The Cell Cycle

The Cell Cycle As you grow, you pass through different stages in life. Your cells also pass through different stages. The life cycle of a cell is called the cell cycle. The cell cycle BEGINS when the cell is formed and ENDS when the cell divides and forms new cells. Before the cell divides, it must make a copy of its deoxyribonucleic acid (DNA).

The Cell Cycle As you know, DNA is the hereditary material that controls all cell activities, including the making of new cells. The DNA of a cell is organized into structures called chromosomes. Why copy chromosomes? To makes sure that each new cell will be an exact copy of its parent cell.

Asexual Reproduction A type of reproduction where a new organism is produced from one parent and has DNA identical to the parent organism. Offspring produced from one parent There is no genetic variation! (Hereditary information is identical from parent to offspring) http://thinktv.pbslearningmedia.org/resource/tdc02. sci.life.stru.singlecell/single-celled-organisms/

(Some organisms can produce both asexually and sexually.) Asexual Reproduction Examples of organisms who reproduce asexually: protists, bacteria, plants, fungi (Some organisms can produce both asexually and sexually.) http://thinktv.pbslearningmedia.org/resource/tdc02.sci.life.str u.singlecell/single-celled-organisms/

Types of Asexual Reproduction: Budding: Organism that produces a bud that breaks away to live on its own. Example: hydra

Types of Asexual Reproduction: Binary Fission: An organism whose cells do not contain a nucleus copy then divide into two identical organisms. Example: bacteria

Types of Asexual Reproduction: Regeneration/Fragmentation: -Regeneration uses cell division to regrow body parts -Fragmentation is when the body of the parent breaks into pieces, each of which grow into a new organism Example: planara, starfish, salamander

Types of Asexual Reproduction: Vegetative Propagation: New plants grow from parts of the parent plant (shoots or runners) Example: strawberry plant

Sexual Reproduction Two sex cells, usually an egg and a sperm, join to form a zygote, which will develop into a new organism. Requires 2 parents Sexual reproduction results in a great variety, or diversity, of offspring.

(Some organisms can produce both asexually and sexually.) Sexual Reproduction Examples of organisms who reproduce sexually: (Some organisms can produce both asexually and sexually.) Humans, animals, some plants http://thinktv.pbslearningmedia.org/resource/tdc02.sci .life.evo.redqueen/the-red-queen/

Intro to Mitosis This is one type of cell division (you learned about this in 6th grade, remember!?) http://www.teachersdomain.org/resource/tdc02.sci.life.stru.dnadivide/ (1:34)

Mitosis allows for growth and replaces worn out or damaged cells. It is the cell process in which the nucleus divides to form two nuclei identical to each other, and identical to the original nucleus, in a series of steps. Mitosis allows for growth and replaces worn out or damaged cells.

Mitosis From one cell, mitosis produces 2 cells – called daughter cells Daughter cells are identical to each other and to the original parent cell

Results of Mitosis Division of nucleus- Nuclei are identical to each other. Same number & type of chromosomes.

Mitosis The nucleus divides in several phases: IPMAT! Interphase (technically not a phase) Prophase Metaphase Anaphase Telophase

Technically not part of mitosis. Interphase Technically not part of mitosis. A resting phase.

Chromosomes replicate and nuclear membrane disappears Mitosis Prophase Chromosomes replicate and nuclear membrane disappears

Chromosomes line up in pairs along the equator – middle of cell. Mitosis Metaphase Chromosomes line up in pairs along the equator – middle of cell.

Mitosis Anaphase Chromosomes divide. Chromatids (half of a chromosome pair) separate and move to opposite ends of the cell.

Nuclear membrane forms. Mitosis Telophase Nuclear membrane forms.

Interphase                                                              Prophase                                                              Metaphase                                                              Anaphase                                                              Telophase                                                             

Video of Mitosis/Intro to Meiosis http://www.schooltube.com/video/033a8b 81d8ac4b81b0b6/ (5:34)

Meiosis Process by which the number of chromosomes is reduced by half to form sex cells. A human body cell has 46 chromosomes. Each chromosome has a similar mate, so human body cells have 23 pairs of chromosomes. Sex cells have half the number of chromosomes of a body cell, so they have 23 chromosomes, one from each of the 23 pairs.

Meiosis Since Meiosis only needs half of the number of chromosomes needed in mitosis, there are 2 divisions of the nucleus occur, Meiosis I and Meiosis II.

Meiosis II Results in 4 cells Each with ½ their number of original chromosomes

Prophase I Chromosomes replicate and nuclear membrane disappears Meiosis I Interphase DNA is duplicated Prophase I Chromosomes replicate and nuclear membrane disappears Early Prophase I Late Prophase I

Meiosis I Metaphase I Copied chromatids / chromosomes line up in middle of cell Centromeres attach to spindle fibers Anaphase I Chromatid pairs move to ends of cell. They are NOT pulled apart or separated

Meiosis I Telophase I Cells pinch apart No further replication of hereditary material There are now two cells. Both cells have full sets of genetic material (chromosomes)

Meiosis II Metaphase II Prophase II Similar to mitosis Starts with TWO cells instead of one Spindle fibers appear Metaphase II Duplicated chromatid / chromosomes line up in middle of cell Spindle fibers attach to centromeres

Anaphase II Chromatids separate & move to ends of cell Meiosis II Anaphase II Chromatids separate & move to ends of cell Telophase II Nuclear membranes form at each end of cell Cells divide There are now 4 cells!

Add the following words to your Vocabulary glossary: Asexual Reproduction Sexual Reproduction Mitosis Meiosis

Exit Slip Directions: Sexual Asexual Make a T-chart for Asexual and Sexual reproduction Then, add as many facts as you can under the appropriate column. Follow your teachers directions as to where to turn this in. Sexual Asexual

Sexual Asexual Exit Slip Directions * Place the following words/phrases in the correct column: 2 parents can adapt to changes 1 parent cannot adapt to changes Identical offspring uses process of meiosis Unique offspring uses process of mitosis Teacher note: print slide for easier use Sexual Asexual