MITOSIS PRACTICE PROBLEMS- ANSWERS
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Answers
Repair damaged organelles,
regenerate lost parts, grow in size,
reproduce asexually
Gap 1, Synthesis, Gap 2
The cell needs more energy and
nutrients to grow and double its
organelles
90% of its time
Gap 1
Synthesis
Mitotic Phase
False, most cells divide regularly
The cell doubles in size, doubles its
organelles, and double its
chromosomes.
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.
Synthesis
Gap 1
Gap 2
An identical copy of the cell is
produced resulting in two daughter
cells
Prophase, prometaphase,
metaphase, anaphase, telophase,
cytokinesis
Anything that helps you remember
is appropriate
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
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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.
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.
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.
Anaphase
Prometaphase
Prophase
Telophase
Telophase
Prophase
Prophase
Metaphase
G0
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.
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
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own growth. Radiation can be used
to target specific areas.
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.
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.
Chemotherapy drugs typically cause
patients to lose their hair because
they interrupt the growth cycle of
all rapidly dividing cells, which
includes hair cells.
Somatic cells
Homologous chromosomes are two
chromosomes, one from each
parent, that share the same shape
and loci for controlling the same
inherited traits
Gametes
Females: eggs; Males: sperm
Chromosome Duplication
2; Meiosis I and Meiosis II
Prophase I, Prometaphase I,
Metaphase I, Anaphase I, Telophase
I, Cytokinesis I, Prophase II,
Prometaphase II, Metaphase II,
Anaphase II, Telophase II,
Cytokinesis II
By being identical twins
Crossing over
Maternally and paternally inherited
homologous chromosomes move
opposite poles.
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46
23
2
That gametes have one set of 23
chromosomes with no homologous
pairs
4 haploid daughter cells
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23
The pairing of homologus
chromosomes in prophase I
Crossing Over
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.
Non-disjunction
Trisomy 21
Incorrect chromosome number
The eggs of an older woman will
have been in meiosis longer and
therefore having more of a chance
for non-disjunction to occur.
Y
Plants
Polyploidy which is too many sets of
chromosomes and aneuploidy
which is the addition of or lack of a
chromosome
XY
XX
A photographic representation of
all the homologous pairs of
chromosomes in an organism
Humans
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.
a. 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.
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.
5.
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.
6.
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.