M Phase of the Cell Cycle
Summary
TLDRThis lesson covers the M phase of the cell cycle, focusing on mitosis and cytokinesis. It reviews the cell cycle phases: G1, S, G2 (interphase), and M (cell division). Mitosis is divided into four stages: prophase (chromosomes form, nuclear membrane disappears), metaphase (chromosomes align at the cell equator), anaphase (sister chromatids separate and move to poles), and telophase (nuclear membranes reform). Cytokinesis follows, dividing the cytoplasm to form two identical daughter cells. In animal cells, this occurs by pinching the cell membrane; in plant cells, a cell plate forms. The M phase results in two identical daughter cells.
Takeaways
- 🔬 The M phase of the cell cycle includes mitosis and cytokinesis, representing cell division.
- 📅 The G1, S, and G2 phases make up interphase, while the M phase follows as the final phase.
- 🔄 Mitosis, the division of the nucleus, is broken down into four phases: prophase, metaphase, anaphase, and telophase.
- 🧬 During prophase, chromatin condenses into chromosomes, and the nucleolus and nuclear membrane disappear.
- 📏 In metaphase, spindle fibers align the chromosomes along the cell's equator, creating an end-to-end alignment.
- 🔗 Anaphase involves spindle fibers separating sister chromatids at their centromeres, pulling them to opposite poles.
- 🎯 Telophase sees the reformation of the nuclear membrane around each set of chromosomes and the nucleolus becoming visible again.
- 🧩 Cytokinesis, the division of the cytoplasm, completes the M phase, resulting in two identical daughter cells.
- 🌱 In animal cells, cytokinesis occurs through the inward pinching of the cell membrane, while in plant cells, a cell plate forms due to the rigid cell wall.
- 📚 Key points: The M phase ends with two daughter cells identical to each other and the original cell, comprising mitosis (nucleus division) and cytokinesis (cytoplasm division).
Q & A
What are the phases of the cell cycle mentioned in the script?
-The phases of the cell cycle mentioned are G1, S, G2 (collectively known as interphase), and the M phase (mitosis and cytokinesis).
What occurs during the M phase of the cell cycle?
-During the M phase, cell division occurs through two processes: mitosis (division of the nucleus) and cytokinesis (division of the cytoplasm).
What happens during prophase in mitosis?
-During prophase, chromatin condenses into chromosomes, the nucleolus disappears, spindle fibers begin to form, and the nuclear membrane dissolves.
How are chromosomes arranged during metaphase?
-During metaphase, spindle fibers align the chromosomes along the equator of the cell, with each sister chromatid on opposite sides.
What is the role of spindle fibers in anaphase?
-In anaphase, spindle fibers shorten and separate the sister chromatids at their centromeres, pulling them toward opposite poles of the cell.
How does telophase differ from the other phases of mitosis?
-In telophase, a nuclear membrane reforms around each set of chromosomes, which then disperse into chromatin. The nucleolus also becomes visible again, marking the end of mitosis.
What is cytokinesis, and how does it differ between animal and plant cells?
-Cytokinesis is the division of the cytoplasm. In animal cells, it occurs through the inward pinching of the cell membrane, while in plant cells, a cell plate forms along the equator, eventually developing into a new cell wall.
Why can't plant cells undergo cytokinesis through the same mechanism as animal cells?
-Plant cells have a rigid cell wall that prevents the inward pinching of the cell membrane, so they form a cell plate to divide the cytoplasm.
What are centrioles, and how do they differ from centromeres?
-Centrioles are structures at the poles of the cell where spindle fibers originate. Centromeres are the regions on chromosomes where sister chromatids are attached.
What is the end result of the M phase of the cell cycle?
-The M phase results in the formation of two identical daughter cells, each with a complete set of chromosomes, identical to the original cell.
Outlines
📚 Overview of the M Phase in the Cell Cycle
This paragraph introduces the M phase of the cell cycle, which includes mitosis and cytokinesis. It provides a brief review of the cell cycle, highlighting that the G1, S, and G2 phases constitute interphase, while the M phase is dedicated to cell division. Mitosis, the division of the nucleus, is broken down into four phases: prophase, metaphase, anaphase, and telophase. This sets the stage for the detailed exploration of these phases and their significance in cell division.
🔬 Prophase: Initiation of Chromosome Formation and Spindle Apparatus
This paragraph delves into prophase, the first and longest phase of mitosis. During prophase, chromatin condenses into visible chromosomes, and the nucleolus disappears. Each chromosome consists of two sister chromatids connected by a centromere. In the cytoplasm, spindle fibers begin to form from centrioles, which move to opposite poles of the cell. The nuclear membrane disintegrates, allowing the spindle fibers to attach to the centromeres of the chromosomes.
📏 Metaphase: Chromosome Alignment at the Cell Equator
In this paragraph, metaphase is described as the phase where the centrioles reach the poles of the cell, and the spindle fibers align the chromosomes along the cell’s equator. This alignment ensures that each sister chromatid is positioned on either side of the equator, preparing the cell for the next phase of mitosis.
⚖️ Anaphase: Separation of Sister Chromatids
This section explains anaphase, where the spindle fibers pull the sister chromatids apart at their centromeres. Once separated, each chromatid is considered an individual chromosome. These chromosomes are dragged toward opposite poles of the cell by the shortening spindle fibers. The paragraph also clarifies the difference between centrioles and centromeres.
🏁 Telophase: Nuclear Reformation and Chromosome Dispersal
Telophase, the final stage of mitosis, is discussed here. During telophase, a nuclear membrane reforms around each set of chromosomes, which then disperse into chromatin. The nucleolus becomes visible again, marking the end of mitosis. This phase completes the division of the nucleus, preparing the cell for the final step of cytokinesis.
🌱 Cytokinesis: Formation of Daughter Cells
This paragraph focuses on cytokinesis, the process of cytoplasmic division that follows mitosis. In animal cells, the cell membrane pinches inward, dividing the cytoplasm and forming two identical daughter cells. In plant cells, a cell plate forms along the equator, gradually developing into a new cell wall that separates the two daughter cells. The paragraph highlights that the M phase concludes with the formation of two genetically identical daughter cells.
📝 Key Takeaways: Summary) of the M Phase
The final paragraph summarizes the key points of the M phase. It reiterates that the M phase is the fourth and final phase of the cell cycle, encompassing both mitosis and cytokinesis. Mitosis is broken down into four phases—prophase, metaphase, anaphase, and telophase—each with distinct processes leading to the division of the nucleus. Cytokinesis, the division of the cytoplasm, follows, resulting in two identical daughter cells. The paragraph emphasizes that these daughter cells are identical to each other and to the original parent cell.
Mindmap
Keywords
💡M phase
💡Mitosis
💡Cytokinesis
💡Interphase
💡Prophase
💡Metaphase
💡Anaphase
💡Telophase
💡Spindle fibers
💡Centromere
💡Chromatin
Highlights
Exploring the M phase of the cell cycle, including mitosis and cytokinesis.
Review of the cell cycle: G1, S, and G2 phases make up interphase, and M phase represents cell division.
Cell division includes division of the nucleus (mitosis) and division of the cytoplasm (cytokinesis).
Mitosis is further broken down into four phases: prophase, metaphase, anaphase, and telophase.
Prophase: chromatin condenses into chromosomes, nucleolus disappears, and spindle fibers begin to form.
Chromosomes become visible as individual entities for the first time during prophase.
Centromeres attach sister chromatids together.
Spindle fibers fan out from centrioles, which move to opposite poles of the cell during prophase.
Nuclear membrane disappears, allowing spindle fibers to attach to centromeres.
Metaphase: centrioles complete their movement to poles, and spindle fibers line up chromosomes along the equator of the cell.
Anaphase: spindle fibers separate sister chromatids at their centromeres, forming individual chromosomes.
Chromosomes move to opposite poles of the cell during anaphase.
Telophase: nuclear membrane reforms around chromosomes, which spread out into chromatin.
Cytokinesis: division of the cytoplasm resulting in two identical daughter cells.
In animal cells, cytokinesis occurs through inward movement of the cell membrane.
In plant cells, cytokinesis involves formation of a cell plate along the equator.
New cell walls form between the two daughter cells in plant cells.
Mitosis and cytokinesis ensure that each daughter cell is identical to the original cell.
Transcripts
in this lesson we'll be exploring the m
phase of the cell cycle including
mitosis and cytokinesis
let's do a quick review of the cell
cycle to see where they fit in
the g1
s and g2 phases make up interphase
and the m phase represents cell division
cell division includes division of the
nucleus called mitosis
and division of the cytoplasm called
cytokinesis
mitosis is further broken down into four
phases
prophase
metaphase
anaphase
and telophase
prophase is the longest phase of mitosis
prophase is when chromatin begins to
condense into the shape of chromosomes
and the nucleolus disappears
the previously replicated dna coils
tightly into sister chromatids
for the first time you see individual
chromosomes
in the center of each chromosome a
centromere
attaches the sister chromatids together
meanwhile in the cytoplasm microtubules
known as spindle fibers begin to fan out
from two sets of paired structures
called centrioles
the spindle fibers elongate as the
centrioles begin moving to opposite
sides or poles of the cell
while this is happening the nuclear
membrane surrounding the nucleus
disappears
now that chromosomes are no longer
separated from the cytoplasm the
opposite ends of the spindle fibers can
attach to the centromeres
next the cell enters metaphase
the centrioles complete their movement
to the poles of the cell while the
spindle fibers line up the chromosomes
along the equator of the cell
the end-to-end alignment of chromosomes
results in a sister chromatid on either
side of the equator
anaphase follows metaphase
during anaphase spindle fibers separate
the sister chromatids at their
centromere
once separated from each other each
chromatid is called a chromosome
the single-stranded chromosomes form a
v-shape as the spindle fibers shorten
and drag them through the gel-like
cytoplasm
the chromosomes move to opposite poles
of the cell toward their centrioles
it's common to confuse centrioles with
centromeres which connect chromatids
remember
centrioles are at the poles
telophase is the final stage of mitosis
in telophase a nuclear membrane reforms
around each set of chromosomes
then the chromosomes spread out into
chromatin and the nucleolus becomes
visible once again
mitosis the division of the nucleus is
now complete
the final step of the m phase is
cytokinesis the division of the
cytoplasm
in animal cells cytokinesis occurs
through the inward movement of the cell
membrane
this progressively pinches the cytoplasm
until two identical daughter cells form
in contrast plant cells can't pinch into
because they have a rigid cell wall
surrounding their cell membrane
instead cell wall material assembles
along the equator forming a structure
called the cell plate
the cell plate grows until it joins with
the existing cell membrane separating
the two halves of the cell into daughter
cells
over time new cell walls form between
the two daughter cells
here are the key points to remember
the m phase is the fourth and final
phase of the cell cycle
during the m phase cell division occurs
through two processes
mitosis when the nucleus divides
and cytokinesis when the cytoplasm
divides
mitosis has four phases
during prophase chromatin condenses into
chromosomes
spindle fibers form and the nucleolus
and nuclear membrane disappear
during metaphase spindle fibers align
the chromosomes along the cell equator
in anaphase the spindle fibers separate
sister chromatids into two separate
groups of chromosomes pulling them
toward the poles
and in telophase the nucleolus and
nuclear membrane reform
the chromosomes disperse into
chromatin cytokinesis is division of the
cytoplasm
the m phase is complete after
cytokinesis occurs
the m phase of the cell cycle always
results in two daughter cells
both of these daughter cells are
identical to each other and identical to
the original cell that underwent mitosis
[Music]
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