Table of Contents
Meiosis : Type of Meiosis Division-
Meiosis is a type of cell division which results in the creation of four genetically diverse daughter cells, each with half the number of chromosomes of the parent cell. The process of meiosis begins with the replication of the cell’s chromosomes, followed by two rounds of division in which the chromosomes are divided equally between the daughter cells.
Meiosis I:
In meiosis I, the pairs of chromosomes line up in the middle of the cell. The DNA in each chromosome is then copied, so that each new chromosome has two copies. The copies then split down the middle, and the cell divides in two, giving each new cell two copies of each chromosome.
A. Prophase I:
Prophase I is the first stage of meiosis. During prophase I, the chromosomes condense and the nuclear envelope breaks down. The spindle apparatus forms and the chromosomes attach to the spindle fibers.
B. Metaphase I:
Metaphase I is when the chromosomes are lined up in the middle of the cell.
C. Anaphase I:
Anaphase I is when the chromosomes are pulled apart and move to the opposite ends of the cell.
D. Telophase I:
Telophase I is when the chromosomes reach the ends of the cell and the cell divides.
E. Prophase II:
Prophase II is the second stage of meiosis. During prophase II, the chromosomes become less condensed and the nuclear envelope reforms. The spindle apparatus disappears and the chromosomes are no longer attached to the spindle fibers.
F. Metaphase II:
Metaphase II is when the chromosomes are lined up in the middle of the cell.
G. Anaphase II:
Anaphase II is when the chromosomes are pulled apart and move to the opposite ends of the cell.
H. Telophase II:
Telophase II is when the chromosomes reach the ends of the cell and the cell divides.
B. Prometaphase II:
The second stage of meiosis is prometaphase II, which is marked by the breakdown of the nuclear membrane. This allows the chromosomes to move freely within the cell. The spindle fibers also form at this time and attach to the chromosomes.
C. Metaphase I:
metaphase I is the phase of meiosis in which the chromosomes are aligned in the middle of the cell. this is done by the spindle fibers that are attached to the chromosomes. the chromosomes are then pulled to the opposite ends of the cell.
D. Anaphase I:
In anaphase I, the sister chromatids are pulled apart by the spindle fibers and migrate to opposite poles of the cell. The cell membrane pinches in between the two sets of chromosomes to create two daughter cells.
E. Telophase I:
The chromosomes have uncoiled and the nuclear envelope has disappeared. The chromosomes are now spread out in the cytoplasm.
: E. Telophase I: The chromosomes have uncoiled and the nuclear envelope has disappeared. The chromosomes are now spread out in the cytoplasm. F. Telophase II: Two new nuclear envelopes have formed and the chromosomes are now located in separate nuclei.
F. Cytokinesis I:
cytokinesis in animal cells
A. Overview
Cytokinesis is the process by which animal cells divide to produce two daughter cells. It is a complex process that is regulated by a variety of proteins, including the protein kinases Cdk1 and Cdk2.
B. The role of Cdk1 and Cdk2
Cdk1 and Cdk2 are protein kinases that play a critical role in regulating cytokinesis. They are activated by the protein kinase, M-phase-promoting factor (MPF), which is in turn activated by the protein kinase, cdk-activating kinase (CAK).
C. The role of the actin cytoskeleton
The actin cytoskeleton plays a crucial role in cytokinesis. It is responsible for the formation of the contractile ring, which is a ring of proteins that contracts to pull the cell membrane together and divide the cell.
Meiosis II:
Crossing-over
chromosome
pair
crossing-over
genes
alleles
In meiosis II, crossing-over occurs between homologous chromosomes. This is when the two chromosomes exchange genetic information. This can result in new combinations of alleles, which can lead to variation in the offspring.
A. Prophase II:
Chromosomes condense and the nuclear envelope breaks down
B. Metaphase II: Chromosomes line up in the center of the cell
C. Anaphase II: Chromosomes are pulled apart and move to opposite ends of the cell
D. Telophase II: The cell divides and two new cells are formed
B. Metaphase II:
The chromosomes line up in the middle of the cell
C. Anaphase II: The chromosomes are pulled apart to opposite ends of the cell
D. Telophase II: The cell divides, and each new cell has a complete set of chromosomes
C. Anaphase II:
The chromosomes separate.
D. Telophase II: The cell divides, and two daughter cells are formed.
D. Telophase II:
The chromosomes have been divided into two daughter cells.
E. Cytokinesis: The cytoplasm of the cells has divided, and the daughter cells are now separate.
E. Cytokinesis II:
The Cell Plate
1. Formation of the cell plate
2. Cell plate growth
3. Cell plate dissolution
4. Summary
1. Formation of the cell plate
In animal cells, cytokinesis is the process of dividing the cell into two daughter cells. This is accomplished by the formation of a cell plate, which is a thin membrane that grows between the two daughter cells. The cell plate is formed by the fusion of the plasma membranes of the daughter cells.
In plant cells, cytokinesis is the process of dividing the cell into two daughter cells. This is accomplished by the formation of a cell plate, which is a thin membrane that grows between the two daughter cells. The cell plate is formed by the fusion of the plasma membranes of the daughter cells and the formation of a cell wall between the two daughter cells.
2. Cell plate growth
The cell plate grows by the addition of membrane proteins and lipids from the plasma membranes of the daughter cells. These proteins and lipids are transported to the cell plate by vesicles that fuse with the plasma membranes of the daughter cells.
3. Cell plate dissolution
The cell plate dissolves by the degradation of the membrane proteins and lipids that it contains. This degradation is accomplished by enzymes that are located in the plasma membranes of the daughter cells.
4. Summary
In animal cells, cytokinesis is the process of dividing the cell
