Cell Division Mitosis vs. Meiosis ….the battle continues
Mitosis • Type = Asexual reproduction • Growth, maintenance, and repair • Takes place in somatic (body) cells
Cell Cycle • Interphase Cells are in interphase 90% of the time. • G1- growth • S - chromosome replication • G2- Prepare for mitosis • Mitosis (nuclear division) • Cytokinesis (cytoplasmic division)
Overview of Mitosis Mama Cell=2n (diploid) Daughter cell= 2n (diploid) Daughter cell= 2n (diploid)
Interphase (pre game show) • Chromosomes are copied (# doubles) • Chromosomes appear as threadlike coils (chromatin) at the start, but each chromosome and its copy(sister chromosome) change to sister chromatids at end of this phase
PROPHASE CENTRIOLES APPEAR AND MOVE TO OPPOSITE ENDS OF THE CELL Spindle fibers form between centrioles
METAPHASE • Chromosomes “meet” in the middle. Spindle fibers attach to the centromere of each chromosome.
ANAPHASE • Sister chromatids separate from each other and are “pulled” to opposite ends of the cell.
Telophase • Cell plate forms and cell membrane begins pinching in= “cleavage.” • Chromosomes look like threads (chromatin) again. Nuclear envelope forms again.
Cytokinesis • Division of the cytoplasm • Cell membrane completely pinches off. • Cycle starts again.
Rounds of Cell Division • One
Number of daughter cells • Two, each identical to each other and the parent.
Meiosis • Type: Sexual Reproduction • Purpose: To create haploid gametes • Takes place in gametes (sex cells/egg and sperm cells)
Meiosis • Types of cells that undergo meiosis: Gametes (sex cells) • Egg and sperm
Meiosis: Overview Parent Cell: diploid= 2n After Meiosis I After Meiosis II Daughter Cells:Haploid= n ; and all genetically different from eachother and parent cell
??? Why would it be important for the gametes to contain half as many chromosomes as a somatic cell?
Meiosis I Prophase I: Crossing Over occurs to create genetic variability.
Meiosis I: Metaphase I • Homologous chromosomes line up in the middle different from mitosis!
Meiosis I: Anaphase I • Chromosomes pull apart
Meiosis II • 2nd round of division
Meiosis II: Prophase II • 2 cells now • Centrioles appear and move to opposite ends
Meiosis II: Metaphase II • Chromosomes line up in the middle
Meiosis II: Anaphase II • Sister chromatids pull apart and move to opposite ends DRAW IT YOURSELF
Chromosome number in Meiosis • Mother cell-2n (Diploid) • Daughter cells- n (Haploid)
Round of cell division • Two • Illustrate mother cell with four chromosomes (2n) and daughter cells with two chromosomes (n) in each. Make sure to include replication before meiosis I.
Number of daughter cells • Four
Let’s compare! • http://www.teachersdomain.org/resources/tdc02/sci/life/gen/mitosis/index.html
Ticket to the Lab • Name 3 key differences between mitosis and meiosis on your foldable.