Download IBMitosis-Meiosis-student-notes

IB Biology Student Notes
N. Cunningham & J. Chen
Mitosis/Meiosis/Reproduction
You Say Mitosis and I Say Meiosis...
Or How Cells Reproduce
A. Introduction
1. What characteristic distinguishes living things from nonliving matter?
B. Cell division functions in reproduction, growth and repair
1. How does cell division play a role in the life of a unicellular organism?
2. How does cell division play a role in the life of a multicellular organism?
3. A dividing cell duplicates its DNA, distributes the two copies to opposite ends
of the cell, and then splits into two daughter cells.
Why must there be continuity in the duplication process of DNA each time cell
division occurs?
C. Cell division distributes identical sets of chromosomes to daughter cells
1. What is meant by the term "genome"?
a. Prokaryotic genome is …
b. Eukaryotic genome is made up of …
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2. DNA is packaged into chromosomes.
a. Every eukaryotic species has a characteristic ___________________
_________________________ in the nucleus.
b. Human somatic (body) cells have ________ chromosomes.
c. Human gametes (sex cells) have _________ chromosomes.
d. What is the structure of a eukaryotic chromosome?
e. What is chromatin?
f. What happens to chromatin after DNA duplicates?
g. Each duplicated chromosome consists of two
__________________ __________________ , which
contain identical copies of the chromosome's DNA.
h. What is a centromere?
i. As cell division occurs, what will eventually happen
to the sister chromatids?
3. What is meant by the term "cytokinesis"?
4. What is the point of Mitosis?
5. What is a clone?
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D. A Day in the Life of a Cell
1. Mitosis (M phase) alternates with the much longer Interphase in a cell's daily
life.
a. M phase ->
b. Interphase->
c. Interphase has three subphases:
G1 ->
S ->
G2->
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d. How is the cell cycle controlled
with checkpoints?
e. What happens to cells
in the G0 phase?
f. Explain the role of cyclins in the cell
cycle.
g. How could these cell cycle regulatory
proteins be used in cancer treatments?
E. Mitosis is a continuum of changes
1. What are the five subphases of mitosis?
2. What are cells doing by late
interphase and how do they appear? How do the
chromosomes appear?
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3. PROPHASE:
a. How do the chromosomes appear?
b. What begins to disappear?
c. As spindle fibers start to form,
where do they push the centrosomes
towards?
4. PROMETAPHASE:
a. What happens to the nuclear envelope?
b. Kinetochore microtubules?
5. METAPHASE:
a. Where do the chromatids line up?
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6. ANAPHASE:
a. What happens to the centromere?
b. What happens to the sister chromatids?
c. By late anaphase, what will you see at the
poles??
7. TELOPHASE:
a. What reappears?
b. Cytokinesis ->
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F. Cytokinesis divides the cytoplasm: a closer look
1. How does cytokinesis occur in animals?
2. How does cytokinesis occur in plants?
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G. Mitosis in eukaryotes may have evolved
from binary fission in bacteria.
1. How does binary fission in
prokaryotes occur?
2. What intermediate steps in evolution may have occurred between binary
fission and mitosis?
a. Dinoflagellates->replicated chromosomes are attached to
________________ _________________________________
b. Diatoms--> spindle develops ______________________________
______________________________________________________________
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H. Development and Differentiation
a. How does one cell (zygote) develop into a
multicellular organism using mitosis?
-.
-.
-.
b. Fate of germ layers
Ectoderm 
Mesoderm 
Endoderm 
c. What induces differentiation?
I. What is a STEM CELL and how can they be used in medicine?
1. What is a stem cell?
Stem cells have the potential to develop into many different kinds of cells in the body
during early life and growth. In addition, in many tissues stem cells serve as a sort of
internal repair system, dividing to replenish other cells as long as the person or animal is
still alive. When a stem cell divides, each new cell has the potential either to remain a
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stem cell or become another type of cell with a more specialized function, such as a
muscle cell, a red blood cell, or a brain cell.
2. Where do stem cells come from?
Embryonic vs. adult cells
Embryonic-Embryonic stem cells are
derived from embryos. Most
embryonic stem cells are derived from
embryos that develop from eggs that
have been fertilized in vitro
and then donated for research
purposes with informed consent of the
donors. They are not derived from eggs
fertilized in a woman's body.
Adult- An adult stem cell is thought to
be an undifferentiated cell, found
among differentiated cells in a tissue
or organ. The adult stem cell can
renew itself and can differentiate to yield some or all of the major specialized cell types
of the tissue or organ. The primary roles of adult stem cells in a living organism are to
maintain and repair the tissue in which they are found. Scientists also use the term
somatic stem cell instead of adult stem cell, where somatic refers to cells of the body
(not the germ cells, sperm or eggs). Unlike embryonic stem cells, which are defined by
their origin (cells from the preimplantation-stage embryo), the origin of adult stem cells
in some mature tissues is still under investigation.
3. Ethics of stem cell research
There are ethical issues involved in stem cell research, whether humans or other
animals are used. Use of embryonic stem cells involves the death of early-stage
embryos, but if therapeutic cloning is successfully developed the suffering of patients
with a wide variety of conditions could be reduced.
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J. How is cancer related to mitosis?
1. What is cancer?
2. What makes cancer cells different from normal cells?
4. What was the significance of HeLa cells?
5. How is a HeLa cell karyogram different from that of a normal human cell?
6. What is a mutagen and give some examples.
7. What is an oncogene?
8. What is a tumor-suppressor gene?
9. What is a tumor?
10.What is the difference between a benign and malignant tumor?
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11.How are cancer cells treated?
12. How do mutations in p53 site lead to cancer?
K. A close look at mitosis as a form of reproduction
1. Asexual reproduction relies on mitosis to pass along exact copies of its genes
to the offspring.(How many parents are needed for asexual reproduction? _____
a. Fission =
ex:
IN ANIMALS:
b. Budding =
ex:
c. Fragmentation/Regeneration =
ex:
d. Parthenogenesis =
IN PLANTS ASEXUAL REPRODUCTION IS CALLED VEGETATIVE PROPOGATION
1. Plants have the capacity for unlimited cell growth due to:
a. meristematic tissue
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2. Various methods of vegetative propagation have been developed to propagate
crop plants, orchards and ornamental plants.
a. cuttings –
4. What are the advantages of asexual reproduction?
a.
b.
c.
d.
5. Explain a disadvantage of asexual reproduction.
L. Meiosis is another type of cell reproduction used in sexually reproducing organisms
1. Types of cells made in meiosis?
2. Where does meiosis occur?
a. in animals->
b. in angiosperms (flowering plants) ->
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M. Why is meiosis necessary for organisms that reproduce sexually?
1. Meiosis maintains a constant number of chromosomes in a sexually
reproducing species from one generation to the next...HOW?
2. What would happen if sexually reproducing organisms used MITOSIS, not
MEIOSIS, to make their gametes?
N. Meiosis results in variation in the species
1. How does sexual reproduction ensure variation in the offspring?
2. Why is this important to evolution?
O. Background information and vocabulary needed for our understanding of meiosis.
1. Karyotype =
2. What is a karyogram and how can one be made?
3.
What is a somatic cell?
2. Number of chromosomes in a human somatic cell =
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4. Homologous chromosome pairs =
What is an allele? Example?
5. Karyograms can detect unusual chromosome # in a fetus.
Ex:
6. Sex chromosomes:
Females ->
Males ->
6. Autosomes =
7. Haploid (monoploid) Number (symbol=n)
8.Fertilization –
9. Zygote =
9. Diploid Number (symbol =2n)
So, what is the point of meiosis?????
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P. Meiosis reduces the chromosome number from diploid to haploid: a closer look.
1. What event precedes meiosis just as it did for mitosis?
2. Number of cell divisions in meiosis?
3. Number of possible cells (gametes) formed from meiosis?
4. Chromosome number of cells produced by meiotic divisions?
5. Meiosis reduces the chromosome number in half by copying the chromosomes
_____ but dividing _________.
a. What happens in Meiosis I?
Are the resulting cells haploid or diploid?_______
b. What happens in Meiosis II?
6. PHASES
a. INTERPHASE- What happens
in the "S" phase of interphase
just prior to meiosis?
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b. PROPHASE I
* What happens to the homologous pairs of
chromosomes?
* CROSSING OVER CAN OCCUR HERE!!! What is that????
Key words here are:
Tetrad =
Synapsis =
Chiasmata =
c. METAPHASE I
*Key event?
d. ANAPHASE I
* Key event?
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e. TELOPHASE I
* What does each
newly formed cell contain?
f. INTERKINESIS
*What is it?
* What doesn't happen here
that did happen in interphase?
g PROPHASE II
*What happens?
*Does crossing over occur again?
h. METAPHASE II
* What structures are lined up at the metaphase
plate?
i. ANAPHASE II
*What separates?
(How is this different from
anaphase I?)
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j. TELOPHASE II
*Key events?
1.
2.
3.
k. What is finally formed at the end
of MEIOSIS?
Q. Key differences between Meiosis and Mitosis
Mitosis
Chromosome number
at the end of the cell
division
Genetic resemblance to
parent cell?
# Cell Divisions?
(PMAT)
# cells produced at the
end
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Meiosis
1. In meiosis I, there are three events that occur which do not happen in mitosis...
a. During prophase I ->
b. In metaphase I -->
c. In anaphase I -->
2. How does Meiosis II compare to the events in mitosis?
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R. Sexual Life Cycles
Produce Genetic
Variation Among
Offspring
Three mechanisms
contribute to genetic
variation:
1. Independent
Assortment ->
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The number of combinations of gametes possible when chromosomes assort
independently = _______
where n is the number of homologous pairs
In fruit flies, the diploid # =8. How many possible different gametes can result?
What is the possible number of different gametes that can be produced in one human
individual?
2. Another mechanism for variation is due to crossing over during prophase I.
Why does this create more
possible variations in
the gametes?
3.A third mechanism for variation is due
to the random nature of fertilization.
What does this mean?
4. What is the role of mutations in the
concept of variation?
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S. How does variation tie into the concept of Darwin's theory of natural
selection/evolution?
T. Formation of Sperm and Eggs in humans
1. Spermatogenesis
(meiosis in males)
* Facts about sperm:
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2. Oogenesis (meiosis in females)
Spermatogenesis
Oogenesis
Numbers of gametes
produced in a lifetime?
Number of living
gametes produced by
the end of meiosis?
Size of gamete(s)
made?
Timing?
U. What happens when meiosis makes a mistake?
-.
Consequence:
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Nondisjuction can cause:
- .
-.
-.
Effect of age of parent on incidence of Down Syndrome?
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