Cellular Reproduction: Mitosis and Meiosis
Class Work
1. List four reasons organisms undergo mitosis.
2. List the 3 parts of Interphase.
3. Why is the metabolic activity of the cell very high during interphase?
4. How much time of the cell cycle is spent in interphase?
5. During which part of interphase does the duplication of organelles occur?
6. During which part of interphase do sister chromatids form?
7. What phase do cells enter at the end of interphase?
Homework
8. True or False: Most cells divide only once.
9. Give a brief description of what occurs during interphase.
10. How are the terms chromosomes and chromatin related?
11. During which part of interphase does DNA replication occur?
12. During which part of interphase does the cell increase in size?
13. During which part of interphase does the cell complete its growth?
14. Describe the product of mitosis.
Class Work
15. List the 6 sub-phases of the mitotic phase in order.
16. Create a simple sentence to help you remember the order of the phases.
17. Describe what occurs during each of the phases of mitosis.
18. Describe cytokinesis in animal cells.
19. Describe cytokinesis in plant cells.
Homework
20. During which phase do chromatids separate from the centromere?
21. During which phase does the nuclear membrane disappear?
22. During which phase does the nuclear envelope start to break apart?
23. During which phase do chromosomes uncoil?
24. During which phase does the nuclear envelope reappear?
25. During which phase do the centrosomes travel to opposite ends of the cell?
26. During which phase do the mitotic spindles attach to the chromosomes?
27. During which phase do the chromosomes align at the equator of the cell?
Class Work
28. At which stage do non-dividing cells become stuck?
29. Describe how cancer cells are able to metastasize.
30. Describe how and why chemotherapy and radiation are used to treat cancer.
Homework
31. Differentiate between benign and malignant tumors.
32. Describe how to recognize skin cancer.
33. Why do chemotherapy drugs cause patients to lose their hair?
Class Work
34. What is another name for “non-sex cells”?
35. Define homologous chromosomes.
36. What is another name for “sex cells”?
37. Identify the gametes in females and in males.
38. What occurs as the first step of meiosis?
39. How many divisions are there in meiosis? What is each division entitled?
40. List all 12 steps of meiosis.
41. How can two people have the exact same genetic code?
42. What process that occurs during meiosis I can lead to genetic variation?
43. During anaphase I, what happens to maternal and paternal genes?
Homework
44. How many chromosomes does a human have?
45. How many homologous chromosomal pairs does a human have?
46. How many sex chromosomes does a human have?
47. What does it mean to say, “gametes have a set of haploid chromosomes”?
48. What is the final product of meiosis?
49. How many chromosomes does each daughter cell have after Meiosis I?
50. How many chromosomes does each of the four daughter cells have after
Meiosis II?
51. Define tetrad. When does it form?
52. What occurs at a chiasma?
53. Describe what it means to say that genes “sort independently”.
Class Work
54. Identify one way in which an organism can end up with an abnormal
chromosome number.
55. Give a common example of nondisjunction.
56. What is one cause for miscarriage in the first trimester of a pregnancy?
57. Why is an older woman more likely to have a baby with Down’s syndrome?
58. Which chromosome is representative of maleness?
59. In what type of organisms is polyploidy common?
Homework
60. Identify and describe the two main types of chromosomal number
alterations.
61. What two sex chromosomes will a “normal male” have?
62. What two sex chromosomes will a “normal female” have?
63. Describe a karyotype.
64. In what type of organisms is polyploidy fatal?
65. What two factors are most influenced by having additional sex
chromosomes?
Free Response
1. Cells spend 90% of their time in interphase and only 10% in mitosis.
a. Identify and describe the three sub-phases of interphase.
b. Identify one checkpoint of cell cycle regulation that exists in
interphase and explain how this affects mature muscle cells and
neurons.
c. How would the life cycle of a rapidly dividing cell differ from that of
the cell types in part b? Give one example of a rapidly dividing cell.
2. Sexual reproduction requires that half of the chromosomes in a zygote come
from one parent and half from the second parent.
a. Describe the process by which a germ cell’s number of chromosomes
is halved in the formation of gametes.
b. Identify and describe two processes that allow for variation in
sexually reproducing organisms.
3. Mitosis results in the formation of two daughter cells with identical genetic
information.
a. Label each stage of mitosis below.
b. Complete the flow chart on the following page using the terms below:
2 daughter cells, Anaphase, Centromere, Chromosomes, Condensing,
Cytokinesis, DNA strands, Histones, Metaphase, Phases,
Prometaphase, Prophase, Sister chromatids, Telophase
4. Explain why the daughter cells produced by meiosis are genetically different
from each other, whereas the daughter cells produced by mitosis are not.
5. Errors in mitosis and meiosis can result in chromosomal abnormalities.
a. Identify and describe a common chromosomal mutation.
b. In what organism does it occur?
c. Is it harmful or beneficial to the organism?
6. Stem cells are cells that have not become specialized and have the potential
to become any type of cell in the body. There are two main types of stem
cells: embryonic and adult. Embryonic stem cells can be created by fertilizing
or cloning an egg, waiting 5-7 days until an embryo has formed and
embryonic stem cells are visible, removing the cells, and then growing the
cells in a special medium that contains nutrients and essential growth
factors. Adult stem cells are stem cells that can be found in a variety of
tissues in the body, including blood, brain, muscles, skin, teeth, heart, and
liver. They can also be removed from the body and grown in the lab. Stem
cells have already been used to treat blood cancers and could potentially be
used to cure diseases, as researchers learn more about how to regulate gene
expression to turn stem cells into exactly the kind of specialized cells needed
to replace damaged tissue.
a. Using your knowledge of cancer and how it spreads. How might stem
cell therapy be a viable option for treatment of cancer?
b. Describe the two most common methods of treating cancer. What are
some of the drawbacks to these forms of treatment?
Answers
1. Repair damaged organelles,
regenerate lost parts, grow in
size, reproduce asexually
2. Gap 1, Synthesis, Gap 2
3. The cell needs more energy
and nutrients to grow and
double its organelles
4. 90% of its time
5. Gap 1
6. Synthesis
7. Mitotic Phase
8. False, most cells divide
regularly
9. The cell doubles in size,
doubles its organelles, and
double its chromosomes.
10. Chromatin is the long thin fiber
of which chromosomes are
made of. When the chromatin
is tightly packed together it is
referred to as chromosomes.
11. Synthesis
12. Gap 1
13. Gap 2
14. An identical copy of the cell is
produced resulting in two
daughter cells
15. Prophase, prometaphase,
metaphase, anaphase,
telophase, cytokinesis
16. Anything that helps you
remember is appropriate
17. In prophase, the mitotic
spindle forms, the nuclear
envelope starts to break down,
and the centrosomes start to
travel to opposite sides of the
cell. In prometaphase, the
nuclear membrane disappears
and the mitotic spindle
attaches to the chromosomes
at their kinetochores. In
metaphase, the spindle is
completely formed and the
chromosomes line up in the
middle of the cell. In anaphase,
the chromatids separate from
the centromere and divide
toward the two poles. In
telophase cell elongation
continues, the nuclear
envelope reappears, and
chromosomes uncoil. In
cytokinesis, the cytoplasm
divides and two new cells are
formed.
18. In cytokinesis in animal cells, a
contractile ring is made when
microfilaments form around
the outside of the cell and
contract to split the cytoplasm
in two forming a clevage
furrow.
19. In cytokinesis in plant cells,
vesicles form in the center of
the cell and fuse together from
the inside towards the outside
creating a cell plate that
divides the cell in two by
creating the cell wall of each of
the two new cells.
20. Anaphase
21. Prometaphase
22. Prophase
23. Telophase
24. Telophase
25. Prophase
26. Prophase
27. Metaphase
28. G0
29. Cancer cells are able to
metastasize because they
divide uncontrollably and do
not exhibit contact inhibition
so they continue to multiply
and spread without stopping.
30. Chemotherapy is used to treat
cancer because it is able to stop
the cells from multiplying by
disrupting the cell cycle by
targeting the mitotic spindle
formation. Chemotherapy
usually targets the whole body.
Radiation is used to stop cell
division by damaging the DNA
of the cell to a point where the
cell is no longer able to direct
its own growth. Radiation can
be used to target specific areas.
31. Benin tumors are typically not
life threatening, as they do not
usually spread. Malignant
tumors are considered life
threatening as they cause
damage to surrounding areas
through metastasis.
32. You can recognize skin cancer
by checking your moles using
ABCDE. A for asymmetry, B for
border that is irregular, C for
having multiple colors, D for
diameter larger than a pencil
eraser, and E for enlarging.
33. Chemotherapy drugs typically
cause patients to lose their hair
because they interrupt the
growth cycle of all rapidly
dividing cells, which includes
hair cells.
34. Somatic cells
35. Homologous chromosomes are
two chromosomes, one from
each parent, that share the
same shape and loci for
controlling the same inherited
traits
36. Gametes
37. Females: eggs; Males: sperm
38. Chromosome Duplication
39. 2; Meiosis I and Meiosis II
40. Prophase I, Prometaphase I,
Metaphase I, Anaphase I,
Telophase I, Cytokinesis I,
Prophase II, Prometaphase II,
Metaphase II, Anaphase II,
Telophase II, Cytokinesis II
41. By being identical twins
42. Crossing over
43. Maternally and paternally
inherited homologous
chromosomes move opposite
poles.
44. 46
45. 23
46. 2
47. That gametes have one set of
23 chromosomes with no
homologous pairs
48. 4 haploid daughter cells
49. 46
50. 23
51. The pairing of homologus
chromosomes in prophase I
52. Crossing Over
53. Each homologous chromosome
separates on its own without
the influence of the other
homologous chromosomes of
that gamete. Therefore many
different assortments can be
made.
54. Non-disjunction
55. Trisomy 21
56. Incorrect chromosome number
57. The eggs of an older woman
will have been in meiosis
longer and therefore having
more of a chance for nondisjunction to occur.
58. Y
59. Plants
60. Polyploidy which is too many
sets of chromosomes and
aneuploidy which is the
addition of or lack of a
chromosome
61. XY
62. XX
63. A photographic representation
of all the homologous pairs of
chromosomes in an organism
64. Humans
65. Intelligence and Fertility
Free Response
1.
a. The three sub-phases of interphase are Gap 1 (G1), Synthesis (S), and
gap 2 (G2). During G1 the cell grows and duplicates its organelles.
During the S phase the cell replicates its DNA, doubling the number of
chromosomes it has in preparation for cell division. During G2 the cell
continues preparation for division by producing the proteins it will
need.
b. The cell has checkpoints before G1, G2, and mitosis to determine
whether or not the cell should proceed with division. Fully
differentiated (specialized) cells like muscle cells and brain cells are
said to be stuck at point G0 because the checkpoint at G1 prevents
these types of cells from undergoing further cell divisions.
c. A rapidly dividing cell, like a skin cell, would undergo multiple
divisions and likely spend less than 90% of its life in interphase.
2.
a. Meiosis is the process by which a germ cell divides and reduces the
original number of chromosomes in each cell by half. Meiosis consists
of two divisions Meiosis I and Meiosis II. During Meiosis I homologous
chromosomes shuffle genes and then are separated from one another,
resulting in two diploid cells with unique genetic information. During
Meiosis II, the sister chromatids of each cell are separated from one
another, resulting in 4 cells total, each with a haploid number of
genetically unique chromosomes.
b. Two processes that allow for variation in sexually reproducing
organisms are crossing-over and Independent Assortment. During
Prophase I of Meiosis I homologous chromosomes form tetrads and
exchange portions of their genetic material, crossing-over at the
chiasma site. During Metaphase I homologous chromosomes line up
on the metaphase plate segregate randomly and separate from one
another - this shuffling of genes is called Independent Assortment..
Independent Assortment and crossing over ensure that each sex cell
contains unique new combinations of genetic material that allows for
variation in sexually reproducing organisms.
3.
a. Prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis
b. Left to right, top to bottom
Condensing, phases, chromosomes, prophase, prometaphase, metaphase,
anaphase, telophase, DNA strands, histones, sister chromatids,
cytokinesis, centromeres, 2 daughter cells
4.
5.
6.
a. Prior to the start of meiosis and mitosis, the number of chromosomes
in the original parent cell is doubled. However, the daughter cells
produced by meiosis each contain a haploid set of unique genetic
information because the process involves two divisions and the
chromosomes are randomly shuffled and recombined before the first
division. In mitosis, the cell only divides once, separating sister
chromatids with identical genetic information into the two different
nuclei, ensuring that each daughter cell contains the same number of
identical chromosomes.
a.
a. Possibilities include polyploidy, trisomy, monosomy,
nondisjunction, anueploidy
b. b. Polyploidy – wheat, bananas, etc.; trisomy and monosomy –
humans; etc.
c. c. Polyploidy is beneficial to some organisms, but fatal in humans;
trisomy and monosomy are both harmful, but not always fatal.
a. a. Cancer cells can destroy healthy tissue, so stem cells could be used
to replace damages tissue.
b. The two most common methods of treating cancer are chemotherapy
and radiation. Chemotherapy targets mitotic spindle formation in all
dividing cells in the body, which results in death of healthy cells as
well as cancerous cells. Radiation therapy causes mutations in the
cancer cells of a tumor, but the effects of radiation, even when
targeted, may still cause mutations in healthy cells.