Upload
ralph-goley
View
223
Download
2
Tags:
Embed Size (px)
Citation preview
• Cell Division and Mitosis
• -Chapter 9-
• Honors Biology Program• Mountain Pointe High School
Development Of A Human Hand
future arm and hand of embryo, five weeks old
Overview: Key Roles of Cell Division
• Reproduction distinguishes living from non-living• Multicellular organisms develop from a zygote.• Cell division aids in repair & renewing of cells
Overview: Key Roles of Cell Division
• Cell division results in genetically identical daughter cells.• Exact copy in each daughter cell.• A cells genetic information, package in DNA, is called its genome.• In prokaryotes DNA a long single strand• Eukaryotes several DNA molecules.
Overview: Key Roles of Cell Division
• In meiosis gametes are produced (egg & sperm cells).• Meiosis yields 4 non-identical daughter cells with ½ the number of chromosomes.
The Cell CycleEukaryotic cells
divide in a series of steps known as the Cell Cycle.
Three main parts:
(a) Interphase
(b) Mitosis
(c) Cytokinesis
End result: two genetically identical “daughter cells”.
InterphaseInterphase
• It’s important to understand that
during Interphase, no division is taking
place!• Interphase is divided into three
stages:• G1
• S• G2
InterphaseInterphase• G1 phase, the cell grows
and protein production is high.
• S phase, DNA is replicated. Chromosomes aren’t visible, since the DNA is in the form of chromatin.
• The number of cytoplasmic components is doubled.
nucleus
cytoplasm
cytoplasm
DNA ReplicationDNA Replication
one chromosome (unduplicated)
one chromosome (duplicated)
one chromatid
sister chromatid
CENTROMERE
• “S” stage of Interphase, DNA must copy itself so that each new daughter cell will have its own copy of the genetic code.
• The two sister chromatids are held together by a centromere.
Chromosome Structure
Kinetochore
One nucleosome
DNA
Attached to both sides of a centromere are connecting points
known as kinetochores.
These function as attachment points for the spindle
microtubules.
This diagram shows how DNA wraps around protein spools known as histones. A histone & its DNA
together are known as a nucleosome.
MitosisMitosis
• The process of the nucleus dividing is known as “mitosis”.
• Mitosis has four stages: Prophase, Metaphase, Anaphase and Telophase.
EARLY PROPHASE
LATE PROPHASE LATE PROPHASE
ProphaseProphaseThe first stage of mitosis is
prophase.
Chromatin condenses and coils into visible chromosomes.
Nucleolus & nuclear envelope disintegrate.
Spindle apparatus starts to form between centrioles.
Centrioles (found only in animal cells) begin moving to
opposite ends of the cell.
• MetaphaseMetaphase
The shortest stage of mitosis is metaphase.
During this phase, the sister chromatids are
arranged at the equator of the cell.
The spindle microtubules attach to
the kinetochores of each chromatid.
• During anaphase, the two sister
chromatids are separated from each other by the spindle
microtubules and moved to opposite
poles.• Once separated, they
are referred to as chromosomes, not
chromatids.
AnaphaseAnaphase
• The final stage of mitosis is telophase.
• Chromosomes uncoil into chromatin.
• Nucleoli & nuclear envelopes reappear.
• Spindle microtubules disintegrate.
TelophaseTelophase
• The division of the cytoplasm is known as cytokinesis.
• Cytokinesis is the final step in the Cell Cycle.
CytokinesisCytokinesisIn animal cells, a cleavage furrow forms, microfilaments contract and cut the cell in two.
• In plant cells, the cell wall prevents the cell from being pinched in two.
• Instead, a “cell plate” forms between the two nuclei.• Cellulose deposits begin to form at the cell plate, forming a crosswall
that divides the parent cell into two daughter cells.
CytokinesisCytokinesis