Cell Cycle WHY DO CELLS DIVIDE Reasons cells

Cell Cycle WHY DO CELLS DIVIDE?

Reasons cells divide Efficiency 2. DNA overload 3. Growth 4. Replacement 1.

Cell Division In Prokaryotes In Eukaryotes “Binary “Mitosis” DNA Fission” is copied then the cell pinches off to divide into two Cell grows and copies it’s DNA before it divides They sound the same but are very different

Important Vocabulary Chromatin: DNA is “scrunched up” in the nucleus and not visible Chromosome: cell structure that carries the genetic material Sister Chromatids: identical halves of the duplicated parent chromosome Centromere: cell structure that joins the two sister chromatids of a chromosome

Centromere Sister Chromatids

Cell Cycle WHAT IS THE CELL CYCLE?

Cell Cycle A series of events that cells go through as they grow and divide Separated into two main phases Interphase M phase

Cell Cycle Interphase “M” Phase G 1 Mitosis S G 2 Prophase Metaphase Anaphase Telophase Cytokinesis

THINK PAIR SHARE WHICH PART OF THE CELL CYCLE DO CELLS SPEND MOST OF THE TIME IN?

Which part of the cell cycle do cells spend most of the time in? SAMPLE DATA:

Interphase – G 1 Growth/Gap 1 Cells grow in size New organelles are made DNA becomes relaxed in chromatin Not visible

Interphase – S Phase Synthesis DNA is duplicated to prepare for mitosis

Interphase – G 2 Growth/Gap 2 Cells prepare for mitosis

“M” Phase – Prophase DNA organizes Chromatin condenses into visible chromosomes Chromosomes are paired with their identical copies and held together as a pair by a centromere Nuclear membrane and nucleolus disappear Spindle fibers form between pairs of centrioles Centrioles have moved to opposite ends of cell

“M” Phase – Metaphase Chromosomes line up in the middle of the cell Each chromatid is attached to a separate spindle fiber by it’s centromere

“M” Phase –Anaphase Sister chromatids are pulled apart and move away to opposite ends of cell

“M” Phase – Telophase/Cytokinesis Division of cytoplasm (cytokinesis) and the pinching in of the cell membrane allows for two identical daughter cells to form Nucleolus and nuclear membrane reappear in each cell Chromosomes begin to relax and uncoil (chromatin)

THINK PAIR SHARE WHICH PART OF THE CELL CYCLE WOULD BE A PROBLEM FOR A PLANT CELL?

Plant Cell Cycle Plasma membrane cannot pinch in during telophase/cytokinesis due to the cell wall A cell plate forms across the cell’s equator instead to aid in cell division

Cell Cycle – End Result Completion of mitosis results in two daughter cells that: Are identical copies of the parent cell Enter interphase to carry out their assigned function until they are ready to divide

Let’s practice:

Cell Cycle HOW IS THE CELL CYCLE REGULATED?

Checkpoints The cell cycle has checkpoints Control mechanism Ensures G 1, proper division/replication of cells G 2, and Mitosis

Cell Cycle WHAT HAPPENS WHEN A CELL IS NOT ACTIVELY GROWING/DIVIDING?

G 0 Phase “Resting” phase Reversible/nonreversible Cell signal

Stem Cells Unspecialized cells Embryonic Adult Stems Stem Cells cells turn into specialized cells by going through cell differentiation

Cell differentiation: when a cell changes from a stem cell to a specialized cell with a specific function

Cell Cycle WHAT IF SOMETHING GOES WRONG?

Cell Cycle & Cancer Disruption of genes that control cell growth Disruption of cell cycle

Consider: DO ALL CELLS HAVE THE SAME LIFE SPAN?