bell work what is the difference between mitosis and meiosis?
DESCRIPTION
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei.TRANSCRIPT
Bell Work
• What is the difference between mitosis and meiosis?
Lecture 35
Mitosis
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: G1 (first gap), S (synthesis), and G2 (second gap).
• A cell grows (G1), continues to grow as it duplicates its chromosomes (S), grows more and prepares for mitosis (G2).
• 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