Chapter 7 Homework starting on page 121
Name: __________________________ Period: ____ Date: _______
1. Name 2 roles of cell reproduction, or cell division
--replacement of lost or damaged cells
--growth
--development of multicellular organisms
--asexual reproduction of single-celled organisms
2. Where do the trillions of cells in our bodies originate?
--a single fertilized egg (a zygote)
3. Where in a multicellular organism does meiosis take place?
--the reproductive organs (such as ovaries and testes in humans)
4. About how many genes do humans have? (Genes are portions of a DNA strand which
code for a particular protein)
--about 75,000
5. Chromatin (which we also think of as loosely coiled DNA) is a combination of DNA
and protein molecules.
6. Two chromatids (2 copies of the same chromosome) are joined at the centromere.
The kinetochore is a protein structure where the spindle fibers attach to the chromosome.
7. Once separated from its sister, each chromatid is considered a full-fledged
chromosome.
8. Each cell receives a complete, identical set of chromosomes.
9. About how many cells do our bodies contain?
--60 trillion
10. How often a cell divides depends on the role of the cell in the organism.
11. The cell spends most of its time in interphase. In fact, it spends 90% of its time in this
stage of the cell cycle.
12. How often do errors occur in yeast cells during cell division?
--once in 100,000 cell divisions
13. Does mitosis occur in prokaryotes? Why or why not? How could you tell this by
looking at the diagrams in the textbook?
--It does not. Prokaryotes divide through a simpler process, because they have only a
single small chromosome. You can tell the cells shown in the diagrams of mitosis are
eukaryotic because you can see the nucleus and the centrosomes.
14. Although scientists distinguish four stages of mitosis, it is a continuum.
What does this mean?
--It is a continuous process. The cell does not actually start and stop at the
beginning of each stage.
Using the diagrams and the information in your book, place the following events into the
correct phase of mitosis. Consider the second diagram in prophase prometaphase.
a. cell growth
b. nuclear envelope reforms
c. chromosomes uncoil
d. the chromosomes convene on an imaginary plate equidistant from the poles of the cell
e. sister chromatids separate
f. spindle fibers (referred to as microtubles in book)
shorter
g. motor proteins walk sister chromatids toward opposite sides of the pole
h. chromosomes condense i. mitotic spindle forms
j. nuclear envelope breaks up
k. DNA and centrosomes are duplicated (replicated)
Interphase
Cell growth
k. DNA and centrosomes are duplicated
(replicated)
Prophase
h. chromosomes condense
i. mitotic spindle forms
Prometaphase
j. nuclear envelope breaks up
Metaphase
d. the chromosomes convene on an
imaginary plate equidistant from the
poles of the cell
Anaphase
e. sister chromatids separate
f. spindle fibers (referred to as
microtubles in book) shorten
g. motor proteins walk sister chromatids
toward opposite sides of the pole
Telophase
b. nuclear envelope reforms
c. chromosomes uncoil
15. Define the following:
Centrosomes
--clouds of cytoplasmic material that in animal cells contains centrioles.
Mitotic spindle
--a football-shaped structure of microtubles that guides the separation of
the two sets of daughter chromosomes
Centrioles
--can-shaped structures made of microtubules
Cleavage furrow
--an indentation at the equator of the cell
16. How does mitosis occur differently in a plant cell?
A cell plate (a membranous disk containing cell-wall material, forms inside the
cell and grows outward). Eventually the new piece of wall divides the cell in two
Use your book and prior knowledge to label the following structures on the below
diagrams. Not all structures have a line pointing them out, so you will need to add your
own.
Cenriole
centrosome
centromere
spindle fibers
Mitotic spindle
cleavage furrow
nuclear envelope
Metaphase plate
nucleolus
17. What can result when the cell cycle control system malfunctions?
A benign or malignant tumor
18. What is cancer?
A serious disease of the cell cycle
19. What is the most dangerous attribute of cancer cells?
There ability to spread into neighboring tissues and often to other parts of the
body
20. Why is it especially alarming when cancer cells invade the circulatory system?
They can more easily travel to new locations where they can form new tumors
21. Define the following types of cancers:
Carcinomas—cancers that originate in the external or internal coverings of the
body, such as the skin or lining of the intestine
Sarcomas—arise in tissues that support the body, such as bone and muscle
Leukemias & Lymphomas—cancers of blood-forming tissues, such as bone
marrow and lymph nodes
22. Explain the two different types of cancer treatment
Radiation Therapy—Parts of the body which contain cancerous tumors are
exposed to high-energy radiation, which disrupts cell division.
Chemotherapy—Drugs that disrupt cell division are administered to the patient.
Antimitotic drugs prevent cell division by interfering with the mitotic
spindle. (Vinblastine prevents the spindle from forming, whereas Taxol
freezes the spindle after it forms).
Meiosis
23. Define the following terms:
a. somatic cell—a typical body cell (with 46 chromosomes in humans)
b. karyotype—a display in which chromosomes are photographed, dyed and
arranged in a particular way.
c. homologous chromosomes—chromosomes that carry the same sequence of
genes controlling the same inherited characteristics. These
chromosomes are slightly different versions. In other words they
contain different forms of some genes.
d. autosomes—The chromosomes other than the sex chromosomes. In humans,
these are all found in homologous pairs.
e. diploid (2n)—cells which contain pairs of homologous chromosomes.
f. haploid (n)—A cell with a single set of chromosomes.
g. gametes—reproductive cells which are haploid.
h. fertilization—One haploid cell fuses with another and produces a zygote. (In
humans a sperm cell fertilizes an egg).
i. zygote—a fertilized egg (or other type of gamete).
24. Which pair of chromosomes does not look exactly alike? (In mammalian males)
The sex chromosomes. Males have an X and a Y chromosomes. The X
chromosome is larger, and so there are genes are the X chromosome which do not have a
counterpart on the Y chromosome (the basis of sex-linked traits).
25. What are the two main differences between mitosis and meiosis?
Haploid cells are produced from diploid cells in meiosis. In other words, the
number of chromosomes is halved during two sets of divions (meiosis I and meiosis II).
An exchange of genetic material between homologous chromosomes occurs
during prophase I. This is called crossing-over and contributes to the genetic diversity of
sexually reproducing organisms.
26. What is the difference between homologous chromosomes and sister chromatids?
The two chromosomes in a homologous pair are individual chromosomes
inherited from different parents.
Sister chromatids are copies of the same chromosome resulting from DNA
replication (which takes place in the S phase of interphase).
27. In what phase of meiosis does crossing over occur?
Prophase I.
Fill out at least six similarities and differences between mitosis and meiosis in the below
Venn diagram.
Mitosis
Meiosis
*provides for growth, tissue repair,
*provides gametes for sexual reproduction
and asexual reproduction
*yields 4 haploid cells
*produces daughter cells identical to the parent cell
*crossing-over takes place during
*involves one division
*chromosomes
prophase I
*yields 2 diploid cells
Duplicated once