Chapter 8 NotesChapter 8 Notes

MitosisMitosis Cells must divideCells must divide: :

1.1.to keep the to keep the surface to volume ratio surface to volume ratio manageablemanageable

2.2.because if cells get too large, they because if cells get too large, they can not eliminate wastes and bring can not eliminate wastes and bring in proper nutrition.in proper nutrition.

Diploid – 2 sets of chromosomes Diploid – 2 sets of chromosomes (ex. 46 in human body cells) – 2n(ex. 46 in human body cells) – 2n

Haploid – 1 set of chromosomes Haploid – 1 set of chromosomes (ex. 23 in human sex cells) - n(ex. 23 in human sex cells) - n

Chromatin and Chromatin and ChromosomesChromosomes

Chromatin is the thin, threadlike DNA found when Chromatin is the thin, threadlike DNA found when the cell is not dividing.the cell is not dividing.

Chromosomes are the thick coiled visible form of Chromosomes are the thick coiled visible form of DNA found during cell division.DNA found during cell division.

ChromosomeChromosome

DNADNA In In prokaryotic cellsprokaryotic cells, the , the circularcircular

chromosomechromosome (DNA) floats in the (DNA) floats in the cytoplasm.cytoplasm.

In eukaryotic cells, sets of In eukaryotic cells, sets of chromosomes in different lengths chromosomes in different lengths (DNA) are found in the nucleus of (DNA) are found in the nucleus of the cell.the cell.

Cell CycleCell Cycle During the cell cycle, a cell grows, During the cell cycle, a cell grows,

replicates (copies) all of its DNA, and replicates (copies) all of its DNA, and divides into two daughter cells, which divides into two daughter cells, which each receives an exact copy of the each receives an exact copy of the parent cell’s DNA.parent cell’s DNA.

In humans, parent cells have 46 In humans, parent cells have 46 chromosomes, so each daughter cell will chromosomes, so each daughter cell will have 46 chromosomes.have 46 chromosomes.

Cell CycleCell Cycle There are 2 main parts of the cell cycle:There are 2 main parts of the cell cycle:

1. interphase1. interphase 22. cell division (mitosis and . cell division (mitosis and

cytokinesis cytokinesis Interphase Interphase is the part of the cell cycle is the part of the cell cycle

in which the cell is growing in which the cell is growing and carrying and carrying out its function. This is when the cell is out its function. This is when the cell is doing its jobdoing its job

Cell CycleCell Cycle There are 2 main parts of the cell cycle:There are 2 main parts of the cell cycle:

1. interphase1. interphase 22. cell division (mitosis and . cell division (mitosis and

cytokinesis cytokinesis Mitosis is the division of the nucleusMitosis is the division of the nucleus Cytokinesis is the division of the Cytokinesis is the division of the

cytoplasm. cytoplasm.

InterphaseInterphase

3 phases of interphase:3 phases of interphase:1. G1 – Cell growth1. G1 – Cell growth2. S – DNA replication2. S – DNA replication3. G2 – preparation for mitosis; 3. G2 – preparation for mitosis;

organelles are producedorganelles are producedG1-G1- S S G2G2MM C C

End part 1

Mitosis - ProphaseMitosis - Prophase

PROPHASE:PROPHASE: Chromatin condenses into chromosomesChromatin condenses into chromosomes Nuclear membrane is broken downNuclear membrane is broken down Spindle fibers formSpindle fibers form

Mitosis - MetaphaseMitosis - Metaphase

METAPHASE:METAPHASE: Chromosomes line up in the MIDDLE of Chromosomes line up in the MIDDLE of

the cell.the cell.

Mitosis - AnaphaseMitosis - Anaphase

ANAPHASE:ANAPHASE: The sister chromatids separate and move The sister chromatids separate and move

APART toward the opposite sides of the APART toward the opposite sides of the cell.cell.

Mitosis - TelophaseMitosis - Telophase

TELOPHASE:TELOPHASE: Chromosomes uncoil into chromatin. Chromosomes uncoil into chromatin. Two new nuclear membranes form.Two new nuclear membranes form. Opposite of prophase.Opposite of prophase.

CytokinesisCytokinesis

CYTOKINESIS:CYTOKINESIS: The cell membrane and cytoplasm divideThe cell membrane and cytoplasm divide In plant cells, a cell plate is formed, which In plant cells, a cell plate is formed, which

turns into a new cell wall.turns into a new cell wall. Animal cells pinch in half.Animal cells pinch in half. Result of mitosis: 2 daughter cells that Result of mitosis: 2 daughter cells that

are exactly like the parent cell are exactly like the parent cell

A karyotype shows the number of A karyotype shows the number of chromosomes and whether it is a chromosomes and whether it is a boy or girl.boy or girl.

Gamete – sex (reproductive) cell – Gamete – sex (reproductive) cell – egg or sperm (or pollen) – haploidegg or sperm (or pollen) – haploid

Somatic cell – body cell - diploidSomatic cell – body cell - diploid

In meiosis, crossing over takes In meiosis, crossing over takes place when homologous place when homologous chromosomes exchange segments chromosomes exchange segments of DNA.of DNA.