1. This is the earliest stage of sexual reproduction.
Zygote
A fertilized egg
This is the earliest stage of sexual reproduction.

2. Embryo
The earliest stage of an organism from the time of the first cell division until the time of its birth, hatching or germination.
In humans, the embryo begins when the zygote divides to create a multi-cellular organism.

3. When a sperm penetrates an egg
Fertilization
When a sperm penetrates an egg
The result of fertilization is the production of a zygote.

4. Cell Cycle
The series of events involving the growth, replication, and division of a eukaryotic cell.
The cell cycle consists of four different parts: G1 phase, S phase (synthesis), G2 phase (together known as interphase) and M phase (mitosis).

5. Interphase
The time period where cells prepare for cell division, increasing in size and copying DNA (made during the S phase.) Interphase also includes normal cell functions such as obtaining nutrients, growing, and reading its DNA.
Interphase includes the S and Gap 2 phases of the cell cycle and occurs at he beginning of the process.

6. The first part of Interphase, a step of the cell cycle
Gap 1 (G1)
Cells increase in size in Gap 1. The G1 checkpoint makes sure that everything is ready for DNA synthesis.
The first part of Interphase, a step of the cell cycle

7. In the S Phase, the cell copies its DNA.
The second part of the Interphase, a step of the cell cycle

8. The final part of Interphase, a step of the cell cycle.
Gap 2 (G2)
During the gap between DNA synthesis and mitosis, the cell will continue to grow. The G2 checkpoint makes sure that everything is ready to enter the M (mitosis) phase and divide.
The final part of Interphase, a step of the cell cycle.

9. The steps of Mitosis include:
Mitosis is the process where eukaryotic cells are copied and then divided to create new cells.
The steps of Mitosis include:
Prophase
Metaphase
Anaphase
Telephase

10. Only eukaryotic cells have a nucleus.
The brain or control center of the cell that contains all of the genetic material (DNA)
Only eukaryotic cells have a nucleus.

11. A single piece of coiled DNA and protein found in cells.
Chromosome
A single piece of coiled DNA and protein found in cells.
Chromosomes carry almost all the genetic information of cells.

12. Prophase is the first step of mitosis.
During prophase the cell will begin to organize its genetic information into chromosomes. Also it the process is determining how the cell will divide.
Prophase is the first step of mitosis.

13. Metaphase is the second step of mitosis.
Metaphase is the phase of cell division when chromosomes align along the center of the cell.
Metaphase is the second step of mitosis.

14. Anaphase is the third step of mitosis.
In anaphase the two chromatids (one half of the x) of each chromosome separate and move to opposite poles.
Anaphase is the third step of mitosis.

15. The fourth and final step of mitosis.
Telophase
A set of chromosomes is present at each end of the cell and a nuclear membrane forms around each, producing two new nuclei.
The fourth and final step of mitosis.

16. Cytokinesis takes place in the last stages of mitosis.
The process in which the cytoplasm of a single eukaryotic cell is divided to form two daughter cells.
Cytokinesis takes place in the last stages of mitosis.

17. Either of the two cells that result when a cell divides, as in mitosis
Daughter Cell
Either of the two cells that result when a cell divides, as in mitosis
Daughter cells are genetically identical to the parent cell because they contain the same number and type of chromosomes.

18. The cell must originally be an unspecialized cell.
Stem Cell
A simple cell that does not have a specific purpose or job. It can duplicate itself over and over, providing new cells.
The cell must be able to divide several times and yet still keep its undifferentiated state.
The cell must originally be an unspecialized cell.
The cell must be able to transform into a specialized cell.

19. The process where a stem cell gets a specific purpose or function.
Differentiation
The process where a stem cell gets a specific purpose or function.
A cell that is able to differentiate into all cell types of the adult organism is known as pluripotent

20. Cancer cells divide and grow more quickly than other kinds of cells.
Cancer is a disease with tumors or other uncontrolled growths that damage the body.
Cancer cells divide and grow more quickly than other kinds of cells.