MITOSIS AND THE CELL CYCLE

Honors BiologySpring 2013

Warm-Up

With your neighbor, discuss the following: What does “The Cell Cycle” refer to? What are the main stages?

Essential Question

What are the stages of cell of the cell cycle?

Cell Reproduction Why reproduce? Why not just get larger?

Size Limitations

A. Cell Sizesmost cells are between 2 and 200 μm in diameter

B. Diffusion limits cell sizeC. DNA limits cell sizeD. Surface Area to Volume Ratio limits cell

size

Cell Reproduction Overview

A. Overview of Reproduction1. A characteristic of all living things2. One cell - parent cell - divides and forms new cells called the daughter cells3. Reproduction of the organism depends on the reproduction of the cell

a. unicellular organismsb. multicellular organisms

Cell Reproduction Overview

A. Overview of Reproduction4. When a cell reaches a certain size, it divides into daughter cells which are similar in structure to the parent cell5. Organisms reproduce in 2 basic ways

a. asexual reproductionb. sexual reproduction

Cell Reproduction Overview

B. Chromosomes1. Chromosomes are the carriers of the genetic material

made of sections of DNA known as genes2. become visible right before mitosis 3. # of chromosomes is characteristic of a species4. cells contain the diploid number of chromosomes

Chromosomes

Structural review Chromosomes are

composed of 2 identical sister chromatids attached by a centromere

Near the centromere is a kinetochore which is important for attaching the chromosome to the spindle during prophase

Diploid vs. Haploid

Diploid- a cell with two of each kind of chromosome; 2n; complete set

Haploid- cell with one of each kind of chromosome; n; ½ set

In mitosis & cytokinesis, 1 diploid cell splits into 2 diploid daughter cells

Haploid vs. Diploid

• human hapliod number?

23• human diploid number?

46

• most all human cells are diploid,

46 chromosomes

Cell Reproduction Overview

C. Cell Cycle1. The sequence of growth and division of a cell2. Two general periods a. growth – interphase

b. division - mitosis & cytokinesis

The Cell Cycle

The Cell Cycle

The pattern of growth, DNA duplication, and cell division that occurs in eukaryotic cells

4 main phases Gap 1 (G1): interphase Synthesis (S): interphase Gap 2 (G2): interphase Mitosis (M): mitosis and cytokinesis

Cell Division: Interphase G1:Cell caries out

normal functions and grows

S: DNA is copied (2 sets)

G2: Cell caries out normal functions and grows

A cell spends most of its time in Interphase (90%)

Genetic material is chromatin

Cell Division: Mitosis

Phases of Mitosis - cell division of a eukaryotic somatic cell1. Prophase2. Metaphase3. Anaphase4. Telophase5. Cytokinesis

Mitosis: Prophase

Nuclear envelope & nucleolus disappear (prometaphase)

Chromatin condenses into chromosomes

Centrioles move to opposite ends of cells (animals)

Spindle (microtubules) begins to form

Longest part of mitosis

Mitosis: Metaphase

Doubled chromosomes become attached to the spindle by their kinetochores/ centromeres (prometaphase)

The chromosomes are pulled by the spindle and they begin to line up along the equator of the cell

Mitosis: Anaphase

Centromeres split apart

Sister chromatids pull away from each other because of the shortening of the microtubules in the spindle fibers

Each chromatid is now considered a full-fledged chromosome

Mitosis: Telophase

Chromatids reach opposite ends of the cell

Chromosomes unwind back into chromatin

Spindle breaks down

Nuclear membrane and nucleolus reappear

Cytokinesis

Division of the cytoplasm

Usually begins before Telophase is complete

Each daughter cells leaves cytokinesis to start interphase again

Differences in plant and animal cells

Cleavage furrow

Cell plate

Additional Information

Result of mitosis= 2 daughter cells that are genetically identical to the 1 original cell

Rate of mitosis varies on the cell and organism

Mitosis is controlled by enzymes

Think About It!

How does mitosis differ in plant and animal cells?

Cytokinesis in Plants

• plant cells do not have use a cleavage furrow to separate

• plants use a cell plate to split parent cell in two• the cell plate becomes the cell wall of the two

daughter cells

Think About It!

Why would control of cell division be important?

Asexual Reproduction

Prokaryotes have a single circular chromosome

B. Binary fission

Binary Fisson