Cell Division / Cell Reproduction

Chromosome (Package for DNA during Cell Chromosome (Package for DNA during Cell Division)Division)

Homologous PairHomologous Pair

One from each One from each parentparent

23 pairs of 23 pairs of chromosomes (n)chromosomes (n)

HaploidHaploid

46 total 46 total chromosomes (2n)chromosomes (2n)

DiploidDiploid

Chromosomes – Packaging Genetic MaterialChromosomes – Packaging Genetic Material

Sex Chromosomes XX = FemaleSex Chromosomes XX = Female

Cell Cycle

Cell Division / Cell ReproductionMitosis and Meiosis

Take notes a Take notes a quiz follows:quiz follows:

The Cell CycleThe Cell Cycle

S

Prophase

Prometaphase

Metaphase

Anaphase

Telophase &

Cytokinesis

Go

G1

G2

Interphase G1Interphase G1

• The G1 phase, or Gap 1 phase, is the first of four phases of the cell cycle that takes place in eukaryotic cell division. In this part of interphase, the cell grows in size and synthesizes mRNA and proteins in preparation for subsequent steps leading to mitosis. G1 phase ends when the cell moves into the S phase of interphase.

Interphase SInterphase S

• S-phase (synthesis phase) is the part of the cell cycle in which DNA is replicated, occurring between G1 phase and G2 phase. Precise and accurate DNA replication is necessary to prevent genetic abnormalities which often lead to cell death or disease

DNA Replication

Interphase G2Interphase G2

• G2 phase is a period of rapid cell growth and protein synthesis during which the cell readies itself for mitosis

Interphase GInterphase G00

• The G0 phase (referred to the G zero phase) or resting phase is a period in the cell cycle in which cells exist in a quiescent state.

• G0 phase is viewed as either an extended G1 phase, where the cell is neither dividing nor preparing to divide, or a distinct quiescent stage that occurs outside of the cell cycle.[1]

• Some types of cells, such as nerve and heart muscle cells, become quiescent when they reach maturity (i.e., when they are terminally differentiated) but continue to perform their main functions for the rest of the organism's life.

DNA replication in eukaryotes is followed by the process called mitosis which assures that each daughter cell receives one copy of each of the replicated chromosomes. During the process of mitosis,the chromosomes pass through several stages known as prophase, metaphase, anaphase and telophase. The actual division of the cytoplasm is called cytokinesis and occurs during telophase.During each of the preceding stages, particular events occur that contribute to the orderly distribution of the replicated chromosomes prior to cytokinesis.

InterphaseInterphase• A normal resting cell exists in a

state called interphase in which the chromatin is undifferentiated in the heavily-stained nucleus, as illustrated above.

• Before the cell enters the mitosis phase, it first undergoes a synthesis or S phase where each chromosome is duplicated and consists of two sister chromatids joined together by a specific DNA sequence known as a centromere.

• Centromeres are crucial to segregation of the daughter chromatids during mitosis.

chromatin

nucleolus

interphase prophase prometaphase

anaphasemetaphase telophase

A quick overview of cell divisionThe genetic information of plants, animals and other eukaryotic organisms resides in several (or many) individual DNA molecules, or chromosomes. For example, each human cell possesses 46chromosomes, while each cell of an onion possesses 8 chromosomes. All cells must replicate their DNA when dividing. During DNA replication, the two strands of the DNA double helix separate, and for each original strand a new complementary strand is produced, yielding two identical DNA molecules. DNA replication yields an identical pair of DNA molecules (called sister chromatids) attached at a region called the centromere.

Sister Chromatids

Stages of MitosisStages of Mitosis• Prophase. During prophase, the chromosomes supercoil and

the fibers of the spindle apparatus begin to form between centrosomes located at the pole of the cells. The nuclear membrane also disintegrates at this time, freeing the chromosomes into the surrounding cytoplasm.

• Prometaphase. During prometaphase, some of the fibers attach to the centromere of each pair of sister chromatids and they begin to move toward the center of the cell.

• Metaphase. At metaphase the chromosomes have come to rest along the center plane of the cell.

• Anaphase. During anaphase, the centromeres split and the sister chromatids begin to migrate toward the opposite poles of the cell.

• Telophase. During telophase, the chromosomes at either end of the cell cluster begin to cluster together, which facilitates the formation of a new nuclear membrane.

• This also is when cytokinesis occurs, leading to two separate cells. One way to identify that telophase has begun is by looking for the formation of the cell plate, the new cell wall forming between the two cells

ProphaseProphase• Prophase. During

prophase, the chromosomes supercoil and the fibers of the spindle apparatus begin to form between centrosomes located at the pole of the cells. The nuclear membrane also disintegrates at this time, freeing the chromosomes into the surrounding cytoplasm.

Prometaphase (Late Prophase)Prometaphase (Late Prophase)

• Prometaphase. During prometaphase, some of the fibers attach to the centromere of each pair of sister chromatids and they begin to move toward the center of the cell.

MetaphaseMetaphase

• Metaphase. At metaphase the chromosomes have come to rest along the center plane of the cell.

AnaphaseAnaphase

• Anaphase. During anaphase, the centromeres split and the sister chromatids begin to migrate toward the opposite poles of the cell.

Early Anaphase

                                                                 

             Late Anaphase

TelophaseTelophase

• Telophase. During telophase, the chromosomes at either end of the cell cluster begin to cluster together, which facilitates the formation of a new nuclear membrane.

Cytokinesis / Daughter CellCytokinesis / Daughter Cell

• cytokinesis occurs, leading to two separate cells. One way to identify that telophase has begun is by looking for the formation of the cell plate, the new cell wall forming between the two cells

Mitosis: Post-Mitosis Daughter Cells

                                                                                                                                              

                                         

Count the number of cells in each stage

Stage Percent time in each stage

Interphase

Prophase

Prometaphase

Metaphase

Ananphase

Telophase

Cytokinesis

Number of cells in each stage divided the total number of cell counted times 100 = percent time spent in each stage.

Multiple the percent time 24. That will give you the number pie sections to fill in.

1/24 of the pie

Time for MitosisTime for Mitosis

InterphaseProphasePrometaphaseMetaphaseAnaphaseTelophaseCytokinesis

Time for MitosisTime for Mitosis