Transcript Part IV and Chapter 11 - Nicholls State University

Part IV and Chapter 11
Biology
Sixth Edition
Raven/Johnson
(c) The McGraw-Hill Companies, Inc.
Cell division increases the
number of somatic (body) cells,
and consists of:
•Mitosis (division of nucleus)
•Cytokinesis (division of
cytoplasm)
Bacteria
reproduce by
dividing
A copy of the genetic material must be made
so each new cell will have a complete
genome.
Once the DNA is copied and
moved to opposite sides of the
cell, a new cell membrane is built
to create two new cells.
Eukaryotic organisms
store their hereditary
material in chromosomes.
The total number of
chromosomes an
organism has can range
from 1 to over 1,000!
Humans have 46 total
chromosomes.
Haploid vs. Diploid
The haploid (n) number of chromosomes = the
number of types of chromosomes.
The diploid (2n) number of chromosomes = two
chromosomes of each kind.
The haploid number for humans = 23 (23 types)
The diploid number for humans = 46 (2x23)
(There are two copies of each of the 23 types of
chromosomes)
23 Types (haploid)
46 Total (diploid)
Sister chromatids –
two replicas of a
single chromosome
Centromere – the
place where sister
chromatids are
attached
Homologous chromosomes – both copies of the
same type of chromosome.
Homologous pair
for chromosome
#19
Homologous pair
for chromosome
#21
Because none of
these chromosomes
are replicated, there
are no sister
chromatids shown.
Interphase
- G1 – cell growth/organelle
replication (G0 phase = resting)
- S – synthesis of a replica of
the genome
- G2 – cell growth/organelle
replication
Mitosis
By the end of Interphase
the genome has been
replicated, new organelles
made, and the cell has
grown.
-Prophase
-Metaphase
-Anaphase
-Telophase
Cytokinesis
Cleavage Furrow
There are three
checkpoints during
the cell cycle that
ensure the cell
divides only when it
is supposed to.
When cells enter G0,
they are mature and
are not actively
dividing
Cyclin activates Cdk
(cyclin-dependent
kinase) by forming the
Mitosis-promoting factor
(MPF)
Phosphorylation of Cdk
controls the activation
and inactivation of Cdk.
Cdk in turn activates
other enzymes
responsible for getting
the cell through
checkpoints.
Multicellular organisms need
more control over cell division
than single celled organisms
Growth factors are external
signals the cell receives that
promote cell growth and division
Platelet-derived growth
factor (PDGF) is released
when blood clots and
signals the surrounding
cells to begin growing.
Over 50 different
proteins have been
identified as growth
factors – more exist!
Normal P53 either
repairs damaged DNA
or triggers the
destruction of a cell
with unrepairable
DNA.
Abnormal P53 loses
its ability to recognize
damaged DNA, so
damaged cells may
continue to divide.
Cancer – unregulated
cell growth.
Proto-oncogenes are involved with stimulating cell
division and can undergo mutations to become
cancer-causing oncogenes, which are
responsible for uncontrolled cell growth.
Tumor-suppressor genes are involved with
suppressing cell division and when they mutate,
they stop suppressing the cell cycle and it can
occur nonstop.
The End.