• Get fill-in the blank notes from the front and your spiral.

• I EXPECT FOR ALL STUDENTS TO BE IN THEIR CHAIRS WHEN THE BELL RINGS!

The Cell Cycle

Interphase, Mitosis and Cytokinesis

Cell Reproduction- Intro Infromation

• Recall that the cell theory states that all cells come from preexisting cells.

• Cellular division is the process by which new cells are produced from one cell.

• This results in two cells that are identical to the original, parent cell.

• Right now, as you are reading this page, many of the cells in your body are growing, dividing, and dying.

• Old skin cells are being shed and replaced, cuts and bruises are healing.

• Worn-out tissues are repaired or replaced by newly produced cells.

Discovery of Chromosomes• Early biologists observed that just before

cellular division, several short, stringy structures suddenly appeared in the nucleus.

• Scientists also noticed that these structures seemed to vanish soon after division of the cell.

• These structures arechromosomes.

• Chromosomes are the carriers of the genetic material (DNA) that is copied through DNA replication so that each new cell has the correct genetic material in it.

Anatomy of a Chromosome

• For most of a cell’s lifetime, chromosomes exist as chromatin, long strands of DNA wrapped around proteins called histones.

• Under a microscope, chromatin looks like beads on a string.

Anatomy of a Chromosome• An unduplicated

chromosome is called a chromatid.

• When two identical chromatids are together (sister chromatids), this is called a duplicated chromosome.

• These sister chromatids are held together by a centromere

• In the body cells of animals and most plants, chromosomes occur in pairs. With the sister chromatids together.

• One chromosome in each pair came from the male parent, and the other came from the female parent.

• Humans have 46 chromosomes or 23 pairs.

• The 23rd pair are our sex chromosomes that make you male or female.

• Cells with two of each kind of chromosome are called diploid cells.

• The prefix dipl- means double• These are said to contain a diploid, or 2n,

number of chromosomes.• “n” stands for the number of duplicated

chromosomes. • This number multiplied by the 2 =the total

number of chromosomes for the cell.

• Organisms produce gametes or reproductive cells.– Ex. Humans produce gamete cells which are eggs for

females and sperm for males.

• These cells contain one of each kind of chromosome and are called haploid cells said to contain a haploid, or n, number of chromosomes.

• The prefix hapl- means single• Look at table 10.1 in your book on p. 265.

• This process of making gametes or reproductive cells is called meiosis.

• We will talk in detail about meiosis later.• For now you just need to understand the

following:– Our body cells (non-reproductive cells) are diploid

cells– Our egg and sperm (reproductive cells) are

haploid cells

Cell Cycle

• During the cell cycle, a cell grows, prepares for division, and divides to form 2 daughter cells, each of which then begins the cycle again.

• There are three main parts to the cell cycle.1. Interphase

a. G1, S, G2

2. Mitosisa. Prophase, Metaphase, Anaphase and Telophase

3. Cytokinesis

1. Interphase

• Interphase – Most of the cells life is spent in interphase.– G1 (Gap 1)=• Rapid growth and metabolic activity• Check point to make sure the conditions are correct to

support DNA replication– S (Synthesis)=DNA replicates– G2 (Gap 2)=• Cell prepares to divide• Second check point where the cell makes sure that the

DNA and other cell parts were replicated correctly.

2. Mitosis

• The division of somatic or regular cells.• Its divided into 4 phases.– PMAT• Prophase (prefix Pro- means 1st)• Metaphase (prefix Meta- means middle)• Anaphase (prefix Ana- means opposite)• Telophase (prefix Telo- means end)

Prophase

• First stage • Chromatin condenses

into chromosomes• Centrioles separate and

spindle fibers begin to form.

• Nuclear membrane breaks down

Metaphase

• Second Phase of Mitosis• Chromosomes line up in

the middle of the cell.• Each chromosome is

connected to a spindle fiber.

Anaphase

• Third Phase of Mitosis• The sister chromatids

separate into individual chromosomes and move apart to opposite ends of the cell.

Telophase

• The end or Final Stage of Mitosis

• Chromosomes gathered at opposite ends of the cell and lose their distinct shapes

• Two new nuclear membranes have formed.

3. Cytokinesis

• The cytoplasm pinches in half.

• Each daughter cell has an identical set of duplicate chromosomes