Chapter 8 Cell Reproduction http://biofinity.org/images/Cell%20Division%20Micrograph.jpg

Section 1 Vocabulary Pretest Cells with one set of chromosomes Cells with two sets of chromosomes Rod-shaped structures made of DNA and proteins Proteins found in DNA X and Y chromosomes A chromosome other than a sex chromosome All chromosomes visible in a cell Matching chromosomes Copied half of a chromosome Holds chromatids together DNA during interphase Chromosome Histone Chromatid Centromere Chromatin Sex Chromosome Autosome Homologous Chromosome Karyotype Diploid Haploid

Answer Key Chromosome C Histone D Chromatid I Centromere J Chromatin K Sex Chromosome E Autosome F Homologous Chromosome H Karyotype G Diploid B Haploid A

Why Cells Divide Growth and repair Creation of gametes (Sex Cells) Method of reproduction in unicellular organisms http://stealthisknowledge.com/Pictures/images-mesoblast_cell_division_still.jpg

Chromatin While cells are growing, their DNA appears as long, stringy chromatin material. When cells are ready to divide, the chromatin condenses to form chromosomes. http://kmarsh2.umwblogs.org/files/2008/10/mitosis_cartoon_1.jpg

Chromosomes Chromosomes —DNA wrapped around proteins to form an X-shaped structure Histones —proteins that DNA wraps around Sections of chromosomes are called genes http://www.youtube.co m/watch?v=9kQpYdC nU14 (go to real player video folder on desktop: “How DNA is packaged”) Histones http://activity.ntsec.gov.tw/lifeworld/english/content/images/en_gene_c5.jpg

Chromosome Structure Each chromosome is made of two identical halves called sister chromatids held together at a point called a centromere. The sister chromatids are the result of DNA copying itself. They are called double stranded and will need to separate before the cell divides. http://www.biologycorner.com/resources/chromosome-labeled.gif

Chromosome Numbers Humans have 46 chromosomes in the nucleus of every cell Two are the sex chromosomes (X and Y) XX = female XY = male The other 44 are called autosomes They occur in matching pairs Called homologous chromosome pairs One chromosome in each pair comes from mom and the other comes from dad

Karyotypes A karyotype is a photograph of the matching pairs of chromosomes http://www.youtube.com/watch?v=V8sNC9Cdv0E&feature=related (go to real player video folder on desktop: “What is a Chromosome?”) http://www.mathemagic.org/MOBM/images/karyotype.jpg

Diploid vs Haploid Diploid cells contain the full set of chromosomes (all 46) All body cells are diploid Haploid cells contain half the number of chromosomes (23) One from each homologous pair Sperm and egg cells are haploid

Section 2 Vocabulary Pretest Binary fission Mitosis Asexual reproduction Meiosis Gametes Interphase Cytokinesis Prophase Spindle fiber Metaphase Anaphase Telophase Cell plate Division of cell’s cytoplasm Division of cell’s nucleus Reproductive cells Division of a prokaryotic cell Pull chromatids apart Chromosomes line up in middle of the cell Chromatids separate Two new nuclei form Production of offspring from one parent Time between cell divisions Results in the formation of gametes First phase of mitosis Forms between two new plant cells

Answer Key Binary fission D Mitosis B Asexual reproduction I Meiosis K Gametes C Interphase J Cytokinesis A Prophase L Spindle fiber E Metaphase F Anaphase G Telophase H Cell plate M

Cell Division How many new cells do you make every day? http://www.youtube.com/watch?v=Q6ucKWIIFmg (go to real player video folder on desktop: “Cell Division and the Cell Cycle”) How many new cells do you make every day? About 2 trillion (25 million cells per second) Cells reproduce asexually (one parent) One cell becomes two The process is different in prokaryotes and eukaryotes

Cell Division in Prokaryotes Prokaryotes reproduce by binary fission DNA is circular (no chromosomes) DNA copies itself Cell divides--- Simple 

Cell Division in Eukaryotes Eukaryotes use two types of cell division Mitosis —produces body cells Meiosis —produces gamete cells Both mitosis and meiosis happen in stages http://ghr.nlm.nih.gov/handbook/illustrations/mitosismeiosis.jpg

The Cell Cycle Mitosis is part of the Cell Cycle Three stages in the Cell Cycle: Interphase —period of growth, development and DNA replication Mitosis —division of the nucleus Cytokinesis —division of the cytoplasm http://www.youtube.com/ watch?v=lf9rcqifx34&feat ure=related (go to real player video folder on desktop: “Cell cycle” ) http://faculty.capebretonu.ca/cglogowski/BIOL%20101%20IMAGES/CellCycle_L.jpg

Interphase Cells spend most of their time in interphase Three phases G1—first growth phase (Cells grow to full size) S—DNA synthesis (copied) G2—second growth phase (prepares to divide) http://imcurious.wikispaces.com/file/view/cell_cycle.jpg/114427989/cell_cycle.jpg

Some cells exit the cycle after the G1 phase and enter the G0 phase Some cells exit the cycle after the G1 phase and enter the G0 phase. These cells no longer divide. Muscle cells Nerve cells

Mitosis Mitosis (division of nucleus) is divided into four stages: Prophase DNA condenses into chromosomes Nuclear membrane disappears Centrioles and spindle fibers appear Metaphase Chromosomes line up in the middle of the cell Anaphase Sister chromatids separate and move toward poles Telophase Chromosomes uncoil back into chromatin Nuclear membrane forms around each set of chromosomes

Stages of Mitosis Interphase Prophase Metaphase Anaphase Telophase http://www.clt.astate.edu/mhuss/mitosis1.jpg

Cytokinesis The final stage of the cell cycle is cytokinesis (dividing the cytoplasm) In animal cells, cytokinesis begins with a pinching in of the membrane forming a cleavage furrow. In plant cells, cytokinesis begins with the formation of a cell plate. End result is two identical diploid daughter cells http://www.uic.edu/classes/bios/bios100/lectf03am/cleavage.jpg http://www.vcbio.science.ru.nl/images/cellcycle/mito_solanum_cellplate.jpg

Meiosis Meiosis produces gamete cells (sperm and egg cells) Gamete cells are haploid (half the number of chromosomes) Full number of chromosomes is restored during fertilization. A cell passes through interphase and copies its DNA. The cell then divides twice resulting in 4 haploid gamete cells.

Meiosis is also divided into stages: Prophase I Chromosomes form and find their homologous match This is called synapsis (pairing of homologous chromosomes) Each pair of homologous chromosomes is called a tetrad. Crossing over can occur in each tetrad resulting in a genetic recombination of genes. http://www.biologycorner.com/resources/crossingover.jpg

Telophase I and Cytokinesis I Metaphase I Matching pairs of chromosomes (tetrads) line up in the middle of the cell and attach to spindle fibers. Anaphase I Homologous chromosomes separate and move to the poles (independent assortment) Telophase I and Cytokinesis I Nucleus and Cell both divide for the first time. This reduces the number of chromosomes to one half. This is called a reduction division. However, the chromosomes are still double stranded.

Telophase II and Cytokinesis II Prophase II Spindle fibers reappear Metaphase II Chromosomes line up in the middle of the cell and attach to spindle fibers Anaphase II Chromatids split and move to poles Telophase II and Cytokinesis II Nucleus and cell divide for the second time This is essentially a mitotic division. 4 haploid gamete cells are produced. They have half the number of single stranded chromosomes.

(go to real player video folder on desktop: “Meiosis Sq. Dance”) http://www.phschool.com/science/biology_place/labbench/lab3/images/stages2.gif

Meiosis occurs in the testes and the ovaries Spermatogenesis —production of 4 mature sperm cells. Oogenesis —production of 1 mature egg cell and 3 smaller polar bodies that degenerate. http://www.biologycorner.com/resources/oogenesis.jpg

Fertilization Fertilization —union of sperm and egg cell. Sexual reproduction, involving the production of sperm and egg cells by meiosis followed by fertilization, ensures genetic variation in all offspring. http://biology.ucsd.edu/classes/bimm110.SP07/images/fertilization2.jpg