Bell Work What is the difference between mitosis and meiosis?

Lecture 35 Mitosis

Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei.

Mitosis It is followed immediately by cytokinesis.

Cytokinesis Divides the nuclei, cytoplasm, organelles, and cell membrane into two separate cells containing roughly equal parts of these cellular components.

Mitosis Mitosis occurs only in eukaryotic cells. Prokaryotic cells, which lack a nucleus, divide by a process called binary fission.

Significance of Mitosis Development and growth Cell replacement Regeneration Asexual reproduction

A Short Summary of Mitosis During mitosis the pairs of chromatids condense and attach to fibers that pull the sister chromatids to opposite sides of the cell. The cell then divides in cytokinesis, to produce two identical daughter cells which are still diploid cells.

The Result of Mitosis The primary result of mitosis is the transferring of the parent cell's genome into two daughter cells. These two cells are identical and do not differ in any way from the original parent cell.

Mitosis Copies Chromosomes The genome is composed of a number of chromosomes. Because each daughter cell is genetically identical to the parent cell, the parent cell must make a copy of each chromosome before mitosis.

What are Chromosomes? Tightly-coiled DNA that contain genetic information vital for proper cell function.

The Copying of Chromosomes Occurs during the S phase of interphase

Once Copying Occurs Each chromosome now has an identical copy of itself, and together the two are called sister chromatids.

The Centromere The sister chromatids are held together by a specialized region of the chromosome: a DNA sequence called the centromere.

The Stages of Mitosis These stages are prophase, metaphase, anaphase and telophase.

Interphase Three phases: G 1 (first gap), S (synthesis), and G 2 (second gap). A cell grows (G 1 ), continues to grow as it duplicates its chromosomes (S), grows more and prepares for mitosis (G 2 ). Chromosomes are replicated only during the S phase.

Interphase Not part of mitosis In the S phase, DNA is copied

Prophase At the onset of prophase, chromatin fibers become tightly coiled, condensing into discrete chromosomes. Since the genetic material has already been duplicated earlier in S phase, the replicated chromosomes have two sister chromatids, bound together at the centromere.

Also During Prophase Centrosomes (consisting of a pair of centrioles, and actin, and a halo of microtubule fragments) are pushed to opposite sides of the cell. Microtubules act as cellular ropes or poles

Prophase Chromatin condenses

Metaphase The two centrosomes start pulling the chromosomes through their attached centromeres towards the two ends of the cell. The centromeres of the chromosomes line up along the metaphase plate or equatorial plane, an imaginary line that is right in between the two centrosome poles. This line is called the spindle equator.

Metaphase Chromosomes line up in the middle

Anaphase The proteins that bind sister chromatids together are cleaved. These sister chromatids now become separate daughter chromosomes, and are pulled apart by shortening the microtubules and move toward the respective centrosomes to which they are attached. The cleaved centromeres go first while the chromatids trail behind.

Anaphase Chromosomes pull apart (two sister chromotids each containing information)

Telophase Corresponding daughter chromosomes attach at opposite ends of the cell. A new nuclear membrane, using the membrane vesicles of the parent cell's old nuclear membrane, forms around each set of separated daughter chromosomes (though the membrane does not enclose the centrosomes) Both sets of chromosomes, now surrounded by new nuclei, begin to "relax" or decondense back into chromatin. Mitosis is complete, but cell division is not.

Telophase Two new nuclei form

Cytokinesis Cytokinesis is a separate process that begins at the same time as telophase. Cytokinesis is technically not even a phase of mitosis, but rather a separate process, necessary for completing cell division.

Digital Mitosis Flip Book