Advantages and disadvantages to asexual and sexual reproduction as a strategy
Different methods of asexual reproduction
Different methods of sexual reproduction
What is the difference between mitosis and meiosis?
How are mitosis and meiosis similar?
Can you describe Interphase, Mitosis, and Cytokenesis in 10 seconds each? What about 5 seconds each? What about 2?
Don't forget about the final exam on Thursday!
Here is the homework due Wednesday:
Pg 215 # 1 - 5
Pg 223 # 1 - 9
Pg. 233 # 1, 2, 4, 8, 10, 12-16.
These are the answers to last day's assignments:
Pg 184 # 1-26
1. Cell division is necessary in unicellular organisms
so that these organisms can reproduce
themselves in great numbers.
2. Cell division is necessary in multicellular
organisms for growth and to replace worn-out
cells.
3. The three stages of the cell cycle are interphase,
mitosis, and cytokinesis.
4. Cells are performing the life functions of a cell
during interphase. Digestive system cells will
be making enzymes, retina cells will be performing
chemical reactions so that you are
able to see. In addition, the cell is preparing
for cell division by duplicating organelles.
5. The checkpoint proteins check for the following:
(a) Are there enough nutrients in the cell
to support growth? (b) Is the DNA damaged?
(c) Has the DNA replicated? (d) Have the
chromosomes become attached to the spindle
fibres? (e) Have the chromosomes moved to
the poles in anaphase?
6. If the cell as unable to make the proteins to
form spindle fibres, mitosis could not occur
successfully since the chromosomes would not
be able to attach. The result would be that the
chromosomes would not be equally distributed
between cells.
7. If there is a mutation in a checkpoint protein,
the cell may continue to proceed through the
cell cycle and the result is that the cell may die
or have a mutation.
8. Bacteria grow at an exponential rate through
binary fission and mutations do occur. If a
mutation occurs that allows the bacteria to
become resistant to antibiotics, these bacteria
will survive and multiply.
9. The chart should include the following:
Interphase: Cell carries out the functions necessary
for survival, and if the cell is going to
divide it will prepare for cell division by copying
the DNA and duplicating organelles.
Mitosis: The duplicated chromosomes are
divided into two equal parts.
Cytokinesis: The two nuclei and the contents
of the cell separate into two daughter cells.
10. The chart should include the following:
Prophase: The chromosomes become visible,
and the spindle fibres appear and chromosomes
attach.
Metaphase: The spindle fibres pull the Xshaped
chromosomes into a single line at the
equator.
Anaphase: The spindle fibres contract and
shorten, and the chromatids are pulled to
opposite poles of the cell.
Telophase: The spindle fibres disappear, and
the nuclear membrane forms around each set
of chromosomes.
11. The daughter plant cells will remain together
with a cell plate between them, which will
form the cell membrane and cell wall. The
animal cells will pinch completely apart.
12. The major disadvantage of asexual reproduction
is that there is very little variation so all
the offspring are identical. If conditions
change, all of the individuals could die.
13. Three reasons for human-assisted cloning are
to save an endangered species, to mass produce
an organism with a desired trait, or to
correct health problems.
14. Reproductive cloning is also known as adult
DNA cloning, and it is used to duplicate an
entire individual that has a desired trait.
15. Stem cells are cells that are not yet differentiated
to become a specific kind of cell. They
have the potential to become many different
types of cells.
16. Two characteristics of asexual reproduction are
that only one parent is required and all of the
offspring are genetic clones of the parent.
17. The nuclear membrane must disintegrate during
prophase so that the chromosomes are free
to attach to the spindle fibres.
18. (a) These cells are plant cells.
(b) You know that they are plant cells because
there appears to be a cell wall, there is no
centromere for the spindle fibres to attach
to, and the cells remain side by side after
cell division.
(c) The correct sequence is C, A, D, B.
(d) Diagram C shows prophase where the
chromosomes become visible. Diagram A
show metaphase where the chromosomes
are lined up in single file at the equator.
Diagram D shows anaphase where the
chromatids move to opposite poles.
Diagram B shows telophase where the
nuclear membrane forms around the sets
of chromosomes.
19. If the chromosomes do not separate out correctly
during anaphase, the cell will probably
not pass the checkpoints to go through the
rest of the cell cycle. The cell will die, or it
may go unchecked so that one daughter cell
will end up with more chromosomes than the
other daughter cell.
20. Cancer cells spread to a new location when
they break away and move into the bloodstream,
where they may begin to divide and
form a new tumour.
21. The blood vessels branch into the tumour and
deliver nutrients to it, which allows it to grow
even more rapidly.
22. A laboratory technician can identify cancer
cells because these cells have a large abnormal
nucleus since there are extra chromosomes
inside.
23. Only less complex forms of life can reproduce
asexually because lower forms have only a few
types of cells. Higher forms have many types
of specialized cells to form complex tissues.
24. There are concerns about stem cell research
because some people feel it is wrong to
destroy cells that are able to develop into an
individual.
25. To determine the best conditions for reproduction
of an amoeba, the scientist might put
the amoeba in different environments such as
more light, less light, warmer temperatures,
colder temperatures, more acidic, or less
acidic. The conditions that produced the
fastest rate of growth without any mutations
would be the ideal conditions.
p. 194
1. Genetic diversity is the inherited differences in
a population. For example, not everyone in the
classroom is the same height.
2. The function of meiosis is to reduce the chromosome
number so that when the egg and
sperm unite the original number of chromosomes
will not be doubled.
3. (a) The haploid number of chromosomes in
humans is 23.
(b) The diploid number of chromosomes in
humans is 46.
4. Another name for a fertilized egg is a zygote.
5. Homologous chromosomes are a matching
pair of chromosomes that are the same size
and shape. They have genes coding for the
same trait in the same location. (One member
of the pair originally came from the mother’s
egg and the other from the father’s sperm).
Pg 203
1. The number of chromosomes in a human skin
cell is 46 (the diploid number) and in a human
egg cell is 23 (the haploid number).
2. To identify a pair of homologous chromosomes,
you would look for two chromosomes
that have the same size and shape.
3. The benefits of genetic diversity are that
organisms may have new characteristics that
allow them to be better equipped to cope with
changes in the environment. The organism
may gain an advantage over another organism.
4. For a zygote to become an embryo, the cell
must undergo mitosis and cell division.
5. (a) Meiosis II
(b) Meiosis I
(c) Meiosis I
(d) Meiosis I
(e) Meiosis II
6. Cannot be uploaded at this time. Mr. Gill is working on a solution.
7. In meiosis I, the homologous chromosomes
are paired at the equator. In mitosis, the
homologous chromosomes are unpaired and
line up individually at the equator.
8. There is the diploid number (46 chromosomes
in humans) in metaphase of mitosis and the
haploid number (23 chromosomes or 46 chromatids
in humans) in metaphase II of meiosis.
9. In crossing over, parts of non-sister chromatids
exchange information that could create
new characteristics.
10. In independent assortment, there are two possibilities
of how a chromosome will sort itself
into the daughter cells. This is true for each of
the 23 pairs, so this leads to many possible
combinations.
11. Examples of chromosome mutations can
include the loss of a whole chromosome, or
part of a chromosome, the duplication of a
chromosome, or the movement of a piece of
the chromosome within itself or to another
chromosome. Students might mention fruit fly
mutations here as well.
12. Examples of genetic disorders illustrated in the
text include: Down syndrome and Edwards
syndrome.
