Asexual Reproduction aka MITOSIS!
• In asexual reproduction, cell division results in 2 identical “daughter” cells being produced from a “parent” parent cell
• Each human cell has 46 chromosomes in its nucleus
Cell Cycle - Mitosis• 10% of cell life cycle• The cell undergoes cell division
In humans, millions of cells divide every second to maintain a total of ~60 trillion cells- some divide once a day (skin & hair), others less often (stomach lining) and some not at all (nerve & muscle cells)
Stages of Mitosis Mitosis is a continual
process, but we divide it into 4 phases
Mitosis phases:1. Prophase2. Metaphase3. Anaphase4. Telophase
Mitosis1. Prophase- chromatin condenses into
distinct duplicated chromosomes
- Nuclear membrane begins to disintegrate
- In animal cells organelles called the centrioles move to opposite sides of the cell (“poles”)
- Astral rays (microtubles) form around centrioles
Be sure to label:
1. Sister chromatids/ chromosomes2. Centrioles3. Astral rays4. Nuclear memebrane
Draw a prophase diagram
Centrioles Astral
Rays
Made of 2 sister chromatids, attached by a centromere
Nuclear membrane disintegrates
Early Prophase
Late Prophase
MitosisStep 2: Metaphase- Chromosomes line up at
equatorial plate and centromere attaches to spindle fibers that formed from elongated astral rays
- At the end of this phase the centromere splits separating the sister chromatids
- Nuclear membrane disappears
Be sure to label:
1. Centromere2. Equatorial plate3. Spindle fibers4. Centriole
Draw a diagram
Centrioles
Spindle Fibres
Equatorial Plate
Centromere
METAPHASE
Metaphase: Spindle Fibers
MitosisStep 3: Anaphase- The spindle fibers
contract, pulling the chromosomes (sister chromatids) to the opposite poles of the cell
- Centromeres divide
Be sure to include:
1. Sister chromatids2. Spindle fibres3. Centromere4. Centrioles
Draw a diagram
Centrioles
Centromere is split
ANAPHASE
MitosisStep 4: Telophase- Chromatids reach opposite poles; spindle and astral
rays disappear- Chromosomes unwind back into chromatin- Nuclear membrane begins to reform- Cell membrane pinches in the middle to divide the
cell = Cytokinesis
• Cytoplasm begins to divide by forming a cleavage furrow at the equator and pinches off
• Forming 2 daughter cells, with genetic information identical to each other
• These cells will become the new parent cells
Cytokinesis
• Cytokinesis in an animal cell
Cleavage furrow
Draw a diagram
• Be sure to liable:Part A:• Cleavage furrow• Nuclear
membranePart B:• Daughter cells• Nuclear
membrane• Chromatin
Daughter cells Chromatin
Nuclear membrane
TELOPHASE
INTERPHASE PROPHASE
METAPHASE TELOPHASE & CYTOKINESIS
Metaphase plate
Spindle Daughterchromosomes
Cleavagefurrow
Nucleolusforming
Nuclearenvelopeforming
ANAPHASE
Interphase Prophase Metaphase
Metaphase Anaphase Telophase
Animals Versus Plants• There are 2 main differences
in plant cell division
1. Plants do not contain centrioles
- They contain microtubules that create many of the same proteins (spindles), they just don’t have the centrioles
2. Plants do not undergo cytokinesis
- Instead a cell plate forms at the equator of the cell to form a new cell wall
Cytokinesis• Animal Cytokinesis Plant
CytokinesisCleavage furrow
Cell Plate