Cell division

PROPHASE

PROPHASE

At the onset of mitosis, the nuclear membrane of a cell is intact and as this stage progresses, the nuclear membrane disappears

PROPHASE

In the nucleus, the chromatin material becomes tightly coiled as it condenses into discrete chromosomes

PROPHASE

The condensed chromosomes appear as two identical sister chromatids united along the centromere, or kinetochore

PROPHASE

The mitotic spindle in the cytoplasm starts to form. (The spindle f ibers composed of microtubules)

PROPHASE

Centrioles move away from each other and toward the opposite poles. This is propelled by the lengthening bundles of microtubules found between them

METAPHASE

At this stage, the centrioles have finally reached their respective poles

METAPHASE

Chromosomes start to assemble at the imaginary plane midway between the spindle’s two poles. The centromeres of all chromosomes are aligned with one another, and sister chromatids of each chromosome are assembled at the equator of the cell

METAPHASE

The centromeres of the sister chromatids face the opposite poles of the cell. Thus, the identical chromatids of each chromosomes are attached to the microtubules radiating from the opposite poles of the cell. The spindle fibers are very abundant during this stage

ANAPHASE

This starts when the paired centromeres of each chromosome separate. This way the sister chromatids start to move away from each other. Each sister chromatid is now considered a full-fledges chromosome.

ANAPHASE

The sister chromatids the begin to move along the microtubules at the point of attachment the centromere toward the opposite poles of the cell

ANAPHASE

This movement is usually referred to as “the dancing of the chromosome” by some biologists

ANAPHASE

the two poles of the cell have an equal and complete set of chromosomes

TELOPHASE

The daughter nuclei start to form at the two poles of the cell, where the chromosomes have been assembled

TELOPHASE

Nuclear membrane start to reappear and are reconstructed from the fragments of the cell’s former nuclear envelop

TELOPHASE

The nucleoli reappear, and the chromatin fiber of each chromosome uncoils

TELOPHASE

The division of the nucleus into two genetically identical nuclei is now complete (karyokinesis). This is followed by cytokinesis, the division of the cytoplasm into two, eventually forming two new daughter cells. This is the last part of mitosis

PROPHASE 1

Each chromosome is now composed of two sister chromatids held together by the centromere, and this is called a dyad

PROPHASE 1

Synapses, or pairing of homologous chromosomes, takes place here. The homologous chromosomes have same length, staining pattern, and position of the centromere. One homologous chromosome come from the father and the other from the mother; a paired homologous chromosomes is composed of four sister chromatids and is popularly called a tetrad

Main event of in prophase 1

crossing-over

METAPHASE 1

the paired homologous chromosomes (tetrads) line up along the m equatorial plate of the cell

METAPHASE 1

Spindle fibers increase in number. This is the part where the kinetochore of chromosomes will attach to facilitate movement

ANAPHASE 1

Homologous chromosomes separate and migrate toward the respective poles. However the centromeres don’t divide, and the chromosomes remain dyads

ANAPHASE 1

In humans, since there 46 chromosomes, 23 will move to each pole, which means that only one half of the number of chromosomes will remain in each cell

METAPHASE II

The two kinetochores of each centromere bind to spindle fibers from opposite poles

ANAPHASE II

Centromeres divide, allowing microtubules attached to the kinetochores to pull the sister chromatids apart

ANAPHASE II

The sister chromatids are now called sister chromosomes as they move toward the opposite poles

TELOPHASE II

Nuclear envelopes reform, and the cell plate eventually produces a total of two daughter cells, each with a haploid set of chromosomes. Since there are two cells undergoing Meiosis II, at the end if this process, a total of 4 new cell are produced.