are called G
Cell Cycle Stages
Stage, cells are quite active at the biochemical level. Cells are accumulating the building blocks of DNA chromosomes and related proteins, as well as accumulating enough energy reserves to complete the task of replicating each chromosome in the nucleus.
Throughout interphase, nuclear DNA remains in a semi-condensed chromatin configuration. During the S phase (synthetic phase), DNA replication results in the formation of two identical copies of each chromosome – sister chromatids – which are tightly attached to the centromere region. At this stage, each chromosome is made from two sister chromosomes and is a duplicate chromosome. The centrosome is duplicated during the S phase. The two centrosomes give rise to the mitotic spindle, a device that orchestrates the movement of chromosomes during mitosis. The centrosome consists of a pair of rod-like centrioles at right angles to each other. Centrioles help organize cells. Centrioles are absent in the centrosomes of many eukaryotic species, such as most plants and fungi.
Phase, or the second gap, the cell replenishes its energy stores and synthesizes proteins necessary for chromosome manipulation. Some cell organelles are duplicated, and the cytoskeleton is dismantled to provide resources for the mitotic spindle. There may be additional cell growth during G
. The final preparations for the mitotic phase must be completed before the cell can enter the first stage of mitosis.
Anatomy, Physiology And Hygiene . Fig. 3.cell Division —various Stages.. Similar To Themselves, Mainly By What Is Known As Celldivision, — I.e. Each Cell Divides Into Two, Which Are Likethe Parent Cell,
To make two daughter cells, the contents of the nucleus and cytoplasm must be divided. The mitotic phase is a multistep process during which duplicated chromosomes are aligned, separated, and moved to opposite poles of the cell, and then the cell is divided into two identical daughter cells. The first part of the mitotic phase, mitosis, consists of five steps, which complete nuclear division. The second part of the mitotic phase, called cytokinesis, is the separation of cytoplasmic components into two daughter cells.
Mitosis is divided into phases – prophase, prometaphase, metaphase, anaphase, and telophase – which result in the division of the cell’s nucleus (Figure 6.4).
Figure 6.4 Animal cell mitosis divides into five phases – prophase, prometaphase, metaphase, anaphase, and telophase – seen under a fluorescence microscope. Mitosis is often accompanied by cytokinesis, shown here by transmission electron microscopy. (“diagram” credit: modified work by Mariana Ruiz Villareal; “mitosis micrograph” credit: modified work by Roy van Heesbeen; “cytokinesis micrograph” credit: modified work by Wadsworth Center, New York State Department of Health; donated to Wikipedia Foundation; scale bar information by Matt Russell)
During prophase, the “first stage,” several events must occur to allow the chromosomes to enter the nucleus. The nuclear envelope begins to break up into small vesicles, and the Golgi apparatus and endoplasmic reticulum fragment and disperse to the periphery of the cell. The nucleolus disappeared. centrosomes begin to move to opposite poles of the cell. The microtubules that form the base of the mitotic spindle extend between the centrosomes, pushing them apart as the microtubule fibers elongate. The sister chromatids begin to shrink tighter and become visible under a light microscope.
Draw A Neat Labelled Diagram Of Cell Cycle
During prometaphase, many processes that began in prophase continue to progress and culminate in the formation of connections between chromosomes and the cytoskeleton. The rest of the nuclear package has disappeared. The mitotic spindle continues to develop as additional microtubules assemble and stretch across the length of the former nuclear area. Chromosomes become condensed and visible. Each sister chromatid is attached to spindle microtubules at the centromere through a protein complex called a kinetochore.
During metaphase, all the chromosomes are aligned in a plane called the metaphase plate, or equatorial plane, midway between the two poles of the cell. Sister Komath is still closely attached. At this time, the chromosomes are maximally condensed.
During anaphase, the sister chromatids in the equatorial plane are separated at the centroid. Each chromatid, now called a chromosome, is quickly pulled to the centrosome where its microtubule is attached. Cells visibly expand when non-kinetochore cells slide together at the metaphase plate where they overlap.
During telophase, all the events that set up duplicated chromosomes for mitosis during the first three phases are reversed. Chromosomes reach opposite poles and begin to separate (segregate). The mitotic spindles are separated into monomers that will be used to assemble the components of the cytoskeleton for each daughter cell. The nuclear envelope surrounds the chromosomes.
Solution: Cell Cycle Stages Images And Description
This page of the film shows the different aspects of mitosis. Watch the movie titled “DIC Microscopy of Cell Division in a New Lung Cell” and identify the stages of mitosis.
Cytokinesis is the second part of the mitotic phase during which cell division is completed by the separation of the cytoplasmic corpuscles into two daughter cells. Although the steps of mitosis are similar for most eukaryotes, the process of cytokinesis is quite different for eukaryotes that have cell walls, such as plant cells.
In cells such as animal cells that lack a cell wall, cytokinesis begins after the onset of anaphase. A ring of actin filaments forms at the plasma membrane in the early metaphase plate. Actin filaments pull the cell’s equator inward, forming a cleft. This crack, or “crack,” is called a crack. The furrow deepens as the actin ring contracts, and eventually the membrane and cell are cut in two (Figure 6.5).
In plant cells, cleavage is impossible because of the rigid cell wall surrounding the plasma membrane. New cell walls must form between the daughter cells. During interphase, the Golgi apparatus accumulates enzymes, structural proteins, and glucose molecules before breaking up into vesicles and distributing throughout the dividing cell. During telophase, these Golgi vesicles move on microtubules to collect at the metaphase plate. There, the fuse fuses from the center to the wall; This structure is called the cell sheet. As more vesicles fuse, the cell membrane expands until it fuses with the cell wall on the side of the cell. Enzymes use the glucose accumulated between the membrane layers to create new cellulose cell walls. The Golgi membrane becomes the plasma membrane on either side of the new cell wall (Figure 6.5).
Lab 9 Mitosis Meiosis
Figure 6.5 In part (a), clefts are cracks at the former metaphase plate in an animal cell. The plasma membrane is pulled into a ring of actin filaments that contract in the membrane. The pore cracks deepen until the cells are squeezed in two. In part (b), Golgi vesicles coalesce at the former metaphase plate in plant cells. vesicles fuse and form cell sheets. Cell plates grow from the center to the cell wall. A new cell wall is made from the vesicle contents.
Not all cells follow the classical cell cycle model in which newly formed daughter cells enter interphase, closely followed by the mitotic phase. Cells in G
Phase not seriously prepared to divide. Cells are in the quiescent (dormant) phase, having exited the cell cycle. Some cells enter G
. Other cells that never or rarely divide, such as heart muscle and growing nerve cells, remain in G
Make Like A Cell And Split: Comparing Mitosis And Meiosis
Figure 6.6 A cell that is not actively preparing to divide enters a reserve phase called G0. In some cases, this is a temporary condition until it induces entry into G1. In other cases, the cell will be in G0 permanently.
The length of the cell cycle is highly variable even within cells of individual organisms. In humans, the frequency of cell turnover ranges from a few hours in early embryonic development to an average of two to five days for epithelial cells, or throughout the human lifespan used in G.
By special cells such as cortical or cardiac neurons
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