Name _____________________Hr_____ Date___________
We are all made of trillions of cells. Scientists have wondered for years about the nature of cells and how they work. They have researched and found answers to many questions in order to better understand how organisms work. Some of the questions they have found answers to include:
What happens to our cells as we go through life?
What happens to them as we grow?
What happens to them when we mature and stop growing?
How to cells increase in number?
What causes a cell to change?
What is the cell cycle ?
Do all cells change the same way?
What is mitosis ?
What is cytokinesis?
Lets look at some of these questions and discuss what scientists have learned.
1.
As we go through life our cells are constantly changing. All different sorts of cells are growing, dividing, and dying. Old skin cells are wearing out, dying, and flaking off as new ones are formed underneath. Red blood cells are wearing out and being broken down as new ones are being created at a rate of around two to three billion a second in your bones. Your muscle cells are getting larger as you grow and exercise.
Look at the different cells below. They look different (different structure) because they have different jobs (different functions). What they look like (structure) is largely determined by what they do (function). Label the different cells below and on the next page and write what their jobs (functions) are.

2.
Just as organism go through a life cycle of being born, developing, growing, and dying, so do cells. In simple one celled organisms such as bacteria, when a cell divides the whole organism is being reproduced. In more complex organisms cells grow and divide to keep the organism alive and healthy. The process is called the Cell
Cycle. The steps of the cell cycle show a person how the cell duplicates (copies) everything inside of it so that at the end of the process there are two cells instead of one. The cell cycle happens in two main steps . Mitosis is the process where the cell nucleus divides to form two identical nuclei. Cytokinesis is the process where the cytoplasm divides to form two identical daughter cells.
Below sketch the circle on page 100 which represents the cell cycle. a. What are the two longest parts of the cell cycle? ___________ & _________

b. How long does the mitosis phase normally last? ____________ c. How long does the cytokinesis phase last? _________________ d. How long does interphase last? ___________________
3.
Before learning about mitosis its important to learn about the parts in the cell involved in mitosis. a. Chromatin : The nuclear material found in the nucleus made of DNA. When the cell begins to divide the chromatin begins to form the chromosomes. Draw it.
(page 98 - the genetic material inside the nucleus at interphase) b. Chromosome : Structures that contain the cells DNA - On the chromosomes are genes which carry information for different characteristics, traits, and functions.
For example one gene may carry the information for color hair, another for shape of ear, another for shape of tongue. Humans have 23 pairs of chromosomes (46 total).
Other organisms have more or less (fruit flies have eight). Draw one. (page 97) c. Chromatid label one (page 97
: A single strand of the double stranded chromosome. Draw and d. Centromere : The structure that holds the two strands of a chromosome
together. Draw and label one (page 97) e. Centrioles : Small structures which go to the poles in prophase to which spindle fibers are attached. Draw one with spindle fibers (page 98-99) f. Spindle fibers : The net-like fibers that extend across the cell from centrioles to the chromosomes and along which chromosomes travel Draw them along with the centrioles as noted during metaphase on page 99.
4.
Now lets sketch the mitosis phases using the figure on pages 98 and 99 of your text. . Next to each step describe what is happening inside the cell (see page 98-
99) . Use the terms you have learned in paragraph three above to help you.

1. Prophase:
3. Anaphase:
Cytokinesis:
2.
4.
Metaphase:
Telophase:
6. DNA Replication and Final Cell Division Vocabulary
Structure and Replication of DNA: We mentioned earlier that the cell’s DNA (Deoxyribonucleic acid) is found in its nucleus and during the cell cycle is replicated (copied) so that each daughter cell has the same amount of DNA as the original cell before it divided. Read pages 101 and 102

to get a better understanding of how DNA copies (replicates) itself. Below, draw a sketch of the
DNA strand replicating itself (102).
Vocabulary:
RNA: One-stranded nucleic acid that carries the DNA message to ribosomes outside the nucleus and helps the ribosomes make proteins fertilization : The joining of egg and sperm zygote : A fertilized egg. gene : A section of DNA on a chromosome that is responsible for a specific trait or characteristic like hair color or shape of nose or for making a certain protein. mutation : A permanent change in a gene or a chromosome. haploid : A cell that has one of every kind of chromosome. The cell has a haploid number of chromosomes. Only sex cells have a haploid number of chromosomes. diploid : A name for a cell that has two of every type of chromosome. The cell has a diploid number of chromosomes. Every cell in your body is diploid except your sex cells.