Transcript CP Biology Cell Cycle

Cell Cycle
**The cell cycle or the cell division cycle is a
series of events that take place when a cell
is going to divide and reproduce a new cell.
This process must take place when:
1. A fertilized egg develops into a multicellular
organism
2. An organism must replace cells that have
been injured or destroyed
3. An organism grows
There are 2 main parts to this cycle:
1. Interphase
2. Mitotic phase (M phase)
 SCI.9-12.B-2 - [Standard] - The student
will demonstrate an understanding of the
structure and function of cells and their
organelles.
SCI.9-12.B-2.6 - [Indicator] - Summarize
the characteristics of the cell cycle:
interphase (called G1, S, G2); the phases
of mitosis (called prophase, metaphase,
anaphase, and telophase); and plant and
animal cytokinesis.
Chromosomes
*
 Homologous chromosomes –
Chromosomes that have the same type
of gene located at the same spot (locus).
You inherit one from your mom and one
from your dad. They both give you a
number one chromosome but dad’s
might have a gene for brown eyes and
mom’s a gene for green eyes. Alleles –
different forms of same gene
*
Humans have 23 pair of chromosomes.
22 pair of autosomes determine
characteristics
The 23rd pair determines the sex of the
child
XX = female
XY = male
*
Genes that are found on the same
chromosome are said to be linked and
are inherited together. For example, red
hair and freckles are on the same
chromosome and are usually inherited
together.
Structure of a chromosome
Chromatids are connected by the centromere and have a LONG AND SHORT ARM.
 *Chromatids are
connected by the
centromere and
have a LONG AND
SHORT ARM.
chromatid
p = short arm
q = long arm
The ends of the arms
are called telomeres. the
entireia a
Involved in aging
p arm
q arm
telomere
*
 Centromeres and telomeres are made of
short sections of DNA repeated over and
over.
For example, AAATTT AAATTT
AAATTT AAATTT.
*INTERPHASE
Interphase is when the cell is obtaining
nutrients, growing, and making new
cellular parts. Inter phase is sometimes
called the “resting stage” but it does not
rest here. Interphase has 3 parts:
G1 – Growth 1
S phase -- when DNA copies itself
G2 – Growth 2 the cell is getting ready
to divide
Plant cell in interphase
SCI.9-12.B-2.6 - [Indicator] - Summarize
the characteristics of the cell cycle:
interphase (called G1, S, G2); the phases
of mitosis (called prophase, metaphase,
anaphase, and telophase); and plant and
animal cytokinesis.
*Prophase
 Second stage of cell cycle – the first in
the M phase
 Everything that appears in this phases
will disappear in telophase. Everything
that disappeared here will re-appear in
telophase
*Prophase
continued
1. Chromatin condenses (shortens) into
chromosomes
2. Centrioles start moving toward poles
(ends of cell).
3. Mitotic spindle begins to form.
4. The nucleolus disappears.
5. The nuclear membrane disappears.
6. Mitotic spindle is fully formed with
chromosomes attached to its fibers. And
the chromosomes are all moving toward
the center of the cell (called equator).
*Metaphase
In metaphase, all the chromosomes have
their centromeres lined up on the
equator.
SCI.9-12.B-2.6 - [Indicator] - Summarize
the characteristics of the cell cycle:
interphase (called G1, S, G2); the phases
of mitosis (called prophase, metaphase,
anaphase, and telophase); and plant and
animal cytokinesis.
Plant cell in metaphase
*Anaphase
In anaphase, the centromere divides and
separates the two chromtids. They are
now called chromosomes and they move
away from the equator toward the poles.
(Think A = Away A = anaphase)
Plant Cell in Anaphase
SCI.9-12.B-2.6 - [Indicator] - Summarize
the characteristics of the cell cycle:
interphase (called G1, S, G2); the phases
of mitosis (called prophase, metaphase,
anaphase, and telophase); and plant and
animal cytokinesis.
*Telophase
Telophase is the last stage of mitosis and it
is the opposite of prophase. Whatever
appeared in prophase, will disappear in
telophase and whatever disappeard in
prophase will reappear in telophase.
1. Chromosomes go back to chromatin.
2. Mitotic spindle disappears.
3. Nucleolus reforms.
4. Nuclear membrane reforms
Plant Cell in telophase
*Cytokinesis
After the nucleus finishes dividing, the
cytoplasm has to divide. It divides evenly
down the middle so that the 2 new cells
are the same size.
In plant cells, the cell wall begins to form
first. Then the cell membrane divides.
Cytokinesis in plant cells
*How long does it take for
cells to divide?
The more complicated a cell is the longer
it takes to divide. Your skin cells take
about 10 hours to divide. Some cells in
your body do not divide at all. For
example, your brain cells are in the G0
phase, meaning they do not divide. Your
muscles will not divide again unless they
are damaged in some way.
SCI.9-12.B-2.6 - [Indicator] - Summarize
the characteristics of the cell cycle:
interphase (called G1, S, G2); the phases
of mitosis (called prophase, metaphase,
anaphase, and telophase); and plant and
animal cytokinesis.
Cells Undergoing Mitosis
Interphase
Metaphase
Telophase
Prophase
Anaphase