Download Cell Growth & Division

Cell Growth & Division:
Mitosis
Cell Growth and Division
I. Chemical Pathways
A. Limits to Cell Growth (two main reasons why
cells divide)
1. DNA “Overload”
a. The larger the cell
gets, the bigger the
demand on its DNA (DNA
found in the nucleus of
the cell)
b. Creates “information
crisis” (too much Cell,
too little DNA!)
2. Exchanging Materials
a. Rate of exchange of materials (food,
water, wastes) depends on the surface area
of the cell)
b. Rate at which food and oxygen are used
up depends on cell’s volume
c. Ratio of
surface area to
volume- when cell
grows, volume
increases faster
than it’s surface
area.
3. Cell Division- to solve the problem of small
surface area to volume, a cell divides into two
daughter cells
a. Cell replicates (copies) it’s DNA before
division
b. Rates vary from 30 minutes (bacteria) to
many decades
Concept 9.1 - All cells come from
cells
• The division of cells into more cells enables
living things to repair damage, to grow and
to produce offspring
Cell Repair & Growth
• Enables your
body to
produce new
cells to
replace dead
cells
Reproduction
• Asexual
– Single cell duplicates its genetic material and
splits into 2 genetically IDENTICAL cells
• Sexual
– Genetic material from each of 2 parents
combine, producing offspring that differ
genetically from either parent
Asexual Reproduction
• Asexual reproduction
is the formation of
offspring from one
parent
• Offspring produced by
asexual reproduction
are genetically
identical to the parent
Binary fission is
the process of
cell division in
prokaryotes
Concept 9.2 – The cell cycle multiplies
cells
• At this moment,
millions of cells in
your body are dividing,
each forming 2 new
cells.
Chromosomes
• Almost all of the genes of a eukaryotic cell are
located in the nucleus.
• Most of the time, this genetic material exists in
long fibers too thin to be seen under a light
microscope.
• As a cell prepares to divide – these fibers
condense and become visible as chromosomes.
Chromosomes
• Chromosomes are tightly coiled DNA
molecules and associated proteins
• In eukaryotes,
histone proteins
help maintain the
compact structure
of chromosomes
DNA
Histone
• In dividing cells,
chromosomes
are composed of
2 identical
chromatids
constricted
together at a
centromere
• Chromosomes
are categorized
as either sex
chromosomes or
autosomes
Sex
Chromosomes
• Homologous chromosomes consist of one
autosomal chromosome from each parent
II. Cell Division
A. Chromosomes- genetic information carried on
chromosomes
1. Before cell division each
chromosome is replicated
(copied)
2. Each chromosome
consists of two identical
“sister” chromatids
3. Each pair of
chromosomes attached to
area called centromere
Cell Cycle
• The cell
cycle goes
from the
“birth” of a
cell until it
reproduces
itself.
Cell Cycle
• Interphase (**The resting phase)
– 90% of the cell cycle is spent here
– Stage where the cell performs its functions
• Increasing proteins, releasing enzymes, etc
– G1, S, and G2 stages
• G1 – Gap 1 = Cell growth and activity
• S – DNA Synthesis = Genetic material (DNA)
copied
• G2 – Gap 2 = Cell prepares to divide; organelles
produced (double in #)
Cell Cycle
• Mitotic Phase
– Contains 2 processes
• Mitosis
– Nucleus and duplicated chromosomes divide and
are evenly distributed, forming 2 “daughter”
nuclei
• Cytokinesis
– Cytoplasm is divided into 2
Cell Cycle
• The cell cycle is
the repeating of
events that make
up the life of a cell
• The cell cycle
consists of cell
division and
interphase
Cell Division
Concept 9.3
Cells divide during the mitotic phase
Interphase
• Interphase consists of a phase of growth
(G1), a phase of DNA replication (S), and a
phase of preparation for cell division (G2)
Mitotic Phase
• Mitosis is divided into: prophase,
metaphase, anaphase, and telophase
• ACRONYM: P M A T
• Mitosis results in two offspring cells that
are genetically identical to the original cell
C. Mitosis- Division of Cell Nucleus and
Cytokinesis. Divided into 4 phases
1. Prophase- First and longest phase.
• Chromosomes become visible
• Centrioles separate and migrate to
opposite sides of nucleus
•Chromosomes
attach to spindle
fibers.
•Nuclear membrane
breaks down
2. Metaphase- Chromosomes line up across
the center of the cell
3. Anaphase•Centromeres that join chromatids separate.
•Sister chromatids separate
•Chromosomes moves to opposite poles
4. Telophase•Condensed chromosome begin to disperse
•Nuclear envelope re-forms around cluster of
chromosomes
•Nucleolus becomes visible
D. Cytokinesis- division of cytoplasm following
mitosis
1. Animal cells- cell
membrane drawn inward until
cytoplasm is pinched into two
nearly equal parts
2. Plant cells- cell plate
forms midway between
divided nuclei. Gradually
develops into separating
membrane. Eventually cell
wall begins to appear.
Cytokinesis
• The process by which the
cytoplasm divides and one
cell becomes two
individual cells
• Animals - cell pinches
inward
• Plants - a new cell wall
forms between the two
new cells
Mitosis Summary
Concept 9.4 – Cancer cells grow and
divide out of control.
• Timing during normal cell division is
critical to normal growth and development.
• When the “control system” malfunctions,
cells may reproduce at the wrong time or in
the wrong place.
III. Regulating the Cell Cycle
A. Controls on Cell Division
1. Protein called cyclin regulates the timing of
the cell cycle in eukaryotic cells
2. Cells will grow in petri dish until they come
into contact with other cells. Cell growth turned
“on” and “off”
3. Two main types of regulatory proteins
a. Internal regulator- respond to events
inside the cell. (e.g. Cell will not enter
mitosis until all chromosomes replicated.
b. External regulatorrespond to events outside
the cell. (e.g. Wound
healing and embryonic
development.) can also
prevent excessive cell
growth
B. Uncontrolled Cell Growth
1. Cancer- do not
respond to signals that
regulate growth of most
cells. Form masses
called tumors
2. Don’t respond to
external growth
regulators. Some may
be genetic.
Tumors & Cancer
• Benign tumors
– Abnormal mass of essentially normal cells
– Depending on their location they sometimes cause health
problems
– Often removed via surgery
• Malignant tumors
– Masses of cells that result from reproducing cancer cells
– Cancer disrupts the timing of cell division – this disruption
leads to uncontrolled cell division
• Metastasis
– Spread of cancer beyond its original site
Spread of cancer cells
in breast cancer
Metastasis
Cancer Treatment
• When possible, malignant tumors are removed with
surgery
• To treat cancer on the cellular level – radiation and
chemotherapy is often used
– Radiation exposes the cells to high energy radiation,
which disrupts cells division
– Chemotherapy involves treating patients with cytotoxic
chemicals which prevent cell division
• Different types of chemotherapy drugs affect cell division in
different ways (preventing the spindle fibers from forming,
“freezing” the spindle, etc)
Cancer Treatment
• Radiation & Chemotherapy often causes
undesirable side effects in normal body cells that
rapidly divide
– Radiation can affect ovaries & testes – and can cause
sterility
– Chemotherapy often damages intestinal cells or hair
follicles (fast growing cells), causing nausea or hair
loss
Cell Growth & Division:
Meiosis
Concept 9.5 – Meiosis functions in
sexual reproduction.
• Only dogs produce more dogs, only trees produce
more trees, and only people produce more people.
– BUT: “Like begets similar to, but not exactly like.”
Sexual Reproduction
• Sexual reproduction is
the formation of
offspring through the
union of a sperm and
an egg
• Offspring produced by
sexual reproduction
are genetically
different from the
parents
I. Meiosis
A. Chromosome number
1. Diploid number- means “two sets”.
Represented by symbol 2N. One of each set
from mother/father. Sets called homologous
chromosomes
a. Diploid cells found in body
cells; Human cells = 46
chromosomes
b. Contains two sets of
chromosomes and two sets of
genes
2. Haploid number- means “one set”.
Represented by N.
a. Gametes all haploid; Human sex cells =
23 chromosomes
b. Haploid cells (gametes) produced by
meiosis
• Diploid (2n) is the
number of
chromosomes in
cells that have
homologous pairs of
autosomes and 2
sex chromosomes
Meiosis
• Meiosis produces haploid daughter cells from
specialized cells in diploid organisms.
• Despite the similarity in their names, meiosis is
different from mitosis in two major ways.
– The first major difference is that meiosis produces four
new offspring cells, each with one set of
chromosomes—thus half the number of chromosomes as
the parent cell.
– The second major difference is that meiosis involves the
exchange of genetic material between homologous
chromosomes.
Meiosis
• Goes through
two divisions
– Meiosis 1
– Meiosis 2
• During
meiosis,
a cell
divides
twice
B. Phases of Meiosis (2 stages)
1. Meiosis I- each chromosome is
replicated (copied)
a. Similar to mitosis- but chromosomes
line up in pairs- Tetrads in prophase I
b. Exchange of portions of chromatids
takes place while chromosomes exist as
tetrads. Called crossing-over
c. Results in two diploid daughter cells
1.
Meiosis IIa. No new replication of
chromosomes
b. Results in four
haploid daughter cells
C. Gamete formation- in
animals: egg and sperm
• Spermatogenesis is
the process by
which sperm cells
are produced
• Oogenesis is the process that produces egg
cells (ova)
Meiosis and fertilization
It’s easy to see how genes located on different
chromosomes assort independently, but what
about genes located on the same
chromosomes? Wouldn’t they generally be
inherited together?
The answer to these questions, Thomas
Hunt Morgan first realized in 1910, is yes!
D. Linkage and Gene Maps
1. Gene Linkage- genes on same
chromosome almost always inherited together
(unless separated by “crossing over” during
meiosis)
a. Experiments by Thomas Hunt Morgan
(1910)- research on fruit flies (Drosophila
melanogaster)
1). Chromosomes big, only 4 pair,
bred quickly
2). Concluded: chromosomes
assort independently, not the
individual genes
b. By luck, 6 of the 7 genes Mendel studied
were on different chromosomes (the two genes
found on the same chromosome were so far
apart that they also assorted independentlydue to crossing over)
2. Gene Maps- rate of “crossing over” used to
map location of genes on chromosomes
a. Alfred Sturtevant- said further apart the
genes were, the more likely they were to be
separated during crossover in meiosis
b. Gathered data and “mapped” location of
genes in Drosophila chromosomes
c. Also used to map human genome
Chapter 9
Cell Growth & Division
As a cell becomes larger, its
a.
volume increases faster than its surface
area.
b.
surface area increases faster than its
volume.
c.
volume increases, but its surface area
stays the same.
d.
surface area stays the same, but its
volume increases.
As a cell becomes larger, its
a.
volume increases faster than its
surface area.
b.
surface area increases faster than its
volume.
c.
volume increases, but its surface area
stays the same.
d.
surface area stays the same, but its
volume increases.
As a cell grows, it
a.
places more demands on its DNA.
b.
uses up food and oxygen more quickly.
c.
has more trouble moving enough materials
across its cell membrane.
d.
all of the above
As a cell grows, it
a.
places more demands on its DNA.
b.
uses up food and oxygen more quickly.
c.
has more trouble moving enough materials
across its cell membrane.
d.
all of the above
If the length of a cell increases 10 times, its
volume increases about
a.
5 times.
b.
10 times.
c.
100 times.
d.
1000 times.
If the length of a cell increases 10 times, its
volume increases about
a.
5 times.
b.
10 times.
c.
100 times.
d.
1000 times.
The speed with which wastes are
produced by a cell depends on the cell's
a.
ratio of surface area to volume.
b.
environment.
c.
volume.
d.
surface area.
The speed with which wastes are
produced by a cell depends on the cell's
a.
ratio of surface area to volume.
b.
environment.
c.
volume.
d.
surface area.
Unlike small cells, large cells have more
trouble
a.
dividing.
b.
producing daughter cells.
c.
moving needed materials in and
waste products out.
d.
making copies of their DNA.
Unlike small cells, large cells have more
trouble
a.
dividing.
b.
producing daughter cells.
c.
moving needed materials in and
waste products out.
d.
making copies of their DNA.
When during the cell cycle are chromosomes
visible?
a.
only during interphase
b.
only when they are being replicated
c.
only during cell division
d.
only during the G1 phase
When during the cell cycle are chromosomes
visible?
a.
only during interphase
b.
only when they are being replicated
c.
only during cell division
d.
only during the G1 phase
When during the cell cycle is a cell's DNA
replicated?
a.
G1 phase
b.
G2 phase
c.
S phase
d.
M phase
When during the cell cycle is a cell's DNA
replicated?
a.
G1 phase
b.
G2 phase
c.
S phase
d.
M phase
Which event occurs during interphase?
a.
The cell grows.
b.
Centrioles appear.
c.
Spindle fibers begin to form.
d.
Centromeres divide.
Which event occurs during interphase?
a.
The cell grows.
b.
Centrioles appear.
c.
Spindle fibers begin to form.
d.
Centromeres divide.
Cell division is represented in Figure 10-1 by
the letter
a.
A.
b.
B.
c.
C.
d.
D.
Cell division is represented in Figure 10-1 by
the letter
a.
A.
b.
B.
c.
C.
d.
D.
The cell cycle is the
a.
series of events that cells go through as
they grow and divide.
b.
period of time between the birth and the
death of a cell.
c.
time from prophase until cytokinesis.
d.
time it takes for one cell to undergo
mitosis.
The cell cycle is the
a.
series of events that cells go
through as they grow and divide.
b.
period of time between the birth and the
death of a cell.
c.
time from prophase until cytokinesis.
d.
time it takes for one cell to undergo
mitosis.
The structure labeled A in Figure above is called
the _____________.
a.
centromere.
b.
centriole.
c.
sister chromatid.
d.
spindle.
The structure labeled A in Figure above is called
the _____________.
a.
centromere.
b.
centriole.
c.
sister chromatid.
d.
spindle.
The structures labeled B in Figure above are
called
a.
centromeres.
b.
centrioles.
c.
sister chromatids.
d.
spindles.
The structures labeled B in Figure above are
called
a.
centromeres.
b.
centrioles.
c.
sister chromatids.
d.
spindles.
The first phase of mitosis is called
a.
prophase.
b.
anaphase.
c.
metaphase.
d.
interphase.
The first phase of mitosis is called
a.
prophase.
b.
anaphase.
c.
metaphase.
d.
interphase.
During which phase of mitosis do the
chromosomes line up along the middle of the
dividing cell?
a.
prophase
b.
telophase
c.
metaphase
d.
anaphase
During which phase of mitosis do the
chromosomes line up along the middle of the
dividing cell?
a.
prophase
b.
telophase
c.
metaphase
d.
anaphase
Which of the following represents the phases of
mitosis in their proper sequence?
a.
prophase, metaphase, anaphase, telophase
b.
interphase, prophase, metaphase,
anaphase, telophase
c.
interphase, prophase, metaphase,
telophase
d.
prophase, metaphase, anaphase,
telophase, cytokinesis
Which of the following represents the phases of
mitosis in their proper sequence?
a.
prophase, metaphase, anaphase,
telophase
b.
interphase, prophase, metaphase,
anaphase, telophase
c.
interphase, prophase, metaphase,
telophase
d.
prophase, metaphase, anaphase,
telophase, cytokinesis
What is the role of the spindle during
mitosis?
a.
It helps separate the chromosomes.
b.
It breaks down the nuclear membrane.
c.
It duplicates the DNA.
d.
It divides the cell in half.
What is the role of the spindle during
mitosis?
a.
It helps separate the chromosomes.
b.
It breaks down the nuclear membrane.
c.
It duplicates the DNA.
d.
It divides the cell in half.
One difference between cell division in plant
cells and in animal cells is that plant cells
have
a.
centrioles.
b.
centromeres.
c.
a cell plate.
d.
chromatin.
One difference between cell division in plant
cells and in animal cells is that plant cells
have
a.
centrioles.
b.
centromeres.
c.
a cell plate.
d.
chromatin.
During normal mitotic cell division, a parent cell
having four chromosomes will produce two
daughter cells, each containing
a.
two chromosomes.
b.
four chromosomes.
c.
eight chromosomes.
d.
sixteen chromosomes.
During normal mitotic cell division, a parent cell
having four chromosomes will produce two
daughter cells, each containing
a.
two chromosomes.
b.
four chromosomes.
c.
eight chromosomes.
d.
sixteen chromosomes.
Cancer is a disorder in which some cells
have lost the ability to control their
a.
size.
b.
spindle fibers.
c.
growth rate.
d.
surface area.
Cancer is a disorder in which some cells
have lost the ability to control their
a.
size.
b.
spindle fibers.
c.
growth rate.
d.
surface area.
Cancer cells form masses of cells called
a.
tumors.
b.
cyclins.
c.
growth factors.
d.
p53.
Cancer cells form masses of cells called
a.
tumors.
b.
cyclins.
c.
growth factors.
d.
p53.
Meiosis of a cell containing 50
chromosomes would result in
a.
2 sperm cells with 50 chromosomes
b.
2 egg cells with 25 chromosomes/ea.
c.
4 sperm cells with 25 chromosomes
d.
None of the above
Meiosis of a cell containing 50
chromosomes would result in
a.
2 sperm cells with 50 chromosomes
b.
2 egg cells with 25 chromosomes
c.
4 sperm cells with 25
chromosomes
d.
None of the above
(a)
(b)
(d)
(c)
(f)
(e)
(g)
(h)
(i)
What is the name of structure (f)?
Centrioles
(j)
(a)
(b)
(d)
(c)
(f)
(e)
(g)
(i)
(h)
(j)
What phase is represented by letter (a)?
Interphase
(a)
(b)
(d)
(c)
(f)
(e)
(g)
(i)
(h)
(j)
What phase is represented by letter (j)?
anaphase
(a)
(b)
(d)
(c)
(f)
(e)
(g)
(h)
(i)
What are structures (c) called?
Spindle fibers
(j)
(a)
(b)
(d)
(c)
(f)
(e)
(g)
(i)
(h)
(j)
What phase is represented by letter (d)
metaphase
(a)
(b)
(d)
(c)
(f)
(e)
(g)
(i)
(h)
(j)
What phase is represented by letter (g)
telophase
(a)
(b)
(d)
(c)
(f)
(e)
(g)
(i)
(h)
(j)
What phase is represented by letter (b)?
Prophase