11-4 Meiosis  Understand that homologous chromosomes separate randomly during meiosis to produce haploid gametes. COPYRIGHT PEARSON PRENTICE HALL MT: Sexual Reproduction

11-4 Meiosis CELL DIVISION: MEIOSIS & SEXUAL REPRODUCTION Images: Peter, Lois & Stewie, The Family GuyThe Family GuyFrom the Virtual Cell Biology Classroom on ScienceProfOnline.comVirtual Cell Biology ClassroomScienceProfOnline.com

11-4 Meiosis WHAT IS HAPPENING HERE? COPYRIGHT PEARSON PRENTICE HALL

11-4 Meiosis FERTILIZATION COPYRIGHT PEARSON PRENTICE HALL = when a male and female gamete join

11-4 Meiosis CHROMOSOME #  Most organisms are diploid and thus want an offspring that is also diploid  So, each gamete has to be haploid so when they join they create a diploid organism COPYRIGHT PEARSON PRENTICE HALL mitosis meiosis

11-4 Meiosis FIND CHROMOSOME #  DIPLOID #  Human 46 chromosomes  Dog 78 chromosomes  Carrot 18 chromosomes  Goldfish 94 chromosomes  Wheat 42 chromosomes  Tobacco 48 chromosomes COPYRIGHT PEARSON PRENTICE HALL  HAPLOID #  Human __ chromosomes  Dog __ chromosomes  Carrot __ chromosomes  Goldfish __ chromosomes  Wheat __ chromosomes  Tobacco __ chromosomes

11-4 Meiosis haploid (n) + haploid (n) = diploid (2n) OR Female gamete + male gamete = offspring somatic cell OR ½ + ½ = 1 COPYRIGHT PEARSON PRENTICE HALL

11-4 Meiosis COPYRIGHT PEARSON PRENTICE HALL CHROMOSOME NUMBER  These two sets of chromosomes are homologous.  One chromosome from mom and one chromosome from dad.

11-4 Meiosis HOMOLOGOUS CHROMOSOMES Pair Pair of chromosomes that contain the same alleles for a trait EX: chromosome with eye color allele from mom is homologous to chromosome with eye color allele from dad Mom (1,3) Dad (2,4)

11-4 Meiosis WHICH PAIR UP TO MAKE HOMOLOGOUS CHROMOSOMES? How many pairs of homologous chromosomes are shown? How many chromosomes are shown? Pink with pink; yellow with yellow; blue with blue 3 6

11-4 Meiosis What happens during the process of meiosis? COPYRIGHT PEARSON PRENTICE HALL making of non-identical haploid gametes

11-4 Meiosis PHASES OF MEIOSIS I  Meiosis I COPYRIGHT PEARSON PRENTICE HALL Prophase I Metaphase I Anaphase I Telophase I and Cytokinesis Interphase I

11-4 Meiosis INTERPHASE 1  DNA copies itself COPYRIGHT PEARSON PRENTICE HALL nucleus centrioles

11-4 Meiosis PROPHASE I  Nuclear membrane disappears.  Homologous chromosomes pair up to form a tetrad.  Tetrad = 4 sister chromatids  Crossing over occurs COPYRIGHT PEARSON PRENTICE HALL

11-4 Meiosis CROSSING OVER  When homologous chromosomes form tetrads in meiosis I, they exchange portions of their chromatids in a process called crossing over.  Crossing-over produces new combinations of alleles. COPYRIGHT PEARSON PRENTICE HALL Does crossing over always occur at the same allele? NO! It is random

11-4 Meiosis METAPHASE 1  Homologous chromosomes line up in middle of cell  Spindle fibers attach to the chromosomes’ centromeres. COPYRIGHT PEARSON PRENTICE HALL

11-4 Meiosis ANAPHASE 1  The fibers pull the homologous chromosomes toward opposite ends of the cell. COPYRIGHT PEARSON PRENTICE HALL

11-4 Meiosis TELOPHASE 1  The cell separates into two cells  Nuclear membranes reappear COPYRIGHT PEARSON PRENTICE HALL

11-4 Meiosis PHASES OF MEIOSIS II  Meiosis II COPYRIGHT PEARSON PRENTICE HALL Telophase II and Cytokinesis Prophase II Metaphase II Anaphase II Telophase I and Cytokinesis I

11-4 Meiosis INTERPHASE II  NOPE!  Cells DO NOT need to grow or copy DNA since they are trying to get smaller COPYRIGHT PEARSON PRENTICE HALL

11-4 Meiosis PROPHASE II  Nuclear membrane disappears. COPYRIGHT PEARSON PRENTICE HALL

11-4 Meiosis METAPHASE II  Individual chromosomes line up in the middle of cell. COPYRIGHT PEARSON PRENTICE HALL

11-4 Meiosis ANAPHASE II  The sister chromatids separate and move toward opposite ends of the cell. COPYRIGHT PEARSON PRENTICE HALL

11-4 Meiosis TELOPHASE II  Meiosis II results in four non- identical haploid cells. COPYRIGHT PEARSON PRENTICE HALL

11-4 Meiosis GAMETE FORMATION  In male animals, meiosis results in four equal- sized gametes called sperm. COPYRIGHT PEARSON PRENTICE HALL

11-4 Meiosis GAMETE FORMATION  In many female animals, only one egg results from meiosis. The other three cells, called polar bodies, are usually not involved in reproduction. COPYRIGHT PEARSON PRENTICE HALL

11-4 Meiosis Image: Meiosis diagram, Marek KultysMeiosis diagram From the Virtual Cell Biology Classroom on ScienceProfOnline.comVirtual Cell Biology ClassroomScienceProfOnline.com View Meiosis Animation

11-4 Meiosis Image: Mitosis diagram & Meiosis diagram, Marek KultysMitosis diagramMeiosis diagram From the Virtual Cell Biology Classroom on ScienceProfOnline.comVirtual Cell Biology ClassroomScienceProfOnline.com

11-4 Meiosis MITOSIS VS. MEIOSIS  2n  Clone  Same genetic information in parent cell and daughter cell.  Give me another one just like the other one VIDEO  1n  Daughter cells different from parent cell and from each other.  Daughter cells have ½ the number of chromosomes as somatic cell.  Shuffling the genes (Mix it up!) From the Virtual Cell Biology Classroom on ScienceProfOnline.comVirtual Cell Biology ClassroomScienceProfOnline.com

11-4 Meiosis WEBSITES TO CHECK OUT COPYRIGHT PEARSON PRENTICE HALL hill.com/sites/ /student_view0/chapter28/ani mation__how_meiosis_works.htmlhttp://highered.mcgraw- hill.com/sites/ /student_view0/chapter28/ani mation__how_meiosis_works.html 4.