5.2 Mitosis and Cytokinesis
LEQ: How do eukaryotic cells divide?
• Key terms – interphase, chromosome, chromatin, phases
of mitosis (various), cytokinesis
• Reading 5.3
5.2 Mitosis and Cytokinesis
LEQ: How do eukaryotic cells divide?
• Activator:
• During which stage of the cell cycle is DNA copied?
Explain how this process occurs.
5.2 Mitosis and Cytokinesis
5.2 Mitosis and Cytokinesis
Chromosomes condense at the start of mitosis.
• A chromosome is a DNA molecule associated with protein.
• DNA wraps around histone proteins that condense it.
DNA double
helix
DNA and
histones
Chromatin
Supercoiled
DNA
• Chromosomes come in duplicated
and unduplicated forms
5.2 Mitosis and Cytokinesis
chromatid
• Chromatin – DNA coiled around
histone proteins
• Chromatid - One half of a
duplicated chromosome
• Sister chromatids (duplicated,
right) - are held together at the
centromere.
• Telomeres (ends) - protect DNA
and do not include genes.
telomere
centromere
telomere
Condensed, duplicated chromosome
5.2 Mitosis and Cytokinesis
5.2 Mitosis and Cytokinesis
Focus on Mitosis:
• The nucleus – when is it disassembled, when does it
reappear?
• Chromosomes – how do they move, when do chromatids
separate?
• Mitotic Spindle – how does it assist in mitosis?
5.2 Mitosis and Cytokinesis
Mitosis and cytokinesis produce two genetically identical
daughter cells in many eukaryotes.
Parent cell
• Interphase prepares
the cell to divide.
– G1
–S
– G2
centrioles
spindle fibers
centrosome
nucleus with
DNA
5.2 Mitosis and Cytokinesis
• Mitosis divides the cell’s nucleus in four phases:
– Prophase - chromosomes condense, nucleus
disassembles, spindle fibers form.
5.2 Mitosis and Cytokinesis
– Metaphase - chromosomes line up in the middle of
the cell.
5.2 Mitosis and Cytokinesis
– Anaphase: sister chromatids separate, move to
opposite sides of the cell.
5.2 Mitosis and Cytokinesis
Focus: Anaphase chromosomes
5.2 Mitosis and Cytokinesis
– Telophase - nuclei form, spindle disassembles and
chromosomes begin to uncoil.
5.2 Mitosis and Cytokinesis
• Cytokinesis differs in animal and plant cells.
– Animals: the
membrane pinches
closed.
– Plants: a cell wall
forms.
5.2 Mitosis and Cytokinesis
5.2 Mitosis and Cytokinesis
5.2 Mitosis and Cytokinesis
5.2 Mitosis and Cytokinesis
A look ahead: Lab
• Interphase
• “I-ball”
Parent cell
centrioles
spindle fibers
centrosome
nucleus with
DNA
5.2 Mitosis and Cytokinesis
• Prophase
• “pile”
5.2 Mitosis and Cytokinesis
• Metaphase
• “middle”
5.2 Mitosis and Cytokinesis
• Anaphase
• “apart”
5.2 Mitosis and Cytokinesis
• Telophase
• “two piles”
5.2 Mitosis and Cytokinesis
Summary:
• Briefly explain why the daughter cells resulting from
binary fission and mitosis are genetically identical to each
other and to the original cell.
• How does mitosis accomplish the production of daughter
cells.
– Be sure to address how genetic information is
acquired
5.2 Mitosis and Cytokinesis
Answers:
• Daughter cells are clones, the genetic information of the
parent cell was copied and condensed into duplicated
chromosomes, each consisting of two identical DNA
molecules (sister chromatids). The chromatids are then
separated during metaphase so that when the daughter
cells begin to assemble their nuclei, each will have
received a complete copy of the parent cell’s genetic
information.
• Prophase and telophase are opposites. The nuclear
envelope fragments, chromosomes condense, and
spindle fibers start to assemble in prophase. In
telophase, the reverse occurs: the nuclear envelope
reforms, chromosomes uncoil, and spindle fibers
disassemble.