GR Chapter 12: Cell cycle (interphase and mitosis) Name: ____________ Per: ________
We will learn ch. 12 out of order….starting with 12.3 = interphase and cell cycle control
Vocabulary: chromosome vs. chromatin vs. sister chromatids, centromere, interphase vs.
mitosis vs. cytokinesis, spindle fibers, kinetochore, mitosis vs. binary fission, checkpoint, cyclin, cancer, metastasis
Concepts:
12.1 Overview
--our goal in cell division is to make sure the two cells have the same ________ at the end
--to make sure that this is done correctly, the cell takes the long, thin form called _____________ and packs it up into condensed ____________________ (this can be split up more easily) --when we first see these in a microscope, they look like an X – this is actually two ___________ ______________ that are combined together at the ____________ region --read the last part carefully, we will see it summarized in a diagram again in ch. 13
--cell division serves 3 basic purposes (figure 12.2) … humans only use it for 2 of these below
*remind yourself why multicellular organisms grow by increasing the number of cells, not the size of cells (fig. 6.7)
12.3 Regulation of cell cycle
--some cells in the human body do not seem to divide at all – for example, ______________ --these cells seem to be locked in interphase, never leaving (fig. 12.15b)
--explain the general concept of a checkpoint in the cell cycle
--what controls moving past checkpoints? signaling pathways … often involving what proteins (bottom right p. 229)
Living cells go through a series of stages known as the cell cycle. Each stage has built in “checkpoints.” Checkpoints are labeled on the diagram below.
Discuss the main events in each stage of the cell cycle. Make sure to describe when checkpoints occur and what these checkpoints are “checking” for.
G1 phase.
-- What might happen if the G1 checkpoint malfunctions? S phase.
There is no specific protein controlled checkpoint associated with S phase. However, the cell does have enzymes that check for errors in DNA replication.
--What enzyme initiates this error checking function? (you will need to look in ch. 16.2, pg. 305)
G2 phase.
--What might happen if the G2 check point stopped working in cells?
M phase.
--what could occur if the M phase checkpoint (during anaphase) malfunctions?
--The period between cell divisions is known as ___________________.
--Look back at the cycle diagram. In what phase of the cell cycle, does the cell spend most of its life cycle? ________________
Internal Control:
What class of macromolecules make up the cell cycle control system? ______________ --What is the “go ahead” signal for cells to pass from G2 into Mitosis?
The cell cycle (and corresponding fluctuations in MPF and cyclin) is another example of a signaling pathway. (fig. 12.16 a pg 230)
--label the 5 “steps” of the cycle. Briefly tell what happens to concentration of Cdk,, cyclin, and MPF in fig 12.16 pg. 230)
--What is MPF _______________ _________________ ________________? --What is its main function
--Describe the relative concentrations of MPF and its constituent molecules throughout the cell cycle.
a. MPF b. Cdk c. cyclin
External: Explain density dependent inhibition and anchorage dependence
--the production or activation of these proteins might be connected to outside environmental signals
--out of control cell division is the general definition of __________________
--Cancerous cell may not need _________ _________ , or they may make their own growth factors, or they may stop dividing at ___________ poins during the cell cycle.
--What are HeLa cells?
--why does chemotherapy often have debilitating side effects (nausea, hair loss, fatigue)
--The body’s ____________ system normally recognizes cells that have undergone__________ ; --however cancerous cells can and do develop ways to evade destruction.
--Though the causes of cancer are diverse and numerous they all seem to result from some transformation in __________ that control the cell cycle.
What is the difference between a benign and malignant tumor?
12.2 Specifics of cell cycle (eukaryotic cells ONLY)
--broadly, the cell cycle consists of three broad phases:
--which of these phases is by far the longest (pie chart p. 221)? __________________________ --interphase has 3 subphases –discussed in section 12.3
They were: ____________________, ___________________, and _________________ --mitosis has many subphases … we study them separately, but know that mitosis is a cycle where one subphase cycles into the next one
--early in mitosis (preparing for dividing up the DNA equally) a) packing up the DNA code – before in interphase, it was in
_______________________ form, but now it is packing up into the “X” shape which is ________________ ____________________ form
--identical copies are tied together due to interactions between their central regions of DNA called ________________________
b) if the DNA is to be split up and moved to separate parts of the cell, then the ________________________ must be temporarily taken apart (and then rebuilt at the end once the DNA is split)
c) the spindle fibers network is constructed to pull the DNA apart … they will attach to a specific protein within the centromere region called
_____________________
1) _________________________ 2) _________________________ 3) _________________________
--middle of mitosis
--draw a picture of what the DNA looks like lined up in mitosis
--they are lined up so that the _____________________ ____________________ are split apart in mitotic cell division … note that the homologous
chromosomes are NOT paired together in the lineup (like they are in meiosis I when gametes are forming)
--____________________ __________________ within kinetochore complex spend ATP to walk DNA apart along spindle fibers that attached earlier --look back at section 12.3; review the purpose of the checkpoint that occurs during anaphase. What could happen if this checkpoint malfunctions?
--late in mitosis
--now that the DNA has been separated equally, the ____________________ begins to re-form around it
--after interphase and mitosis, ______________________ occurs - what happens here?
--now that we have discussed the cell cycle in detail, give me the big picture summary – what is the goal of mitosis?
Mitosis and meiosis
Cells divide into two different ways to make new cells. Mitosis
Mitosis is used to produce daughter cells that are genetically identical to the parent cells. The cell copies - or 'replicates' - its chromosomes, and then splits the copied chromosomes equally to make sure that each daughter cell has a full set.
Meiosis
Meiosis is used to make special cells - sperm cells and egg cells - that have half the normal number of chromosomes. It reduces the number from 23 pairs of chromosomes to 23 single chromosomes. The cell copies its chromosomes, but then separates the 23 pairs to ensure that each daughter cell has only one copy of each chromosome. A second division divides each daughter cell again to produce four daughter cells.
Mitosis
Your body contains trillions of cells (thousands of millions). But you started life as a single cell - a fertilized egg cell. This cell then divided and divided to make more cells through a process called mitosis.
Mitosis is a way of making more cells that are genetically the same as the parent cell. It plays an important part in the development of embryos, and it is important for the growth and
development of our bodies as well. Mitosis produces new cells, and replaces cells that are old, lost or damaged.
Before mitosis, the chromosomes are copied. They then coil up, and each chromosome looks like a letter X in the nucleus of the cell. The chromosomes now consist of two sister chromatids. Mitosis separates these chromatids, so that each new cell has a copy of every chromosome.
A diagram of a cell ready for mitosis. The copied chromosomes consist of two chromatids joined at the centromere
