Mitosis and Binary Fission Terms

Notes that Natalie and I took:

Prophase

• First stage of mitosis.

• When chromatin fibers condense and are thick enough to be seen with a microscope.

• Sister chromatids join at the centromere.

• The cell stops making ribosomes because the nucleolus disappears. 

• Mitotic spindle forms.

• Pulls chromosomes to the center of the cell for metaphase.

Metaphase

• Second stage of mitosis.

• Chromosomes are gathered in the middle of the cell in a line. 

• The chromosomes are attached to spindles microtubules.

Anaphase

• Third stage of mitosis.

• The sister chromatids separate from their partners making them each a daughter chromosome. 

• Proteins at the centromeres move the daughter chromosomes along the spindle microtubules toward the poles of the cell. 

• Spindle microtubules that are not attached to centromeres, do the opposite, and push the poles further apart.

Telophase 

• Final stage of mitosis is telophase.

• When chromosomes reach the poles of the spindle.

• Everything that occurred in prophase is reversed.

• The spindle disappears, and two nuclear envelopes appear and form around each set of daughter chromosomes. 

• Chromosomes uncoil and lengthen, reforming the nucleoli.

• Mitosis is done.

Cytokinesis

• Completes cell division, by dividing cytoplasm into two daughter cells, creates a cell wall only in plant cells

• Usually occurs along with telophase.

Notes that Shirali and Aariz took:

• Interphase G₁:

  • First change/gap, the cell increases in growth and gathers building blocks with the proteins and energy reserves so it can replicate each chromosome in the nucleus

• Interphase S:

  • process where the cell spends most of its time growing and replicating its DNA

• Interphase G₂:

  • The final phase of interphase, where the cell actively prepares for mitosis by synthesizing proteins, growing further, and organizing the replicated DNA in readiness for cell division

  • The process where a single cell divides into two genetically identical daughter cells

• Prophase: chromosomes condense and become visible, the nuclear membrane breaks down, and spindle fibers form

• Prometaphase: Divides the duplicate genetic material in a parent cell into two daughter cells that are exactly alike. The nuclear envelope breaks down 

• Anaphase: Sister chromatids separate at the centromere and are pulled apart by the spindle fibers, leading them to be pulled toward opposite ends of the cell 

• Telophase: Separates the copy of genetic material held in the nucleus of a parent cell into two daughter cells. Once the duplicated paired chromosomes separate and pulled to different sides, telophase begins

• Cytokinesis: The cytoplasm splits into two equal parts and the cell divides. The plasma membrane of the parent cell pinches inward along the cell’s equator until two daughter cells form

• When cytokinesis is finished, we end up with two new cells, each with a complete set of chromosomes identical to those of a mother cell

Notes that Anushka and Anna took (binary fission —> 1 chromosome):
It is the main strategy of asexual reproduction

• Prokaryotic cells copy their DNA then divide and repeat, each division is called binary fission

• Binary fission allows for prokaryotes to reproduce very quickly in the right conditions

• Binary fission occurs in prokaryotes like bacteria and even some eukaryotes like amoeba

Binary fission in Prokaryotes like bacteria

• Step one, DNA replication: the bacteria duplicates its chromosome and has each copy attached to a separate location of the cell membrane 

• Step two, cell elongation: since the chromosomes are in two different locations on the cell membrane they separate from each other and cause the cell to stretch itself. This prepares it for division and begins to form two identical circular DNA molecules that are called sister chromatids

• Step three, Invagination and formation of the septum: the cell membrane will pinch inward at the center and form something called a septum, a separating wall between the two future daughter cells

• Step four, cell separation: the cell finally split resulting in two identical daughter cells that will grow and continue the binary fission process

Binary fission in Eukaryotes like Amoeba

Step 1:Amoeba, like bacteria, is a unicellular cell. The cell grows to a particular size for the division. 

Step 2: The nucleus in the amoeba divides through the Mitosis process. Inside the nucleus the chromatin condenses and the nuclear line disintegrates and separates. Separating the chromosomes creates two daughter nuclei

Step 3: Once the genetic DNA and material replicates the cytoplasm in the cell divides into two same sized daughter cells. The cleavage of the cell deepens due to the splitting of the parent cell into two. 

Step 4: The cell splits up into two identical daughter cells with the similar copy of a parent nucleus and cytoplasm.

when would a cell divide? (animal cell mitosis)

• when we’re growing or healing

• making more skin, hair, nails, blood cells

• brain and spinal cord cells can’t undergo mitosis