# Chapter 10 Cell Division Ch. 10: Section 1

Chapter 10 Cell Division Ch. 10: Section 1 I. Limits to Cell Growth/Size A. DNA Overload If a cell grows too large, its DNA could no longer serve the needs of the entire cell B. Exchanging materials if a cell is too large, is struggles to move enough

nutrients & wastes throughout the cell and to the cell membrane II. Surface Area to Volume Ratio A. Surface Area = length x width x # of sides B. Volume = length x width x height C. Surface Area to Volume Ratio = SA/V D. Volume increases more rapidly than surface area, causing the ratio to decrease

E. 2 lane main street into a town will experience more traffic as town gets bigger, and it takes longer to get to center of town as size of town increases. II. Surface Area to Volume Ratio (cont) Calculations: All sides = All sides = All sides =

Cell Size: Surface Area (length x width x 6) Volume (length x width x height) Ratio of Surface Area to Volume

(SA/V) 1cm 2cm 3cm II. Surface Area to Volume Ratio (cont) Calculations:

All sides = All sides = All sides = Cell Size: 1cm 2cm 3cm Surface Area

(length x width x 6) 6 cm2 24 cm2 54 cm2 Volume (length x width x

height) 1 cm3 8 cm3 27 cm3 6/1 = 6:1

24/8 = 3:1 54?27 = 2:1 Ratio of Surface Area to Volume (SA/V)

Ch. 10: Section 2 I. Why cells divide/reproduce A. Growth new cells are needed to grow tissues and organs B. Replacement & Renewal old/damaged cells die & are replaced with new C. Reproduction 1. 2.

unicellular organisms divide to make new organisms multicellular organisms divide cells to make sex cells (gametes). II. Chromosome Structure A. Gene DNA is a large molecule broken down into hereditary units called genes

DNA is organized & packaged into chromosomes during cell division B. Chromosome DNA wound or coiled tightly around proteins (histones) Prokaryote Chromosome a single, circular

loop of DNA Eukaryote Chromosome many linear DNA molecules packaged into chromosomes C. Structure fully condensed, duplicated

A chromosome is made of 2 identical halves. Each half is called a chromatid. A centromere holds 2 chromatids together to make a chromosome. DNA is packaged as a chromosome only during cell division, after it has been copied. When a cell is not dividing, its DNA is packaged more loosely as chromatin.

Cell Cycle Video III. Chromosome #s - each species has a different number of chromosomes A. Sex Chromosomes and X or Y chromosome 1. They determine the sex of the individual

2. Female = XX Male = XY B. Autosomes all remaining chromosomes 1. In humans: 44 autosomes + 2 sex chromosomes = 46 total chromosomes 2. The 44 autosomes in a human are actually 22 pairs. An individual gets a copy of each chromosomes from each parent.

C. Homologous Chromosomes a pair of chromosomes 1. A human has 22 homologous chromosome pairs 2. A homologous pair are the same size, shape, and contain the same types of genes for the same traits. Each chromosome can have different specific genes than its

homologous pair D. Diploid Cells 1. Are cells having all homologous pairs and 2 sex chromosomes 2. All cells except gametes (gametes = sex cells: egg and sperm cells) 3. Diploid cell are abbreviated as 2n, where n = # of 1 set of chromosomes. 4. Also called body cell, or somatic cells.

5. The chromosomes of diploid cells can be arranged and studied using karyotypes. E. Haploid Cells 1. Cells that contain only 1 chromosome from the pair of homologous chromosomes and 1 sex chromosome. 2. Haploid cells are abbreviated as n. 3. Haploid cells are gametes.

Chromosome # Example A male human has 46 total chromosomes. (A chromosome is made of 2 chromatids, duplicated copies of the same DNA molecule) # of autosomes = # of sex chromosomes = The sex chromosomes are # of homologous pairs =

Diploid # (2n) = Haploid # (n) = IV. Eukaryote Cell Cycle A. Cell Cycle repeating events of growth and division during the life of a cell B. Interphase time when cell is not dividing 1. G1 Phase cells grows rapidly as it makes more organelles

2. S Phase DNA/chromosome is copied 3. G2 Phase cell continues to grow and makes organelles for cell division 4. G0 Phase when cell doesnt divide (instead of G1, S, & G2 Phases) C. Mitosis division of the nucleus (DNA) 1. Prophase 1st step DNA is packaged into chromosomes Nucleolus and nuclear membrane

break apart Centrioles move to opposite ends of the cell 2. Metaphase 2nd step Spindle fibers coming from the centrioles attach to the centromeres of the chromosomes Chromosomes line up in the middle of the cell

3. Anaphase 3rd step Spindle fibers pull chromatids apart at the centromere Each chromatid is now considered a chromosome! 4. Telophase 4th (last) step Spindle fibers disappear Nuclear envelope reforms around

each set of chromosomes D. Cytokinesis 1. Begins during telophase. 2. Is the division of the cell/cytoplasm. Animal cells: cell membrane pinches inward making a cleavage furrow. This continues until 2 cells are formed. Plant Cells: a cell plate forms between the 2 sets of chromosomes.

***Mitosis happens in somatic cells and makes 2 diploid cells! Mitosis in a Plant Cell Mitosis in an Animal Cell Mitosis Video E. Controls on Cell Division

1. Physical contact Cells tend to divide until a space has been filled. Once that space has been filled, or the cells contact each other, they stop dividing. 2. Cell Cycle Regulators Cyclin protein that regulates the cell cycle

High levels of cyclin = cell division Low levels of cyclin = Interphase F. Uncontrolled Cell Growth 1. Cancer cells lose the ability to control cell divison/growth 2. Cancer cells do not respond to the signals that regulate the growth of most other cells. 3. As a result, they form masses of cells,

tumors, that can damage the surrounding tissues. Section 11-4: Meiosis Meiosis cell division that halves the number of chromosomes in new cells, making haploid cells *Recall, haploid cells in human are egg/sperm cells, called gametes, and contain 23 chromosomes.

Stages of Meiosis I. Interphase A. cells go through G1, S, and G2 phases; B. DNA is copied and cells grow larger. II. Meiosis I A. Prophase I 1.

DNA is coiled into chromosomes & nucleus breaks down 2. Centrioles move to ends of cell; spindle fibers appear 3. Chromosomes pair up (in homologous pairs) and twist together. Portions of a chromatid can break off and reattach to the identical chromatid on its homologous chromosome = crossing over

Prophase I and Crossing Over B. Metaphase I 1. Homologous chromosomes line up randomly in the center of the cell 2. Spindle fibers attach to the centromeres C. Anaphase I 1. Spindle fibers pull homologous chromosomes apart.

2. The direction the chromosomes are pulled is random = independent assortment D. Telophase I 1. Chromosomes move to opposite ends of the cell 2. Cytokinesis occurs **Meiosis I results in 2 new haploid cells III. Meiosis II

Begins immediately after Meiosis I. Both cells from Meiosis I go through Meiosis II. DNA is not copied this time!!!!!!! A. Prophase II spindle fibers reform, centrioles move to opposite ends of cell B. Metaphase II single chromosomes line up in the middle of the cell C. Anaphase II spindle fibers attach at

centromeres and pull chromatids apart D. Telophase II chromatids move to opposite ends, and nucleus forms around them and cytokinesis occurs **Meiosis II results in 4 new Haploid cells. Stages of Meiosis II IV. Meiosis Forms Gametes A. The 4 haploid cells produced in Meiosis

are gametes (sex cells = egg/sperm) B. Spermatogenesis production of sperm cells C. Oogenesis production of mature egg cells or ova (singular = ovum) V. Genetic Variation in Meiosis A. Crossing Over switching of DNA between chromatids of homologous pairs; occurs during prophase I

B. Independent Assortment each homologous pair is separated independent of how the other pairs are separated. C. Random Fertilization of the 4 gametes produced in meiosis, any one can fertilize (join) with another gamete

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