Download Activity: Mitosis—Editing for Accuracy - Spring

Team Members:
Scenario: Mitosis—Editing for Accuracy
Online, user-written encyclopedias (like Wikipedia) are convenient, tertiary sources of general information
(tertiary literature: often intended for general audience, typically presents basic information on a topic with limited
context; often not peer-reviewed; examples include newspapers, magazines, encyclopedias and reference guides).
However, students have drawn criticism from their instructors (and lost points on research papers and
assignments) for the citations of these sources in assignments that are designed to engage them in the primary or
select secondary literature of a field of study (primary literature: includes original research published in peer-reviewed
journals. Secondary literature: works that summarize and synthesize knowledge in a particular area of research; examples
include ‘review’ articles that may be published in peer-reviewed journals).
University faculties typically discourage the use of online, user-written encyclopedias because:
1. As an encyclopedia, they typically contain basic information that is often of limited scholarly use—
encyclopedias may be useful if they lead to more comprehensive and relevant primary sources.
2. The entries may be authored/edited by anonymous, potentially unqualified individuals—a policy that
may foster serious inaccuracies in their content and cause that content to be unstable over time.
As an example, consider the inaccuracies found in the entry for ‘interphase’ below:
Interphase: Eukaryotic cells that are destined to divide, progress through a series of stages known as the cell
cycle. Included in these stages are G1, S, and G2 phases, which are collectively known as interphase. G1 is a
period in which chromosomes are replicated in preparation for cell division. In S the cell synthesizes proteins
that are necessary for chromosome sorting and cell division. During G2 the mitotic spindle is formed—
structures that will be utilized to organize and sort chromosomes during nuclear division. Following interphase
the cell will advance into the M phase of the cell cycle where mitosis occurs.
Several of these encyclopedias have responded to the criticisms about the reliability of the content by
establishing a staff of content experts to edit entries for accuracy. You will work in small collaborative groups
that will act as an editorial staff for a hypothetical, online user-written encyclopedia.
Use the information above to answer the following questions:
1. Included in the entry for ‘interphase’ is the statement: “G1 is a period in which chromosomes are replicated in
preparation for cell division.” This statement
a. is accurate
b. is accurate but incomplete, as it doesn’t account for differences in plants during G1
c. is inaccurate—chromosome replication occurs in G2 not G1
d. is inaccurate—chromosome replication occurs in S not G1
2. If information about the time required for each stage were to be included in the entry, which statement would be
accurate?
a. G1 is typically the longest phase
b. S is typically the longest phase
c. G2 is typically the longest phase
d. The stages typically take the same amount of time to complete
3. Included in the entry for ‘interphase’ is the statement: “In S the cell synthesizes proteins that are necessary for
chromosome sorting and cell division.” This statement
a. is accurate
b. is accurate but incomplete, as it doesn’t account for differences in plants during S
c. is inaccurate—proteins necessary for chromosome sorting are produced in G1
d. is inaccurate—proteins necessary for chromosome sorting are produced in G2
4.
Included in the entry for ‘interphase’ is the statement: “During G2 the mitotic spindle is formed.” This statement
a. is accurate
b. is accurate but incomplete, as it doesn’t account for differences in plants during G2
c. is inaccurate—this is an event of mitosis not interphase
d. is accurate but incomplete, as it doesn’t account for differences in fungi during G2
5. Online, user-written encyclopedias
a. are an example of primary literature
b. are stable over time and less likely to contain fewer inaccuracies than primary media
c. may be of value if they lead users to more comprehensive primary literature on a topic
d. are an example of secondary literature
Activity: Mitosis—Editing for Accuracy
Because of your expert knowledge of cell division, you and your colleagues have been hired by an established
online, user-written encyclopedia as content editors. Your job is to read entries submitted on topics about cell
division and edit them for accuracy.
Mitosis (Overview)
Mitosis is one component of all cell’s cycle. Strictly speaking, mitosis refers to division of the cytoplasm.
Mitosis is typically followed by the division of the cell into two cells, a process called metastasis. In mitosis,
the two resultant daughter nuclei are identical to one another, and to the mother nucleus. The process occurs in
a series of steps that, when they occur properly, ensures that each daughter nucleus receives the appropriate
genetic information, which is found in discrete bodies known as centromeres.
Chromosomes
Cells store their genetic information in discrete bodies known as chromosomes. Typically chromosomes consist
of a single linear double stranded DNA molecule that is wrapped around carbohydrates called wraptones
forming chromatin. Prior to mitosis (in G2 of interphase) the chromosomes are replicated and exist as two
bodies that are attached at a site known as the nucleosome. The two identical bodies of a replicated
chromosome are called sister histones. During mitosis two chromatids will go to the left side of the cell leaving
the right side of the cell without a chromatid.
Phases of Mitosis
Mitosis is a dynamic process. For purposes of description it is typically broken down into phases which are
briefly described below:
Prophase: Chromosomes condense; nuclear membrane breaks down; mitotic spindle begins to form;
kinetochores begin to migrate to the two poles. Chromosomes are aligned at center of cell.
Metaphase: Chromosomes separate and migrate to opposite poles.
Anaphase: Spindle apparatus completes formation; sister chromatids are attached to spindle fibers via
histone proteins.
Telophase: Nuclear membrane forms around each set of chromosomes; chromosomes decondense.
Although not a part of mitosis, the division of the cytoplasm, called cytokinesis, typically occurs during
prophase.
Use your knowledge of the cell cycle and the information above to answer the following questions:
1. A typical human epithelial cell in G2 of interphase would possess
a. 23 replicated chromosomes
b. 46 unreplicated chromosomes
c. 96 unreplicated chromosomes
d. 23 unreplicated chromosomes
e. 46 replicated chromosomes
2. A human skin cell is observed. It is found to have two distinct nuclei each having 46 unreplicated
chromosomes. These observations would be seen if the cell is in____.
a. G2 of interphase
b. metaphase of mitosis
c. S of interphase
d. telophase of mitosis
e. prometaphase of mitosis
3. A substance is found to interfere with a dividing cell’s ability to polymerize tubulin proteins into
microtubules. With which aspect of cell division would this substance interfere?
a. the replication of chromosomes
b. the condensation of chromosomes
c. the formation of the mitotic spindle
d. the loosening of chromosomes into chromatin
e. cytokinesis
4. The Journal of Cell Biology, Cell, Molecular Biology of the Cell and Molecular and Cellular Biology
are peer-reviewed journals that publish original research papers on aspects of cellular biology, including
cell division. These journals are examples of
a. tertiary literature
b. user-written encyclopedias
c. secondary literature
d. unacceptable sources of information for student research papers
e. primary literature