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Cell Cycle- Chapter 12

Image Credits: Biology (Campbell) 9th edition, copyright Pearson 2011, & The Internet.

Sara Mitchell

on 8 March 2016

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Transcript of Cell Cycle- Chapter 12

Cell Division
Big Questions:
Make Sure You Can:
Why Divide?
The Cell Cycle
The "continuity of life"
In order to survive, the individual must replace damaged cells
In order to grow, cell production must be greater than cell death
In order to survive, the species must replace individuals
Cell division accomplishes these purposes!
A dividing amoeba
A dividing bone marrow cell
A dividing sea urchin embryo
The Phases of a Cell's Life
G1- Growth
S- DNA replication
G2- Preparation for division
M - Mitosis

G0- Non-dividing state (most cells in you)
Very tightly controlled (why?)
Tightly coiled pieces of DNA that condense prior to division
Prokaryotes only have one, circular chromosome

Eukaryotes have many, linear chromosomes
Most eukaryotic cells have 2 copies of every chromosome

They form in attached, identical pairs

Chromatid: one member of the pair
Centromere: region where they are joined
S phase
Make sure you understand the chromosome, chromatid relationship

It can be confusing...
Haploid vs. Diploid
1 copy of every chromosome (n)
2 copies of every chromosome (2n)
Human cells have 23 pairs of chromosomes

How many chromatids are present during:
Chromosomes condense
Nuclear envelope breaks down
Mitotic spindle begins to form
Animal cells: centrioles divide
Chromosomes begin to migrate to cell equator
2 complete spindles at cell poles
Chromosomes are at metaphase plate
Spindle attaches to "kinetochore" of chromosomes at centromere
Chromatids split apart at centromere
Migration of chromatids to cell poles mediated by the kinetochore
Chromosomes decondense
Nuclear envelope reforms
Cytokinesis: cell membrane divides
Replication of DNA
Preparation for division

Most of a cell's life cycle
Newt, Whitefish, Onion
Differences between plant-like and animal-like cells (Why?)
A "contractile ring" of microfilaments pinches the cell in 2
Vesicles from both cells deposit a new cell wall partition ("cell plate") in the middle of the cell
Organelle apportionment is essentially random!
Mitosis at a Glance
The Evolution of Mitosis
There are more similarities between eukaryotic and prokaryotic cell division than might be apparent at first glance

Proteins involved in binary fission & eukaryotic cell division have a
large degree of homology
Some unicellular eukaryotes demonstrate "intermediate" modes of division
Binary fission in bacteria
(aka "rolling circle replication")
Let's play "spot the phases"
"Non-Reductive" Eukaryotic Cell Division
Describe the roles that mitosis plays in eukaryotic organisms.

Explain how mitosis produces two genetically identical cells.

Explain how interphase prepares a cell for mitosis.

Explain why many cells never divide.

Explain the function of each stage of mitosis.

Compare the events of mitosis in plant-like and animal-like cells.
Why do cells need to divide?

How does cell division provide for continuity of life processes in an individual and in a species?
"Binary Fission"
The splitting of the cell into two due to the cell membrane pinching off
Full transcript