Download Mitosis and the Cell Cycle

2.5 Cell Division
How you got from one to trillions!!
Conception
• All animals begin
as a fertilised egg
cell (a zygote)
Image Credit: Zygote
Then it divides…
Image Credit: www.ehd.org/
… and divides
Released into the Public Domain by Jrockley
Until it becomes an embryo
Image Credit: www.scienceclarified.com
Cell Cycle
2.5.1
• Interphase
•
•
•
•
Longest phase (94%)
G1: Cell growth
S: Replication of DNA
G2: Growth for division of cell
• Mitosis
• Division of nucleus and
chromosomes
• Cytokinesis
• Division of cytoplasm and
organelles into two daughter
cells.
Cell cycles are not uniform
Cell type
Bean root tip
Cell cycle / h
19.3
Mouse fibroblast
22
Chinese hamster fibroblast
11
Mouse small intestine
epithelium
Mouse esophagus epithelium
17
© 2010 Paul Billiet ODWS
181
Mitosis Cell Basics
• Somatic (body) cells.
• Diploid (2n): one
chromosome from
each parent. (n=23)
• Duplicated
chromosomes have 2
sister chromatids.
• Attached at
centromere in the
middle.
Both are called chromosomes!!
Mitosis
• Responsible for
cellular:
•
•
•
•
Growth
Embryonic development
Tissue repair
Asexual Reproduction
2.5.6
Interphase
• Active period.
• Many metabolic
reactions occur,
including protein
synthesis.
• Increase in number of
mitochondria and/or
chloroplasts.
• Most important: DNA
replication while
chromatin. S phase.
2.5.3
Interphase
Prophase
• Preparing.
• Supercoiling of
chromosomes
(condense)
• Nuclear membrane
and nucleolus
disappear.
2.5.4
Prophase
Metaphase
• Meet in the Middle.
• Attachment of spindle
microtubules to
centromeres, one from
each centriole.
• All chromosomes are
lined up at the middle,
also called the equator.
• Equal pulling from
opposite ends.
2.5.4
Metaphase
Anaphase
• Moving away
• Centromeres split.
• Sister chromatids are
pulled to opposite poles
by spindle fibers.
• Each is now considered
a chromosome.
• Two diploid cells are
forming.
2.5.4
Anaphase
Telophase
• Two nuclei.
• Chromosomes
change to chromatin.
• Nuclear membrane
reforms.
• New nucleoli form.
• Cytokinesis is usually
happening at the
same time as
telophase.
2.5.4
Telophase
Cytokinesis
• Cell membrane and
cytoplasm division.
• Two genetically identical
nuclei now found in two
diploid daughter cells.
2.5.5