Key Concepts:
-What events take place during the three stages of the cell cycle?
-How does the structure of DNA help account for the way in which DNA copies
itself?
PRENTICE HALL - CELLS AND HEREDITY
CHAPTER 2 – CELL PROCESSES AND ENERGY
Section 3 – Cell Division
Key Terms and
Connections
Cell Cycle----------------->
Main Ideas and Visuals
Questions and
Comments
Stage 1: Interphase
-The cell cycle is the regular sequence of growth
and division that cells undergo.
-During the cell cycle, a cell grows, prepares for
division, and divides into two new cells, (daughter
cells) which begin the cycle again.
-Interphase is the first stage of the cell cycle, and it
is the period before cell division.
*During interphase, the cell grows, makes a
copy of its DNA, and prepares to divide into two
cells.
Growing:
-During the first part of interphase, the cell grows to
its full size and produces structures it needs.
E.g. Some of these productions include making
new ribosomes and enzymes, and copying the
mitochondria and chloroplasts.
Replication---------------->
Copying DNA:
-Replication is a process that occurs in the next
part of interphase, and it is when the cell makes an
exact copy of the DNA in its nucleus.
-DNA holds all the information needed by a cell to
survive, therefore replication of DNA is extremely
important as each daughter cell cannot survive
without a complete set of DNA.
-In the end of DNA replication, the cell contains two
identical sets of DNA.
Preparing for Division:
-The cell then produces structures that it will use to
divide into two cells, thus at the end of the
interphase, the cell is ready to divide.
-What sorts of structures
are produced?
Organelles?
Mitosis
Mitosis----------------------> -Mitosis is the second stage of the cell cycle, and it
is the stage during which the cell’s nucleus divides
into two new nuclei.
*During mitosis, one copy of the DNA is
distributed into each of the two daughter cells.
-Mitosis is divided into four stages: prophase,
metaphase, anaphase, and telophase.
Chromosomes-----------> -Chromosomes are the double-rod structures
formed during prophase when the chromatin
compacts.
-Each chromosome has two rods (chromatids) held
together by a centromere because the cell’s DNA
has identically replicated into the two rods
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-As the cell goes through metaphase, anaphase,
and telophase, the two chromatids separate and
move to opposite ends of the cell.
-Two nuclei then form around the chromatids at the
two ends of the cell.
Cytokinesis--------------->
Stage 3: Cytokinesis
-Cytokinesis is the final stage of the cell cycle and it
completes the process of cell division.
-During cytokinesis, the cytoplasm divides. The
organelles are distributed into each of the two
new cells.
-Cytokinesis usually starts at the same time as
telophase.
-When this stage is complete, two daughter cells,
each with the same number of chromosomes as
the original parent cell, have formed.
-After cytokinesis, each daughter cell enters
interphase to being the cycle again.
Cytokinesis in Animal Cells:
-During cytokinesis in an animal cell, the cell
membrane tightly squeezes together around the
middle of the cell until the cytoplasm pinches into
two daughter cell.
-Each daughter cell has about half the organelles.
Cytokinesis in Plant Cells:
-Due to a plant cell’s rigid cell wall, cytokinesis is
somewhat different in plant cells.
-A structure called a cell plate forms across the
middle of the cell, and gradually develops into new
cell membranes between the two daughter cells.
-New cell walls form around these membranes.
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Structure and Replication of DNA
-How long does the
cytokinesis stage take?
How long does it take for
a cell to divide and
undergo the whole cell
cycle?
-DNA replication ensures that each daughter cell
will have the genetic information needed to carry
out its functions.
-Rosalid Franklin’s X-ray photographs of DNA
molecules in 1952 helped James Watson and
Francis Crick determine the structure of DNA in
1953.
The Structure of DNA:
-A DNA molecule looks like a spiral staircase.
-The two sides of the DNA ladder are made up of
deoxyribrose (sugar molecule) alternating with
phosphates.
-Each ring is made up of nitrogen bases (molecules
that contain nitrogen and other elements).
-DNA has four kinds of nitrogen bases: adenine,
thymine, guanine, and cytosine.
-The bases on one side of the ladder pair up with
the bases on the other side.
-Adenine only pairs with thymine, and guanine only
pairs with cytosine.
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The Replication Process:
-During DNA replication, a DNA molecule
separates between its paired bases, and new
bases pair on each old strand. This results in the
-I am still a bit confused
formation of two identical DNA strands.
regarding exactly how
-Next, nitrogen bases floating in the nucleus pair up this process works.
with the bases on each half of the DNA molecules.
*Because of the specific way in which nitrogen
bases pair with one another, the order of the
bases in each new DNA molecule exactly
matches the order in the original DNA
molecule.
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The Cell Cycle:
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