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