MEIOSIS 11-4 Making gametes… http://waynesword.palomar.edu/lmexer2a.htm Making gametes…

Interest Grabber 1. How many chromosomes would a sperm or an egg contain if either one resulted from the process of mitosis? 2. If a sperm containing 46 chromosomes fused with an egg containing 46 chromosomes, how many chromosomes would the resulting fertilized egg contain? Do you think this would create any problems in the developing embryo? 3. In order to produce a fertilized egg with the appropriate number of chromosomes (46), how many chromosomes should each sperm and egg have? 46 chromosomes 46 + 46 = 92; a developing embryo would not survive if it contained 92 chromosomes. Sperm and egg should each have 23 chromosomes.

Objectives Contrast the chromosome # of body cells and gametes Summarize the events of meiosis Contrast meiosis and mitosis

+ EGG SPERM  If egg and sperm had same number of http://www.angelbabygifts.com/ Image by Riedell Image by Riedell EGG + SPERM  If egg and sperm had same number of chromosomes as other body cells . . . baby would have too many chromosomes! http://www.acmecompany.com/stock_thumbnails/13217.forty-six_chromosomes.jpg

MEIOSIS is the way… to make cells with ½ the number of chromosomes for sexual reproduction http://waynesword.palomar.edu/lmexer2a.htm

Click the image to play the video segment 11A. Meiosis Overview Click the image to play the video segment 11A. Video 1

DIPLOID & HAPLOID HOMOLOGOUS CHROMOSOMES Most cells have 2 copies of each chromosome = ______________ (one from mom; one from dad) All BODY (___________) cells are diploid DIPLOID 2n HOMOLOGOUS CHROMOSOMES = SOMATIC

HOMOLOGOUS CHROMOSOMES SAME SIZE SAME SHAPE CARRY GENES for the SAME TRAITS BUT ______________! (Don’t have to have the SAME CHOICES) Image modified by Riedell NOT IDENTICAL http://sps.k12.ar.us/massengale/genetics%20tutorial.htm

DIPLOID & HAPLOID Some cells have only one copy of each chromosome = _____________ All sperm and egg cells are haploid HAPLOID 1n

MITOSIS REVIEW Makes ___ cells genetically _________ to parent cell & to each other Makes ___ cells Makes __________ Used by organisms to: increase size of organism, repair injuries, replace worn out cells 2 identical 2n SOMATIC (body) http://waynesword.palomar.edu/lmexer2a.htm

MEIOSIS 4 1n Gametes (sperm & eggs) sexual reproduction Makes ____ cells genetically different from parent cell & from each other Makes _____ cells Makes ______________ Used for ____________ 1n Gametes (sperm & eggs) sexual reproduction http://waynesword.palomar.edu/lmexer2a.htm

PREDICT THE OUTCOMES Unicorns have 40 chromosomes After Mitosis Two 2n cells each with 40 chromosomes After Meiosis Four 1n cells each with 20 Loch Ness Monsters have 50 chromosomes Two 2n cells each with 50 Four 1n cells each with 25

PREDICT THE OUTCOME You are studying a cell with 20 chromosomes, and it goes through a process that produces haploid cells. What is the process called? How many chromosomes would be in the new cells? How many cells would you now have?

WHAT MAKES MEIOSIS DIFFERENT ? SYNAPSIS & CROSSING OVER (PROPHASE I) SEGREGATION & INDEPENDENT ASSORTMENT (ANAPHASE I) 3. Skip INTERPHASE II (NO S) CELL DIVIDES TWICE, BUT… ONLY COPIES DNA ONCE

WHAT MAKES MEIOSIS DIFFERENT ? Homologous chromosomes pair up during ________________ = ______________ PROPHASE I SYNAPSIS This group of FOUR (4) chromatids is called a _________________ TETRAD Images modified from: http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif

WHAT MAKES MEIOSIS DIFFERENT? 1. Exchange of DNA between homologous pairs = _____________ during PROPHASE I CROSSING OVER Allows shuffling of genetic material http://www.emc.maricopa.edu/faculty/farabee/BIOBK/Crossover.gif

Click the image to play the video segment. 11E Crossing Over SEE CROSSING OVER ANIMATION Click the image to play the video segment. 11E Video 5

WHAT MAKES MEIOSIS DIFFERENT ? 2.Separation during ANAPHASE I SEGREGATION & INDEPENDENT ASSORTMENT Separates gene choices and allows shuffling of genetic material

Click the image to play the video segment 11D. Segregation of Chromosomes Click the image to play the video segment 11D. Video 4

SEGREGATION (Anaphase I)

SEGREGATION & CROSSING OVER together make even more combinations See an animation http://waynesword.palomar.edu/lmexer2a.htm

INDEPENDENT ASSORTMENT http://fig.cox.miami.edu/~cmallery/150/mitosis/c13x9independent-assortment.jpg

INDEPENDENT ASSORTMENT at ANAPHASE I Lots of different combinations are possible! This is why you don’t look exactly like your brothers and sisters even though you share the same parents!

http://www.tokyo-med.ac.jp/genet/anm/mimov.gi

WHAT MAKES MEIOSIS DIFFERENT ? Crossing over Segregation Independent assortment are ALL ways MEIOSIS results in =______________________________ So daughter cells are ______________ from parents and from each other GENETIC RECOMBINATION different

WHAT MAKES MEIOSIS DIFFERENT ? 3. Skip INTERPHASE II (No S) CELL DIVIDES TWICE, BUT … ONLY COPIES ITS DNA ONCE MITOSIS: G1 S G2 P M A T C        MEIOSIS: ( I ) G1 A T C S G2 P M        P M A T C ( II )    

Click the image to play the video segment 11B. & C Animal Cell Meiosis, Part 1 & Part 2 Click the image to play the video segment 11B. & C

MITOSIS vs MEIOSIS INTERPHASE INTERPHASE I http://www.pbs.org/wgbh/nova/baby/divi_flash.html SAME

MITOSIS vs MEIOSIS PROPHASE PROPHASE I http://www.pbs.org/wgbh/nova/baby/divi_flash.html Homologous pairs match up

MITOSIS vs MEIOSIS METAPHASE METAPHASE I http://www.pbs.org/wgbh/nova/baby/divi_flash.html Tetrads line up in middle

MITOSIS vs MEIOSIS ANAPHASE ANAPHASE I http://www.pbs.org/wgbh/nova/baby/divi_flash.html APART: Tetrad splits apart

MITOSIS vs MEIOSIS TELOPHASE TELOPHASE I http://www.pbs.org/wgbh/nova/baby/divi_flash.html SAME

MITOSIS vs MEIOSIS CYTOKINESIS CYTOKINESIS I http://www.pbs.org/wgbh/nova/baby/divi_flash.html SAME

MITOSIS vs MEIOSIS INTERPHASE II http://www.pbs.org/wgbh/nova/baby/divi_flash.html SKIP INTERPHASE II DNA NOT COPIED

MITOSIS vs MEIOSIS PROPHASE PROPHASE II http://www.pbs.org/wgbh/nova/baby/divi_flash.html SAME

MITOSIS vs MEIOSIS METAPHASE METAPHASE II http://www.pbs.org/wgbh/nova/baby/divi_flash.html SAME

MITOSIS vs MEIOSIS ANAPHASE ANAPHASE II http://www.pbs.org/wgbh/nova/baby/divi_flash.html Same

MITOSIS vs MEIOSIS TELOPHASE TELOPHASE II http://www.pbs.org/wgbh/nova/baby/divi_flash.html SAME

MITOSIS vs MEIOSIS CYTOKINESIS CYTOKINESIS II http://www.pbs.org/wgbh/nova/baby/divi_flash.html SAME http://www.pbs.org/wgbh/nova/baby/divi_flash.html

MAKING SPERM & EGGS

___________________= MAKING MATURE SPERM SPERMATOGENESIS ___________________= MAKING MATURE SPERM Mature & grow flagella

Sperm provides DNA All the starting nutrients, organelles, molecule building blocks, etc. have to come from the egg.

CYTOPLASM DIVIDES UNEVENLY OOGENESIS __________________ = MAKING a MATURE EGG Produces: 1 “good” egg 3 POLAR BODIES CYTOPLASM DIVIDES UNEVENLY

Sperm donates mostly DNA WHY MAKE ONLY ONE “GOOD” EGG? Sperm donates mostly DNA Most of the cell parts and nutrients needed for baby come from EGG! http://bestweekever.blogs.com/photos/uncategorized/imagemain_sperm_egg1_1.gif

After cell division, how many chromosomes are in the body cells of humans? 42 46 23 21

After cell division, how many chromosomes are in the body cells of humans? 42 46 Correct! 23 21

After cell division, how many chromosomes are in the sex cells of humans? 42 46 23 21

After cell division, how many chromosomes are in the sex cells of humans? 42 46 23 Correct 21

What events of meiosis allows for genetic recombination in meiosis? Crossing over Crossing over, independent assortment Synapsis tetrad

What events of meiosis allows for genetic recombination in meiosis? Crossing over Crossing over, independent assortment Correct!! Synapsis tetrad