Download HW 10/29 Mitosis

Name: ________________________________
Mitosis
Directions: Read and Highlight then answer the questions.
At the end of interphase, the cell has made duplicates of everything in preparation for dividing. As the cell
begins to divide, it goes through a process called mitosis. In mitosis, the nucleus divides followed by the
cytoplasm dividing, resulting in two cells. After the cytoplasm divides, cell division is complete.
Scientists say that one parent cell, or the dividing cell, forms two identical daughter cells (kind of like twins).
Each cell has an identical set of DNA (chromosomes), and this DNA is also identical to that of the parent cell. If
the cell cycle is not carefully controlled, it can cause a disease called cancer, which causes cell division to
happen too fast. A tumor can result from this kind of growth.
The genetic information of the cell, or DNA, is stored in the nucleus
specifically in the organelle called chromosomes. The creation of an exact
copy of DNA by the chromosomes insures that the cells are identical. Each
organism has a unique number of chromosomes. In human cells, our DNA
is divided up into 23 pairs of chromosomes. The picture to the right has a
DNA molecule on the left and a chromosome on the right (shaped like an
“X”).
1. Why must your cells be perfect when making new cells?
The Four Phases of Mitosis
Mitosis is divided into four phases:




Prophase: This is the beginning phase. The membrane that surrounds the nucleus disappears so
everything inside the nucleus is just floating in the cytoplasm. The chromosomes that usually look like
loose strings tighten up and pull together.
Metaphase: The chromosomes line up in the center of the cell. The chromosomes line up in a row, one on
top of the next. It almost looks like a dance is getting ready to happen in the center of the cell.
Anaphase: The copies of each chromosome separate moving to opposite sides of the cell resulting in two
sets of identical chromosomes. The separate like opposite ends of a magnet pushing as far apart as
possible.
Telophase: A nuclear membrane forms around the chromosomes in both cells. Each new nucleus contains
the exact same number and type of chromosomes as the original cell.
2. In what phase of mitosis are chromosomes moving toward opposite sides of the cell?
a. Prophase
b. Metaphase
c. Interphase
d. Anaphase
e. Telophase
f. Cytokinesis
Mitosis is simply the creation of two new nuclei (more than one nucleus). At the end of mitosis, the cell
actually separates in a process called cytokinesis or division of the cytoplasm. It’s kind of weird, but this part
of the process happens after mitosis. When the cells separate, they produce two identical cells, each with its
own nucleus. That sounds confusing so let’s repeat that. Mitosis is everything just before the cell splits in half.
Cytokinesis is what we call the cell separating into two cells (the division of the cytoplasm).
3. What is the term for the division of the cytoplasm?
a. Prophase
b. Metaphase
c. Interphase
d. Anaphase
e. Telophase
f. Cytokinesis
If you look at the picture to the left, this is
a representation of dividing plant cells.
Each box represents one cell. When the
cell has 1 or 2 nuclei, the cell is in
interphase. These cells look like they have
little black dots in them. This is when all of
the organelles are duplicating. You can see
that most of the cells in the picture are in
interphase.
The cells that have squiggly lines
(chromosome) in them are going through
mitosis. The squiggly lines look like
spaghetti.
4. In which phase do cells spend most of their time?
a. Prophase
b. Metaphase
c. Interphase
d. Anaphase
e. Telophase
f. Cytokinesis