Transcript The Cell Cycle

The Nucleus
Asexual Reproduction:
Mitosis
&
Cell Division
General Info:
Nucleus:
–the “brain” of the cell
–controls the cells activities
–responsible for cell division,
protein synthesis
General Info Cont.
Nucleus:
–contains genetic material called
DNA
–DNA long chain (chromatin) of
genetic information (eukaryotes)
–In prokaryotes (bacteria) DNA is in
the shape of a ring called a
plasmid
Nucleus
Nucleolus
Chromatin
Chromosomes:
–made of Deoxyribonucleic Acid 
DNA wrapped around proteins
–Chromosomes in eukaryotes are
“rod shaped” structures made of
DNA and proteins
Chromosomes:
• consist of 2 halves called
chromatids
• “sister chromatids” are
connected in the center by a
centromere
Chromosome
(Coiled chromatin)
Ck question
Topic: DNA and Chromosomes
Date: 1-4-2010
1.
2.
3.
4.
Genetic material of a cell is called …
The location of #1
The ring of DNA found in Bacteria is…
Chromosomes consist of 2 halves
known as…
Chromosome Numbers:
• Each species has a characteristic
number of chromosomes in each cell.
• ex. Fruit flies (drosophila) = 8
chromosomes
• horse has 64 chromosomes
• humans have 46 and chimpanzees
have 48 chromosomes
From 7 characteristics of living things:
All living things  Grow
• Growth occurs from the division of
cells.
• Cell Division (cellular reproduction)
allows cells to:
1. Grow in size
2. Grow in number
3. Replace worn out, injured or dying
cells
2 Forms of Cellular Reproduction
(cell division):
1. Asexual Reproduction 
involves only one parent cell
a. Occurs in Autosomes or
somatic cells … body cells
b. Plants/animals
2 Forms of Cellular Reproduction
(cell division) Cont…
c. protists (protozoan) =
single celled organisms
(binary fission)
d. fungi
e. bacteria = binary fission
2 Forms of Cellular Reproduction
(cell division):
2.Sexual Reproduction
involves 2 parents cells
a. Gametes = sex cells
b. Making gametes!!!
Sexual reproduction:
Occurs in sperm cells and egg cells
The Cell Cycle
Asexual Reproduction aka MITOSIS
The Cell Cycle is responsible
for:
– birth and death of a cell
– Cell division of nucleus, home of
hereditary
information…chromosomes
– Cell division (Cell Cycle) consists
in 3 processes
Cell Cycle consists in 3
processes
1. Interphase
2. Division of the nucleus=
mitosis
3. Division of the cytoplasm =
cytokinesis
Ck question
Topic: Cell reproduction
Date: 1-4-2010
1. How many chromosomes does a
normal humans have?
2. Identify 3 reasons cells divide.
3. The 2 types of cellular reproduction
are…
4. Define gametes.
5. Define autosome.
Before a cell divides….
Interphase
(nucleus)
• Cell spends
most time
here
Interphase:
• Divided into 3 phases
1. G1 – cells grow to mature size
2. S – DNA is copied or duplicated
called DNA replication
1. G2 – cell prepares to divide
• Some cells have a G0 phase,
they do not replicate after
maturity. Ex. Nervous System
Mitosis:
One cell (PARENT CELL) divides into
2 identical cells (Daughters)
–
–
1.
2.
3.
4.
divisions: nucleus divides
a series of chronological steps:
prophase
Division
of
the
metaphase
nucleus
(DNA)!!
anaphase
telophase
Mitosis
Prophase:
• Chromatin condenses, becomes
visible strands of DNA called
chromosomes
• 2 chromosomes are made of “sister
chromatids”
• chromatids are connected by
centromere
• centrioles in animal cells begin to
separate (opposite ends or poles)
Prophase Cont.
• spindle fibers form (football
shape) from the centrioles and
connect to centromere of each
chromatid
• nuclear membrane fades
• chromatids (chromosomes)
begin moving to center
Spindle
fibers
Chromosomes
Centrioles
Centromere
Metaphase: (middle)
• chromosomes (chromatids) line
up in the middle of the cell
• centromere divide
• chromosomes are pulled apart
separate chromosomes (???)
Spindle fibers
Chromosome
Centromere
Anaphase: (away)
• centromere divides
• chromatids separate
• move to opposite ends of cell
• complete set of chromatids go
to each pole
chromatid
Telophase:
• final step of mitosis
• chromatids unwind, spindle
fibers disappear
• nuclear membrane forms
around each of chromatids
Cytokinesis:
• final step in the cell cycle
• cytoplasm (and organelles) divide
equally in cells
• animals-pinching in of the cell
membrane forming a cleavage
furrow
• plants - cell plate forms across the
middle growing outward
In animal cells
• (begins outside the cell)
In plate cells
• (begins inside the cell)
Results of Mitosis:
• division of the nucleus (Asex. Reprod.)
• products are 2 new cells with identical
information
to each other and to the parent cell
• most cells reproduce asexually  mitosis
– ex. Of cells produced through mitosis
include:
in animals: blood cells, skin cells,
cheek cells,
in plants: root cells, stem cells, leaves
Parent Cell
Identical
Daughter Cells
Identical Daughter Cells
Two identical
daughter
cells
Parent Cell
• mitosis