Post on 13-Dec-2015
5.2 Mitosis
•Describe Interphase•Know the phases of mitosis•Know Cytokinesis
Cell Cycle
1. Interphase2. Mitosis3. Cytokinesis
Interphase (cell cycle)
• Not dividing• Growth and preparation
Interphase (cell cycle)
1. G1 (gap 1) – growth2. S (synthesis) – chromosomes
replicate3. G2 (gap 2) –new organelles
Interphase
Chromosome replication1. Chromatin coils/ twists to form a
chromosome2. Chromosome makes a copy3. Sister chromatids formed
Question:Question:What is a What is a chromosomechromosome??
Answer:Answer:
• A chromosomechromosome is made up of a DNADNA - histone protein histone protein complex called chromatinchromatin.
• ChromatinChromatin is a long, thin fiber that is folded and coiled to form chromosomeschromosomes.
DNA double helix
Histone proteins
chromosome
Question:Question:
• What is a replicated What is a replicated chromosomechromosome??
Answer:Answer:
• A replicated chromosomechromosome consist of two strands of identical chromosomal material called chromatidschromatids (sister sister chromatidschromatids).
chromatid
chromatid
S phase: chromosomes replicate
chromosome
chromosome
centromere
Question:Question:
• When is a When is a chromatid a chromatid a chromatidchromatid??
Answer:Answer:
• A chromatidchromatid is a chromatidchromatid as long as it is held in association with a sistersister chromatidchromatid at the centromerecentromere.
chromatid
chromatid
centromere
chromosome
Mitosis
Follows Interphase in the cell cycle1. Prophase2. Metaphase3. Anaphase4. Telophase
Prophase - 1
• Nuclear membrane breaksdown• Centrioles move to poles• Spindle fibers form• Sister chromatids are held together
centromeres
Metaphase -2
• Centromeres attach to fibers• Pull chromosomes to the center on
the “metaphase plate”
Anaphase - 3
• Centromeres divide sister chromatids• Chromatids move to opposite poles
of the cell
Telophase - 4
• Chromosome fully divided into 2 new cells
• 2 nuclei and nuclear membrane form• Chromosomes uncoil to form
chromatin
Cytokinesis
• Follows mitosis in the cell cycle• Cytokinesis = division of cytoplasm• Cell membranes start to split• 2 new cells are formed
Cytokinesis – Animal
• Animal cell – pinches off its membrane to form 2 new cells
• 24 hours after fertilization
• Plant cell – Cell wall is being formed between 2 plant cells
• Cell plate forms new cell membranes
Cytokinesis - plant
• Plant cell – Cell wall is being formed between 2 plant cells
• Cell plate forms new cell membranes