Chpt. 12 The Cell Cycle

what is that? The Cell Cycle

Rudolf Virchow-1855 “Omnis cellula e cellula” -every cell from a cell in this chapter we will learn how cells reproduce to form genetically equivalent daughter cells.

Cell Division

Bio 1 vocab. review : / Genome A cell’s genetic information / it’s DNA

Bio 1 vocab. review : / Genome / Chromatin DNA & protein Eukaryotic chromosomes are made of this

Bio 1 vocab. review : / Genome / Chromatin / Chromosome A package of DNA & proteins Carries genes

Chromoso mes

Bio 1 vocab. review : / Chromatid/Chromosome  somatic cell  gamete All body cells except reproductive cells Reproductive cells

Bio 1 vocab. review : / Genes “heredity unit” Composed of a specific nucleotide sequence

Bio 1 vocab. review : / Sister chromatid Replicated form of a chromosome Joined together by a centromere

Bio 1 vocab. review : / Centromere Area that joins two sister chromatids

Bio 1 vocab. review : / Kinetochore Specialized section of the centromere Made of proteins Spindle microtubules attach here

Bio 1 vocab. review : / Mitosis Division of the NUCLEUS (not the whole cell like you may have thought in Bio I !!)

Bio 1 vocab. review : / Cytokinesis Division of a cell’s cytoplasm

MITOTIC CELL CYCLE Eukaryotes

Cells duplicate their genetic material before they divide, ensuring that each daughter cell receives an exact copy of the genetic material, DNA A dividing cell duplicates its DNA, allocates the two copies to opposite ends of the cell, and only then splits into daughter cells

Mitotic Phase Interphase CELL CYCLE

CELL CYCLE Eukaryotes

êInterphase:

G1 = cell grows / produces organelles

êInterphase: G1 = cell grows / produces organelles S = duplicates chromosomes/ continues to grow

êInterphase: G1 = cell grows / produces organelles S = duplicates chromosomes/ continues to grow G2 = 2 centrosomes form cell grows organelles duplicate

êInterphase: G1 = cell growsG1 = cell grows S = duplicates chromosomes/ continues to growS = duplicates chromosomes/ continues to grow G2 = 2 centrosomes form cell grows organelles duplicateG2 = 2 centrosomes form cell grows organelles duplicate

êMitotic Phase: Mitosis Cytokinesis

êMitosis: ÊProphase = -Chromatin condenses. -Nucleolus disappears. -Spindles form. -Centrosomes move away from one another.

Non-membranous organelle / organizes spindle fibers Eventually, centrosomes migrate to opposite ends of the cell, as spindle microtubules grow out from them An aster (a radial array of short microtubules) extends from each centrosome Centrosomes:

êMitosis: ÊProphase =

êMitosis: ÊProphase = -Chromatin condenses. -Nucleolus disappears. -Spindle forms. -Centrosomes move away from one another.

êMitosis: ËPrometaphase =

êMitosis: ËPrometaphase = - Nuclear membrane breaks down. - spindles attach to kinetochores.

êMitosis: ËPrometaphase = - Nuclear membrane breaks down. - microtubules attach to kinetochore.

êMitosis: ÌMetaphase =

êMitosis: ÌMetaphase = - Centrosomes at opposite poles of cell. - chromosomes line up on metaphase plate. -kinetochores attached to microtubules.

êMitosis: ÌMetaphase = - Centrosomes at opposite poles of cell. - chromosomes line up on metaphase plate.- kinetochores attached to microtubules.

êMitosis: Í Anaphase =

êMitosis: Í Anaphase = - sister chromatids are pulled apart (into chromosomes) and go to opposite poles. -nonkinetochore fibers lengthen -cell enlarges.

êMitosis: Í Anaphase = - sister chromatids are pulled apart (to chromosomes) and go to opposite poles. -nonkinetochore fibers lengthen -cell enlarges.

How do microtubules shorten?

êMitosis: Í Anaphase kinetochore fibers shorten. this uses ATP process > illustrated

êMitosis: ÎTelophase =

êMitosis: ÎTelophase = - daughter nuclei form. -nuclear envelope forms. -chromatin uncoils. (cytokinesis begins while this stage is taking place.)

êMitosis: ÎTelophase = - daughter nuclei form. -nuclear envelope forms. -chromatin uncoils. (cytokinesis begins while this stage is taking place.)

metaphase late anaphaseearly anaphase late telophase / early cytokinesis prophase interphaseprophase late anaphase

Cytokinesis

êCytokinesis: -Animal cells = cleavage furrow actin/myosin filaments pull the cell in two like a drawstring. Outside --> In

êCytokinesis: -Plant cells = cell plate cell wall materials move (via. vesicles) to the center. Collection of cell wall material Inside --> Out

Prokaryotic organisms preceded Eukaryotes by billions of years… (we just reviewed how Eukaryotes divide)

How then do Prokaryotes divide??…

Origin of replication Cell wall Plasma membrane Bacterial chromosome E. coli cell Two copies of origin Chromosome replication begins. Soon thereafter, one copy of the origin moves rapidly toward the other end of the cell.

êCellular Division: Prokaryotes (Bacterial Cell Division) Binary Fission:  chromosome duplicates.  chromosome attaches to the plasma membrane on each end.  growth of membrane

Replication continues. One copy of the origin is now at each end of the cell. Origin

Replication finishes. The plasma membrane grows inward, and new cell wall is deposited. Cellular Division: Prokaryotes (Bacterial Cell Division) Binary Fission:  membrane cleaves.

Origin of replication Cell wall Plasma membrane Bacterial chromosome E. coli cell Two copies of origin Chromosome replication begins. Soon thereafter, one copy of the origin moves rapidly toward the other end of the cell. Replication continues. One copy of the origin is now at each end of the cell. Origin Replication finishes. The plasma membrane grows inward, and new cell wall is deposited. Two daughter cells result.

íEvolution of Mitotic Division Since prokaryotes evolved before eukaryotes, mitosis probably evolved from binary fission Certain protists exhibit types of cell division that seem intermediate between binary fission and mitosis

íEvolution of Mitotic Division 1. Binary Fission 2. Microtubular division ex. dinoflagellates 3. Nuclear division via. spindles 4. Mitosis

íEvolution of Mitotic Division Bacterial chromosome Chromosomes Microtubules Prokaryotes Dinoflagellates Intact nuclear envelope Kinetochore microtubules Kinetochore microtubules Intact nuclear envelope Diatoms Most eukaryotes Fragments of nuclear envelope