Chapter 8: Cell Division and Growth

Chapter 10 Cell Growth and Division

I. Cell GrowthA. When cells are NOT dividing, DNA is found in the nucleus in the form of uncoiled chromatin.1. What does this look like in the cell? A mass of genetic material that is spread out; a bowl of spaghetti.

2. When the cell is getting ready to divide, chromosomes form as the DNA wraps around histones.

I. Cell GrowthB. Chromosomes carriers of genetic information that is copied and passed to new cells1. Gene section of DNA that controls production of a protein; found on a chromosome

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I. Cell Growth2. Structure of Chromosomesa. Each chromosome consists of two identical halves. These halves are known as sister chromatids.b. Joining the pair of chromatids together is a centromere. This holds them together until they separate at cell division.

c. What does this look like in the cell?I. Cell Growth

3. Chromosome Numbersa. Each organism has a characteristicnumber of chromosomes. - Fruit flies = 8 chromosomes (4 pair)- Adders Tongue Fern = 1, 262 chromosomes (631 pairs)- Humans = 46 chromosomes (23 pairs)

I. Cell Growth

I. Cell GrowthC. Two types of Chromosomes1. Sex Chromosomes determine the sex of an organism; humans have 2 of these chromosomes (1 pair)a. Male = XY, Female = XX

I. Cell Growth2. Autosomes the remaining body chromosomes; humans have 44 of these. They will travel in pairs, as homologous chromosomes.

I. Cell Growth3. This means you have 2 of every chromosome, they carry genes for the same traits, but they are NOT identical. a. Where do they come from? You receive 1 chromosome from each parent! b. Example: Chromosome 19 contains genes for hair color. Moms #19 could have the blonde hair gene and Dads #19 could the brown hair gene.

I. Cell Growth

D. Chromosomes in Each Cell1. Diploid a cell containing 2 copies of each chromosome (both chromosomes in the homologous pair)a. Abbreviated: 2Nb. Human example: skin cells, muscle cells (any BODY cell), 2N = 46I. Cell Growth2. Haploid a cell containing 1 copy of each chromosomea. Abbreviated: Nb. Human example: sperm and eggs cells (any SEX/gamete cell), N =23

I. Cell GrowthE. Cell Size Limits1. Organisms grow by producing more cells. a. Cell size is usually comparable between a young and old animal; the older animal just has more of them.

I. Cell Growth2. Why cant cells continually grow larger?a. DNA Overload it can no longer meet all the cells needs/demands

I. Cell Growth

b. Exchanging materials - Rate at which materials are exchanged depends on the cell membrane (surface area of the cell).- Rate at which materials are used (oxygen, water) or produced (waste) depends on the volume of the cell.I. Cell Growth

c. As the length of the cell increases, the volume increases faster than the surface area. d. It is hard for the cells to keep up with moving materials and wastes in and out, so the cell divides.I. Cell GrowthA. Cell division performed by prokaryotes is a simple process. Two identical cells are created from one cell through the process of binary fission.1. Steps of Binary Fissiona. Chromosome attached to inside of cell membrane makes a copy of itself.II. Cell Division

b. Cell begins to grow until it is about two times the size of parent cell.c. A new cell wall forms between the two chromosomes; cell splits into two new cells. II. Cell Division

B. Two Types of Cell Division in Eukaryotes1. Mitosis cell division that produces body cells identical to the original parent cell (diploid)a. Examples of cells that do this: skin, muscle, heart2. Meiosis cell division that produces gametes (sex cells) with half the number of chromosomes as the parent cell (haploid)a. Examples of cells that do this: sperm and egg; GAMETES ONLYII. Cell Division

C. Cell Cycle sequences of growth and division of the cell1. Three Steps of the Cell Cyclea. Interphase (most time spent here)b. Mitosisc. CytokinesisII. Cell DivisionHow long does it take for a cell to go through one cell cycle?

It all depends on the cell.

A human liver cell, for example, completes one cell cycle in about 22 hours, as shown in the graph. II. Cell DivisionD. Cell Cycle in Detail1. Interphase - time when the cell is NOT dividinga. Three Phases of Interphase- G1 - cell grows, makes organelles- S - DNA copied (synthesized)- G2 - cell makes centrioles; normal metabolism; preparing to divide

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2. Mitosis - dividing of the cells nucleusFOUR PHASES OF MITOSISa. Prophaseb. Metaphasec. Anaphased. TelophaseII. Cell Divisiona. Four Phase of Mitosis- Prophase - longest phase of mitosisChromatin coils into visible chromosomes (sister chromatids)Nuclear envelope/membrane starts to disappearSpindle fibers appear from centrioles (animal cells only)

II. Cell Division- Metaphase - shortest phase of mitosisSpindles attach and move chromosomes to line up along the equator (middle) of the cell

II. Cell Division- Anaphase - Chromosomes are pulled apart at the centromere by spindles and separated into sister chromatids

II. Cell Division- Telophase - Sister chromatids reach opposite poles (sides of the cell)Spindles disappearNuclear envelopes/membranes reappearCell begins to split into 2 new cells

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- Cytokinesis - dividing of the cells cytoplasm, forming two new cellsAnimal cells: 2 new cells are separated by the cytoplasm pinching in

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Plant cells: 2 new cells separated by a cell plate that helps form the cell wallsII. Cell Division- Cytokinesis -

II. Cell DivisionE. Meiosis1. Meiosis - Cell division that produces gametes with half the number of chromosomes as the parent cell (haploid)a. 2 separate cell divisions: meiosis I and meiosis II- Interphase and cytokinesis occur with both divisions

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b. Meiosis starts with 1 diploid cell and ends with 4 haploid cells; Each gamete has half the number of chromosomes as a diploid cell.

1 diploid cell with 4 chromosomes4 haploid cells with 2 chromosomes eachII. Cell Division

F. Steps of Meiosis1. MEIOSIS Ia. Prophase I - DNA coils into tetrads (pair of homologous chromosomes) Spindles appearNuclear envelope/membrane disappearsCrossing over occurs - DNA is swapped between chromosomes in a pair

II. Cell Divisionb. Metaphase I- Tetrads are moved by the spindles and line up along the middle/equator of the cell.

II. Cell Divisionc. Anaphase I -Tetrads pulled apart by the spindles and separated into chromosomesChromosomes begin moving to opposite ends of the cell

II. Cell Divisiond. Telophase I - Chromosomes reach opposite sides of the cellSpindle disappearsNuclear envelope/membrane reappearsCytokinesis occurs after this step, forming two new cells, which then go through interphase again

II. Cell Division Meiosis II--has 4 stages, PMAT IIEach stage--occurs just like the stages of mitosis

Prophase II

Metaphase II

Anaphase II

Telophase IIII. Cell Division2. MEIOSIS IIa. Prophase II - Spindle appear in each of the 2 new cellsNuclear envelopes/membranes disappears

II. Cell Divisionb. Metaphase II - Sister chromatids line up in the middle/equator of the cell.

II. Cell Divisionc. Anaphase II - Spindles split centromeres and sister chromatids separateChromatids start to move to opposite ends of the cell

II. Cell Divisiond. Telophase II - Sister chromatids (haploid) reach opposite ends of the cellSpindles disappear Nuclear envelopes/membranes appearCytokinesis follows this step forming four new cells

II. Cell DivisionG. Soooooooooooo, what happens after meiosis?1. Sexual Reproduction - production and combination of gametesa. Fertilization- fusion of male and female gametes to form zygoteZygote - diploid cell (2 of each chromosome)

http://video.sciencemag.org/VideoLab/2127025888001/1/medicineII. Cell DivisionComparison of Types of DivisionMitosisMeiosisOccurs in most body cellsOccurs only in sex cellsOne divisionTwo divisionsOne cell makes 2 diploid cellsOne cell makes 4 haploid cellsIdentical to the parentDifferent from parent