Download Cell Growth and Division

Cell Growth and Division – Questions and Lab
Integrated Science 2
Name:
Per:
 Read pages 735 – 746 in the IS Book and answer the following questions.
1. There are two main reasons cells divide rather than continuing to grow indefinitely. Explain them both.
a. DNA “overload”
b. Exchanging materials
2. Many organisms, especially unicellular ones, reproduce by means of ____________________. Reproduction
by mitosis is generally classified as ____________________, since the cells produced by mitosis are
genetically ________________ to the parent cell. Mitosis is also the source of new cells when a multicellular
organism _____________ and _________________. In humans, mitosis begins shortly after the egg is
fertilized, producing the vast numbers of cells needed for the ____________ to take form.
3. Chromosomes are not visible in most cells except during cell ____________________. This is because the
DNA and protein molecules that make up the chromosomes are spread throughout the __________________.
At the beginning of cell division, the chromosomes condense into compact, _________________ structures.
Before cell division, each chromosome is replicated, or _________________. Because of this, each
chromosome consists of two identical sister _______________________. When the cell divides, the “sister”
chromatids ___________________ from each other. One chromatid goes to each of the two new
__________________.
4. How many chromosomes does each body cell contain? __________. How many total chromatids? ________.
5. Describe the main events that take place in the three main stages of the cell cycle. You do NOT need to focus
on the names of the specific stages.
Interphase:
Mitosis:
Cytokinesis (include a description of how cytokinesis in plants and animals is different):
5. Cyclins are ________________ that regulate the ________________ of the cell cycle in _________________
cells.
6. Describe the two types of regulatory proteins:
a. Internal Regulators
b. External Regulators
7. What is cancer and how does it relate to cell growth regulation?
After completing the questions, begin the lab portion of the assignment. Your only materials are a light microscope
and a prepared Root Tip slide.
 Procedures/Questions.
1.
Using a compound light microscope, scan the entire length of an Allium root tip slide. Study each section of the
root tip (pointy end = tip, flat end = base) under low power and then under high power.
2.
In which region of the root (tip, base, or middle) do you find the most small tightly packed cells?
3.
Do these cells appear to be old or new?
4.
What looks like strings or bars in the nucleus are chromosomes. Examine these structures in several cells.
5.
Find some cells that you believe are in interphase. Draw and briefly describe what you see.
6.
Find some cells that you believe are undergoing mitosis. Draw and briefly describe what you see.
7.
Find some cells that you believe are undergoing cytokinesis. Draw and briefly describe what you see.
How might you tell?
2
Cell Division Notes
 Analysis and Conclusions
1. Mitosis produces two nuclei from one nucleus. The number of chromosomes in each new nucleus is the same
as that in the nucleus from which they were formed. What does this suggest must happen to the number of
chromosomes in the nucleus before it divides?
2. In which of the three main stages of the cell cycle are chromosomes duplicated?
3. Describe what might temporarily increase the frequency of mitosis in a human organ or tissue capable of
mitosis?
4. What human disease is characterized by unregulated mitosis?
 Further Study
You suspect that the frequency of mitosis in onion roots varies with the time of day. Use the worksheet below to
design an experiment to confirm or refute you suspicion.
Design Outline Worksheet
Title/Purpose:
Hypothesis:
Independent Variable (I.V.):
Continuous ___ Discontinuous ___
Levels of I.V.
(2 or more plus the control - which
must be identified)
Number of trials you will
conduct for each I.V. level
Dependent Variable:
Qualitative:
Quantitative:
3
Cell Division Notes
Constants:
4
Cell Division Notes